Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 176 of 196

Corresponding author Samuel Were Department of Botany College of Pure and Applied Sciences Jomo Kenyatta University ofAgriculture and Technology Nairobi Kenya E-mail samaringogmailcom

2663-2187copy 2021 African Journal of Biological Sciences All rights reserved

African Journal of Biological Sciences

ISSN 2663-2187

Journal homepage httpwwwafjbscom

Biochar and vermicompost soil amendments reduce root rot disease ofcommon bean (Phaseolous Vulgaris L)

Samuel A Were1 Rama Narla2 E W Mutitu3 JW Muthomi4 Liza M Munyua5 Dries Roobroeck6 BernardVanlauwe7 and Janice E8

1Department of Botany College of Pure and Applied Sciences Jomo Kenyatta University of Agriculture and TechnologyNairobi Kenya and Department of Plant Science and Crop Protection University of Nairobi Nairobi Kenya E-mailsamaringogmailcom2Department of Plant Science and Crop Protection University of Nairobi Nairobi Kenya E-mail ramanarla9gmailcom3Department of Plant Science and Crop Protection University of Nairobi Nairobi Kenya E-mail mutituuonbiacke4Department of Plant Science and Crop Protection University of Nairobi Nairobi Kenya E-mail james_wanjohiyahoocom5Liza M Munyua Department of Plant Science and Crop Protection University of Nairobi Nairobi KenyaE-mail lmburagmailcom6International Institute of Tropical Agriculture (IITA) Nairobi co ICIPE Kasarani Nairobi Kenya E-mail DRoobroeckcgiarorg7International Institute of Tropical Agriculture (IITA) Nairobi co ICIPE Kasarani Nairobi Kenya E-mail BVanlauwecgiarorg8School of Integrative Plant Science College of Agriculture and Life Sciences Cornell University E-mail janicethiescornelledu

Research Paper Open Access

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196httpsdoiorg1033472AFJBS312021176-196

Volume 3 Issue 1 January 2021Received 15 August 2020Accepted 18 November 2020Published 01 January 2021doi 1033472AFJBS312021176-196

Article Info

AbstractCommon bean production is constrained by root rot complexes resulting to asmuch as 70 losses in Kenya This study sought to establish the effect of soilamendments biochar and vermicompost on root rot fungal pathogens of commonbean in Western Kenya Application of biochar vermicompost and fertilizerwere done in farmer fields in four agro ecological zones of Western Kenya priorto planting during the long rains of 2013 and 2014 No applications were done inthe shot rains seasons of 2013 and 2014 Plant emergence and disease incidencewas recorded in the field and disease severity determined in the laboratoryIsolation and identification of pathogens was done from treatment plots followinga two weeks and six weeks sampling after planting Pathogens isolated wereidentified using morphological characteristics Soil amendments positivelyinfluenced plant emergence Root rot disease incidence and severity was greatlyreduced up to 40 and 60 every season respectively Biochar and vermicomposttreatments reduced the population of fungal pathogens and also influenced thepopulations of beneficial microorganisms such as Trichoderma and Paecilomyceslilacinus Application of soil amendments increased yield by 46 and also soil pHand nutrients were increased In conclusion treatment application ofvermicompost and biochar reduce root rot disease and improve bean productivity

Keywords Fusarium solani Pythium ultimum Rhizoctonia solani Soil amendmentsbiochar vermicompost

copy 2021 African Journal of Biological SciencesThis is an open access article under the CC BY license(httpscreativecommonsorglicensesby40) which permits unrestricted use distribution

and reproduction in any medium provided you give appropriate credit to the original author(s)and the source provide a link to the Creative Commons license and indicate if changes were made

1 IntroductionCommon bean production in Kenya is faced by various constraints such as insect pests reduced soil fertilityenvironmental stress and diseases which are major constraints These constraints have led to low productionaveraging 220-670 kgha (Buruchara et al 2015) Alongside other diseases root rot is a major constraint to

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 177 of 196

bean production in the tropics It has been previously reported to cause total crop failure in western Kenya(Nzungize et al 2012) Root rots are caused by a complex of soil-borne fungal pathogens including Pythiumultimum Fusarium solani fsp phaseoli Macrophomina phaseolina and Rhizoctonia spp (Nzungize et al 2012 andMwangrsquoombe et al 2008) The root rot fungi persist saprophytically in the soil and on organic matter whenthere is no host or as resting spores making it difficult to manage the disease complex (Agrios 2005)

Options available for managing root rot complex of beans are limited and their effectiveness is often lowafter planting (Abawi and Pastor-corrales 1990) Broad range and highly specific fumigants are available toeffectively manage root rots Their toxicity to man and environment when not handled well as well as theirhigh cost has however limited their use (United Nations 2008 and Abawi et al 2006) At the same timeefficacy of the available seed dressing chemicals in the market is not sustainable This emanates from thedevelopment of resistance as a result of multiple pathogen genera found in most areas of production and theirdegradation following continuous use (Abawi and Pastor Corrales 1990 and Nolling 1991) Other limitationsto conventional methods of managing root rot pathogens include development of resistance by plant pathogensand lack of tolerant or resistant bean varieties to multiple diseases causing pathogens (Nzungize et al 2012)

Agronomic practices such as use of organic amendments have shown positive changes in root diseasedynamics and yield increase (Bailey and Lazarovits 2003) Different types of composts and biochar arerecognized to increase soil health They are also known to suppress soil-borne diseases caused by diversegenera such as Fusarium Pythium Rhizoctonia and Phytophthora (Mehta et al 2014 Sohi et al 2010 and Eladet al 2010) Biochar is a product of anaerobic thermal degradation of biomass while vermicompost is a humicsubstance produced through an accelerated composting process by the feeding of earthworms These are usedas soil amendments in management of root rot pathogens The suppressiveness of vermicompost and biocharis ascribed to a useful microbial community an improvement in growth and vigor of plant improved availabilityof nutrient systemic resistance induction or fungistatic capabilities of the vermicompost and biocharmodifications (Bonanomi et al 2017 and Graber et al 2014) Synergy of biochar and vermicompost has beenshown to improve fertility of soil growth of plants as well as increase the activity of beneficial microbes in therhizosphere (Agegnehu et al 2015 and Fischer and Glaser 2012) Some studies have however reportedadverse effects of different types of biochar on crop yield soil properties and beneficial soil micro biota(Mukherjee and Lal 2014) It is also not known whether the biochar effect remains protective over a number ofseasons in field situations since information on the longevity of these effects for soil borne pathogens has notbeen documented (Graber et al 2014) This study therefore aimed at determining the effect of sugarcanebagasse biochar and vermicompost on root rot diseases of common bean

2 Materials and methods

21 Production of soil amendments biochar and vermicompostPlant residues from sugarcane bagasse were sourced from Kibos Sugar Factory in Kisumu Kenya and sundried The bagasse was pyrolised to produce biochar (Laird 2008 and Lehmann 2007) using a metallicproduction kiln with a perforation at the base to allow for air flow and a chimney to expel the burning gasesBiochar was weighed and packed into 6 kgs gunny bags before application Vermicompost was produced atDudutech Naivasha Kenya from vegetable crop residue The plant debris were chopped and air dried for 7-10 days then placed into 30 centimeter deep rectangular troughs which had an initial population of 6000earth worms (Eisinia andrei) in 40 kgs of pre-decomposed crop material and soil mixture The crop residue wasspread evenly on the surface of the trough where it was decomposed by earth worms feeding on the plantdebris for a period of six weeks The resultant worm casting referred to as vermicompost was then analyzed fornutrition and chemical content at Dudutech Naivasha Kenya while biochar was analyzed for chemicalproperties at Crop Nutrition Laboratories Nairobi Kenya

22 Study site and experimental layoutThe study was an on farm multi locational trial in 60 farms spread out in three regions of North Teso Bungomaand Kakamega Kenya that covered four different agro ecological zones Lower midland humid (LM1) Lowermidland sub humid (LM2) Upper midland humid (UM1) and Upper midland semi humid (UM3) with analtitude range of 800 m to 1900 m above sea level (ASL) and temperatures of 18deg to 24 degC (Jaetzold et al 2005)All these regions receive a bimodal rainfall consisting of long rains from March to July and short rains fromSeptember to November allowing biannual cropping seasons The regions have varying soil types whichinclude acrisols gleysols regosols cambisols nitisols vertisols and ferralsols (Ralph et al 2005) The 60farms were selected from a sampling frame of 280 small holder bean growers in the three counties of westernKenya with history of common bean cultivation in the previous season under a technology transfer projectThe sample size was calculated following Nassiuma (2000) formula

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 178 of 196

Each field measuring 125 m by 215 m was subdivided into eight treatment plots each of 6 m by 5 m Asusceptible bean variety to root rot (Rosecoco or GLP2) from CIAT Maseno was used in the trial Treatmentsapplied were biochar vermicompost and sympal (NPK 02315) fertilizer (MEA) biochar and vermicompostbiochar and sympal vermicompost and sympal biochar vermicompost together with sympal and a controlwhere no amendment was applied Biochar and vermicompost were each applied at a rate of 2000 kgs ha-1

while Sympalreg fertilizer - NPK 0 2315 was applied at a rate of 300 kg ha-1 at planting Treatments were onlyapplied in the long rain seasons of 2013 and 2014 prior to planting Planting in the short rain seasons of 2013and 2014 were undertaken without application of treatments but the same plots were maintained to assess theresidual effect of the treatments on bean root rot The amendments were applied as a micro dose in the plantingfurrows then mixed with the soil prior to planting the bean seeds which were then covered with about 2 cm ofsoil The bean seed was planted at the rate of 40 kg ha-1 at a spacing of 60 cm times 15 cm giving a plant populationof 330 plants per treatment plot The experiment was carried out in a completely randomized design

23 Assessment for root rot disease incidence and severityRoot rot disease incidence was recorded as percentage of diseased plants showing root rot symptoms per plotat two after seedling emergence so as to observe both pre-emergence and post emergence damping off Beanplants infected with root rot were identified based on symptoms such as damping off yellowing of leavesstunted growth wilting brown discoloration on roots and dark brown to red colored lesions on roots Fivesymptomatic and asymptomatic plants were sampled from each plot at the end of the 2nd week after emergenceand used to determine the disease severity of root rot in each plot Scoring of disease severity was by visualassessment of necrotic lesions on roots and hypocotyls based on a rating scale of 1-9 as described by Abawiand Pastor-Corrales (1990) The rating used was 1 = no observable symptoms 3 = light discoloration withoutnecrotic lesions or 10 of hypocotyl and root tissues covered with lesions 5 = hypocotyls and root tissuescovered with lesions up to 25 but tissues remain firm 7 = considerable softening rotting and reduction ofthe root system accompanied by lesions covering approximately 50 of the hypocotyls and root tissues 9 =advanced stages of rotting approximately with 75 or more of the root tissues and hypocotyl affected as wellas extensive deterioration of the root system These scores were then converted to percentage severity index(Assefa et al 2014)

scaleonscoreMaximumscoredplantsofNoratingnumericalofSumIndexSeverityPercent

100

24 Isolation of root rot fungal pathogens from infected bean roots and rhizosphere soilFive root tissues from each treatment per farmer field were washed under running water Roots were then cutinto pieces measuring 1 cm and sterilized in 1 sodium hypochlorite then in 10 ethanol for 3 min The plantpieces were then rinsed in three changes of sterile distilled water then blot drying on sterile serviettes Theroots were then plated on PDA amended with 50 ppm streptomycin and incubated for 7-14 days at roomtemperature ranging between 25 ordmC and 28 ordmC

Rhizosphere soil samples were collected two weeks and six weeks after emergence and at harvest todetermine the fungal flora from each treatment plot Sampling was done at 10 points in each plot in a shape at a spacing of 15 m between the sampling points A composite soil sample weighing one kilogram wasthen taken from the 10 samples placed in well labeled polythene bag and brought to the laboratory at theUniversity of Nairobi and stored at 4 ordmC prior to isolation of root rot pathogens Three sub samples eachweighing 1 g were taken from each 1 kg of composite soil samples dissolved in 10 ml sterile distilled water inthree different universal bottles mixed by shaking for 1 min followed by a 10-fold serial dilution series for eachsample to achieve a 10-4 dilution One milliliter of 10-4 dilution was plated on potato dextrose agar amendedwith 0 ppm streptomycin sulphate antibiotic (PDA-HIMEDIA) medium using pour plate method Each dilutionwas replicated three times and incubated at room temperature for seven days Different fungal colonies werecounted and quantified per gram of soil

The fungi were then sub cultured on fresh PDA medium and upon identification different genera of fungiwere sub-cultured on different media Fusarium spp was sub-cultured on Spezieller Naumlhrstoffarmer Agar(SNA) (Nirenberg 1981) and PDA media Sporulation of cultures on SNA was achieved by incubation underUV light while those on PDA were incubated under normal 12 h photo period All cultures were incubated at

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 179 of 196

25 ordmC for 14- 21 days to study cultural characteristics of each fungus for their final identification Based onmorphological characteristics identification of Fusarium isolates was done to species level following keys byNelson et al (1983) and the Fusarium laboratory manual (Leslie and Summerell 2006) Identification of otherfungi was based on morphological and cultural features such as color of the colony growth type color ofmycelia and spore types (Zhou et al 2010) The colony forming units of each fungal type per gram of soil wasalso calculated by multiplying the number of colonies with the dilution factor Pythium sp were sub culturedon corn meal agar to observe the production of sporangia oogonia and antheridia that were used in identificationbased on keys by Plaats-Niterink (1981) and Dick (1990)

Relative isolation frequency was calculated for each genus using the formula by Gonzalez et al (1999) Allthe fungal isolates were preserved on PDA slants at 4 ordmC at the University of Nairobi for further identificationby gene sequencing

100() isolatesallofnumberTotal

genusaofisolatesofNumberFrequency

At the end of the fourth season soil samples were also analyzed using quantitative PCR to establish thepathogen load in comparison with the conventional isolation method

25 Effect of biochar and vermicompost on yield of common beanHarvesting was done from plants in the net plot measuring 2256 M2 The crop stand count for each plot wasrecorded before harvesting Total fresh weight of pods and hauls at harvest was recorded in the field Sampleswere randomly selected from each net plot and the pods per plant counted separated and weighed Thesewere later dried at 65 oC for 48 h at CIAT Maseno and the weights used to estimate yield parameters such as 100seed weight per plot and total seed yield per plot and later extrapolated to kgha

3 Data collection and analysisData on emergence was recorded 14 days after planting where the total number of plants that had emergedwas counted per treatment plot and expressed as percentages Disease incidence was determined by countingthe number of diseased plants in the net plot This was then divided by the total number of plants in the net plotmultiplied by 100 Data on disease severity was determined after scoring of diseased roots on a scale of 1 to 9for root rot symptoms Beans were harvested at physiological maturity and dry grains from each net plot wereweighed after drying at 65 ordmC for 24 h Data on fungal counts was collected following isolation from the plantand rhizosphere soil samples at 2nd 6th week and harvest while other data such as soil particle size percentagessoil pH and soil nutrient content were recorded following laboratory analysis These data was subjected toanalysis of variance (ANOVA) by GENSTAT version 14 and the Tukey test Least Significant Difference (LSD)was used for mean separation at 5 level of significance

4 Results

41 Physical and chemical characteristics of biochar and vermicompostThe two soil amendments analyzed varied in their composition Vermicompost had higher moisture contentthan biochar No volatile compounds or ash were found in vermicompost but were present in biochar fromsugarcane bagasse (Table 1) pH of the two amendments was found to be near neutral Electrical conductivitydry matter content and CN ratio were higher in SB biochar as compared to vermicompost Phosphorus was

Table 1 Characteristics of vermicompost and biochar

Amendment MC Volatiles Ash pH EC DM C N CN() () () (mScm) () () () ()

Vermicompost 482 NIL NIL 692 1 2 508 301 354 851

S B biochar 310 910 966 683 735 9690 6287 531 1185

Note MC ndash Moisture Content EC ndash Electrical Conductivity DM ndash Dry Matter C ndash Carbon N ndash Nitrogen CN ndash CarbonNitrogen ratio and S B biochar ndash Sugarcane bagasse biochar

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 180 of 196

the highest nutrient in the biochar as compared to other elements Sugarcane bagasse biochar had higherlevel of phosphorus than that of vermicompost while Potassium was more in vermicompost than in biochar(Table 2) Vermicompost had 25 Nutrients such as Magnesium Sulphur Manganese Iron and Boron werehigher in vermicompost while Sodium Zinc and Copper were highest in SB biochar

Table 2 Nutrient analysis of biochar and vermicompost

Amendment P K Ca Mg S Mn Fe B Na Zn Cu() () () () (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

Vermicompost 064 331 254 054 04 4100 66000 1010 14800 1850 178

S B biochar 101 073 na 037 003 369 4853 144 26683 5702 382

Note P ndash Phosphorus K ndash Potassium Ca ndash Calcium Mg ndash Magnesium S ndash Sulphur Mn ndash Manganese Fe ndash Iron B ndash BoronNa ndash Sodium Zn ndash Zinc Cu ndash Copper S B biochar ndash Sugarcane bagasse biochar ppm ndash parts per million NA ndash Notavailablepresent

42 Effect of soil amendments on plant emergenceSignificant differences were recorded among treatments in all the four seasons Interaction between treatmentsand agro ecological zones resulted in significant differences (p lt 005) in LM1 and UM1 The highest emergencewas recorded in treatment combination of biochar vermicompost and fertilizer in LM1 during the long rainseason while the lowest was recorded in vermicompost and fertilizer treatments in UM1 (Table 3) In the shortrain season of 2013 significant differences (p lt 005) were recorded for interaction in three AEZrsquos In the three

Table 3 Effect of different treatments on plant emergence () in different AEZrsquos of Western Kenya during

the long rains and short rains seasons of 2013

Treatments Long Rains Season 2013 Short Rains Season 2013

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 383c 603a 242c 608a 459c 841a 735a 815ab 711bc 775ab

Fertilizer 465bc 604a 258bc 628a 488b 889a 664b 714d 674bc 735c

Biochar 478bc 597a 347ab 663a 521b 857a 708ab 735cd 726ab 757bc

Biochar + Fertilizer 403bc 631a 234c 640a 477bc 854a 688ab 801abc 639c 746bc

Biochar +Vermicompost 499b 626a 250bc 671a 512ab 835a 704ab 827ab 696bc 765b

Biochar + 636a 605a 441a 627a 577a 815a 692ab 771bcd 619c 724cVermicompost +Fertilizer

Vermicompost 468bc 581a 217c 633a 474bc 814a 746a 873a 797a 808a

Vermicompost + 400bc 632a 209c 619a 465c 820a 650b 788bcd 622c 720cFertilizer

LSD Interaction 103 52 75 37Treatment times AEZ

CV 409 195

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 181 of 196

AEZrsquos the highest emergence was recorded in vermicompost treated plots in UM1 while the lowest wasrecorded in the vermicompost and fertilizer treated plots in UM3 Significant differences (p lt 005) were alsorecorded for collective treatments Treatment combination of biochar vermicompost and fertilizer had thehighest emergence in the long rains of 2013 while the lowest was recorded in non-amended control plots Inthe short rains season of 2013 vermicompost treated plots had the highest emergence while the vermicompostand fertilizer treated plots had the lowest emergence the differences being significant (p lt 005)

Significant differences (p lt 005) in plant emergence were also observed for treatments and their interactionswith AEZrsquos during the long and short rain season of 2014 (Table 4) The highest emergence was recorded inbiochar treated plots in LM1 while control and fertilizer treated plots in UM3 had the lowest plant emergencein the long rains of 2014 In the short rains of 2014 highest plant emergence was recorded in biochar andfertilizer treated plots at UM1 while the lowest was recorded in fertilized control plots at LM2 Significantdifference (p lt 005) in plant emergence was observed for the treatments across the AEZrsquos both in the 2014 longand short rains season The highest plant emergence was recorded in vermicompost treated plots in the twoseasons However the lowest plant emergence was observed in control plots amended with fertilizer in thelong rains of 2014 and in plots with a combination of biochar vermicompost and fertilizer in the short rains of2014

Table 4 Effect of different treatments on plant emergence () of common bean in different AEZrsquos of

Western Kenya during the long and short rains seasons of 2014

Treatments Long Rains Season 2014 Short Rains Season 2014

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 901a 772a 796b 784a 813ab 795c 691cd 859ab 746bc 773c

Fertilizer 870a 682b 819b 654d 756d 843abc 670d 855ab 741bc 777c

Biochar 922a 729ab 837b 776ab 816ab 883a 744bc 830b 783ab 810ab

Biochar + Fertilizer 860a 771a 847ab 697cd 794bc 873ab 744bc 895a 728bcd 810ab

Vermicompost 873a 771a 901a 769ab 827a 848abc 830a 840ab 826a 836a

Vermicompost + 906a 673b 847ab 690cd 779cd 817bc 755b 891a 675d 785bcFertilizer

Biochar + 890a 783a 861a 720bc 816ab 837abc 736bc 815b 714cd 776cVermicompost

Biochar + 891a 726ab 855ab 693cd 791bc 807c 708bcd 839ab 689cd 761cVermicompost +Fertilizer

LSD Interaction 62 31 57 28Treatment times AEZ

CV 152 141

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

43 Effect of soil amendments on incidence of root rot in Western KenyaRoot rot disease incidence was observed to significantly vary (p lt 005) with treatments and interactionsbetween treatments and AEZrsquos two weeks after planting (Table 5) During the short rains season of 2013 thehighest incidence among the treatments was recorded in vermicompost amended plots while the lowestincidence was recorded in biochar and fertilizer treatment combinations and in vermicompost and fertilizerstreatment combinations though the differences were not significant The same trend was observed in the shortrains season of 2014 with the differences also not being significant During the long rains of 2014 significant

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 178 of 196

Each field measuring 125 m by 215 m was subdivided into eight treatment plots each of 6 m by 5 m Asusceptible bean variety to root rot (Rosecoco or GLP2) from CIAT Maseno was used in the trial Treatmentsapplied were biochar vermicompost and sympal (NPK 02315) fertilizer (MEA) biochar and vermicompostbiochar and sympal vermicompost and sympal biochar vermicompost together with sympal and a controlwhere no amendment was applied Biochar and vermicompost were each applied at a rate of 2000 kgs ha-1

while Sympalreg fertilizer - NPK 0 2315 was applied at a rate of 300 kg ha-1 at planting Treatments were onlyapplied in the long rain seasons of 2013 and 2014 prior to planting Planting in the short rain seasons of 2013and 2014 were undertaken without application of treatments but the same plots were maintained to assess theresidual effect of the treatments on bean root rot The amendments were applied as a micro dose in the plantingfurrows then mixed with the soil prior to planting the bean seeds which were then covered with about 2 cm ofsoil The bean seed was planted at the rate of 40 kg ha-1 at a spacing of 60 cm times 15 cm giving a plant populationof 330 plants per treatment plot The experiment was carried out in a completely randomized design

23 Assessment for root rot disease incidence and severityRoot rot disease incidence was recorded as percentage of diseased plants showing root rot symptoms per plotat two after seedling emergence so as to observe both pre-emergence and post emergence damping off Beanplants infected with root rot were identified based on symptoms such as damping off yellowing of leavesstunted growth wilting brown discoloration on roots and dark brown to red colored lesions on roots Fivesymptomatic and asymptomatic plants were sampled from each plot at the end of the 2nd week after emergenceand used to determine the disease severity of root rot in each plot Scoring of disease severity was by visualassessment of necrotic lesions on roots and hypocotyls based on a rating scale of 1-9 as described by Abawiand Pastor-Corrales (1990) The rating used was 1 = no observable symptoms 3 = light discoloration withoutnecrotic lesions or 10 of hypocotyl and root tissues covered with lesions 5 = hypocotyls and root tissuescovered with lesions up to 25 but tissues remain firm 7 = considerable softening rotting and reduction ofthe root system accompanied by lesions covering approximately 50 of the hypocotyls and root tissues 9 =advanced stages of rotting approximately with 75 or more of the root tissues and hypocotyl affected as wellas extensive deterioration of the root system These scores were then converted to percentage severity index(Assefa et al 2014)

scaleonscoreMaximumscoredplantsofNoratingnumericalofSumIndexSeverityPercent

100

24 Isolation of root rot fungal pathogens from infected bean roots and rhizosphere soilFive root tissues from each treatment per farmer field were washed under running water Roots were then cutinto pieces measuring 1 cm and sterilized in 1 sodium hypochlorite then in 10 ethanol for 3 min The plantpieces were then rinsed in three changes of sterile distilled water then blot drying on sterile serviettes Theroots were then plated on PDA amended with 50 ppm streptomycin and incubated for 7-14 days at roomtemperature ranging between 25 ordmC and 28 ordmC

Rhizosphere soil samples were collected two weeks and six weeks after emergence and at harvest todetermine the fungal flora from each treatment plot Sampling was done at 10 points in each plot in a shape at a spacing of 15 m between the sampling points A composite soil sample weighing one kilogram wasthen taken from the 10 samples placed in well labeled polythene bag and brought to the laboratory at theUniversity of Nairobi and stored at 4 ordmC prior to isolation of root rot pathogens Three sub samples eachweighing 1 g were taken from each 1 kg of composite soil samples dissolved in 10 ml sterile distilled water inthree different universal bottles mixed by shaking for 1 min followed by a 10-fold serial dilution series for eachsample to achieve a 10-4 dilution One milliliter of 10-4 dilution was plated on potato dextrose agar amendedwith 0 ppm streptomycin sulphate antibiotic (PDA-HIMEDIA) medium using pour plate method Each dilutionwas replicated three times and incubated at room temperature for seven days Different fungal colonies werecounted and quantified per gram of soil

The fungi were then sub cultured on fresh PDA medium and upon identification different genera of fungiwere sub-cultured on different media Fusarium spp was sub-cultured on Spezieller Naumlhrstoffarmer Agar(SNA) (Nirenberg 1981) and PDA media Sporulation of cultures on SNA was achieved by incubation underUV light while those on PDA were incubated under normal 12 h photo period All cultures were incubated at

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 179 of 196

25 ordmC for 14- 21 days to study cultural characteristics of each fungus for their final identification Based onmorphological characteristics identification of Fusarium isolates was done to species level following keys byNelson et al (1983) and the Fusarium laboratory manual (Leslie and Summerell 2006) Identification of otherfungi was based on morphological and cultural features such as color of the colony growth type color ofmycelia and spore types (Zhou et al 2010) The colony forming units of each fungal type per gram of soil wasalso calculated by multiplying the number of colonies with the dilution factor Pythium sp were sub culturedon corn meal agar to observe the production of sporangia oogonia and antheridia that were used in identificationbased on keys by Plaats-Niterink (1981) and Dick (1990)

Relative isolation frequency was calculated for each genus using the formula by Gonzalez et al (1999) Allthe fungal isolates were preserved on PDA slants at 4 ordmC at the University of Nairobi for further identificationby gene sequencing

100() isolatesallofnumberTotal

genusaofisolatesofNumberFrequency

At the end of the fourth season soil samples were also analyzed using quantitative PCR to establish thepathogen load in comparison with the conventional isolation method

25 Effect of biochar and vermicompost on yield of common beanHarvesting was done from plants in the net plot measuring 2256 M2 The crop stand count for each plot wasrecorded before harvesting Total fresh weight of pods and hauls at harvest was recorded in the field Sampleswere randomly selected from each net plot and the pods per plant counted separated and weighed Thesewere later dried at 65 oC for 48 h at CIAT Maseno and the weights used to estimate yield parameters such as 100seed weight per plot and total seed yield per plot and later extrapolated to kgha

3 Data collection and analysisData on emergence was recorded 14 days after planting where the total number of plants that had emergedwas counted per treatment plot and expressed as percentages Disease incidence was determined by countingthe number of diseased plants in the net plot This was then divided by the total number of plants in the net plotmultiplied by 100 Data on disease severity was determined after scoring of diseased roots on a scale of 1 to 9for root rot symptoms Beans were harvested at physiological maturity and dry grains from each net plot wereweighed after drying at 65 ordmC for 24 h Data on fungal counts was collected following isolation from the plantand rhizosphere soil samples at 2nd 6th week and harvest while other data such as soil particle size percentagessoil pH and soil nutrient content were recorded following laboratory analysis These data was subjected toanalysis of variance (ANOVA) by GENSTAT version 14 and the Tukey test Least Significant Difference (LSD)was used for mean separation at 5 level of significance

4 Results

41 Physical and chemical characteristics of biochar and vermicompostThe two soil amendments analyzed varied in their composition Vermicompost had higher moisture contentthan biochar No volatile compounds or ash were found in vermicompost but were present in biochar fromsugarcane bagasse (Table 1) pH of the two amendments was found to be near neutral Electrical conductivitydry matter content and CN ratio were higher in SB biochar as compared to vermicompost Phosphorus was

Table 1 Characteristics of vermicompost and biochar

Amendment MC Volatiles Ash pH EC DM C N CN() () () (mScm) () () () ()

Vermicompost 482 NIL NIL 692 1 2 508 301 354 851

S B biochar 310 910 966 683 735 9690 6287 531 1185

Note MC ndash Moisture Content EC ndash Electrical Conductivity DM ndash Dry Matter C ndash Carbon N ndash Nitrogen CN ndash CarbonNitrogen ratio and S B biochar ndash Sugarcane bagasse biochar

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 180 of 196

the highest nutrient in the biochar as compared to other elements Sugarcane bagasse biochar had higherlevel of phosphorus than that of vermicompost while Potassium was more in vermicompost than in biochar(Table 2) Vermicompost had 25 Nutrients such as Magnesium Sulphur Manganese Iron and Boron werehigher in vermicompost while Sodium Zinc and Copper were highest in SB biochar

Table 2 Nutrient analysis of biochar and vermicompost

Amendment P K Ca Mg S Mn Fe B Na Zn Cu() () () () (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

Vermicompost 064 331 254 054 04 4100 66000 1010 14800 1850 178

S B biochar 101 073 na 037 003 369 4853 144 26683 5702 382

Note P ndash Phosphorus K ndash Potassium Ca ndash Calcium Mg ndash Magnesium S ndash Sulphur Mn ndash Manganese Fe ndash Iron B ndash BoronNa ndash Sodium Zn ndash Zinc Cu ndash Copper S B biochar ndash Sugarcane bagasse biochar ppm ndash parts per million NA ndash Notavailablepresent

42 Effect of soil amendments on plant emergenceSignificant differences were recorded among treatments in all the four seasons Interaction between treatmentsand agro ecological zones resulted in significant differences (p lt 005) in LM1 and UM1 The highest emergencewas recorded in treatment combination of biochar vermicompost and fertilizer in LM1 during the long rainseason while the lowest was recorded in vermicompost and fertilizer treatments in UM1 (Table 3) In the shortrain season of 2013 significant differences (p lt 005) were recorded for interaction in three AEZrsquos In the three

Table 3 Effect of different treatments on plant emergence () in different AEZrsquos of Western Kenya during

the long rains and short rains seasons of 2013

Treatments Long Rains Season 2013 Short Rains Season 2013

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 383c 603a 242c 608a 459c 841a 735a 815ab 711bc 775ab

Fertilizer 465bc 604a 258bc 628a 488b 889a 664b 714d 674bc 735c

Biochar 478bc 597a 347ab 663a 521b 857a 708ab 735cd 726ab 757bc

Biochar + Fertilizer 403bc 631a 234c 640a 477bc 854a 688ab 801abc 639c 746bc

Biochar +Vermicompost 499b 626a 250bc 671a 512ab 835a 704ab 827ab 696bc 765b

Biochar + 636a 605a 441a 627a 577a 815a 692ab 771bcd 619c 724cVermicompost +Fertilizer

Vermicompost 468bc 581a 217c 633a 474bc 814a 746a 873a 797a 808a

Vermicompost + 400bc 632a 209c 619a 465c 820a 650b 788bcd 622c 720cFertilizer

LSD Interaction 103 52 75 37Treatment times AEZ

CV 409 195

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 181 of 196

AEZrsquos the highest emergence was recorded in vermicompost treated plots in UM1 while the lowest wasrecorded in the vermicompost and fertilizer treated plots in UM3 Significant differences (p lt 005) were alsorecorded for collective treatments Treatment combination of biochar vermicompost and fertilizer had thehighest emergence in the long rains of 2013 while the lowest was recorded in non-amended control plots Inthe short rains season of 2013 vermicompost treated plots had the highest emergence while the vermicompostand fertilizer treated plots had the lowest emergence the differences being significant (p lt 005)

Significant differences (p lt 005) in plant emergence were also observed for treatments and their interactionswith AEZrsquos during the long and short rain season of 2014 (Table 4) The highest emergence was recorded inbiochar treated plots in LM1 while control and fertilizer treated plots in UM3 had the lowest plant emergencein the long rains of 2014 In the short rains of 2014 highest plant emergence was recorded in biochar andfertilizer treated plots at UM1 while the lowest was recorded in fertilized control plots at LM2 Significantdifference (p lt 005) in plant emergence was observed for the treatments across the AEZrsquos both in the 2014 longand short rains season The highest plant emergence was recorded in vermicompost treated plots in the twoseasons However the lowest plant emergence was observed in control plots amended with fertilizer in thelong rains of 2014 and in plots with a combination of biochar vermicompost and fertilizer in the short rains of2014

Table 4 Effect of different treatments on plant emergence () of common bean in different AEZrsquos of

Western Kenya during the long and short rains seasons of 2014

Treatments Long Rains Season 2014 Short Rains Season 2014

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 901a 772a 796b 784a 813ab 795c 691cd 859ab 746bc 773c

Fertilizer 870a 682b 819b 654d 756d 843abc 670d 855ab 741bc 777c

Biochar 922a 729ab 837b 776ab 816ab 883a 744bc 830b 783ab 810ab

Biochar + Fertilizer 860a 771a 847ab 697cd 794bc 873ab 744bc 895a 728bcd 810ab

Vermicompost 873a 771a 901a 769ab 827a 848abc 830a 840ab 826a 836a

Vermicompost + 906a 673b 847ab 690cd 779cd 817bc 755b 891a 675d 785bcFertilizer

Biochar + 890a 783a 861a 720bc 816ab 837abc 736bc 815b 714cd 776cVermicompost

Biochar + 891a 726ab 855ab 693cd 791bc 807c 708bcd 839ab 689cd 761cVermicompost +Fertilizer

LSD Interaction 62 31 57 28Treatment times AEZ

CV 152 141

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

43 Effect of soil amendments on incidence of root rot in Western KenyaRoot rot disease incidence was observed to significantly vary (p lt 005) with treatments and interactionsbetween treatments and AEZrsquos two weeks after planting (Table 5) During the short rains season of 2013 thehighest incidence among the treatments was recorded in vermicompost amended plots while the lowestincidence was recorded in biochar and fertilizer treatment combinations and in vermicompost and fertilizerstreatment combinations though the differences were not significant The same trend was observed in the shortrains season of 2014 with the differences also not being significant During the long rains of 2014 significant

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

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York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 179 of 196

25 ordmC for 14- 21 days to study cultural characteristics of each fungus for their final identification Based onmorphological characteristics identification of Fusarium isolates was done to species level following keys byNelson et al (1983) and the Fusarium laboratory manual (Leslie and Summerell 2006) Identification of otherfungi was based on morphological and cultural features such as color of the colony growth type color ofmycelia and spore types (Zhou et al 2010) The colony forming units of each fungal type per gram of soil wasalso calculated by multiplying the number of colonies with the dilution factor Pythium sp were sub culturedon corn meal agar to observe the production of sporangia oogonia and antheridia that were used in identificationbased on keys by Plaats-Niterink (1981) and Dick (1990)

Relative isolation frequency was calculated for each genus using the formula by Gonzalez et al (1999) Allthe fungal isolates were preserved on PDA slants at 4 ordmC at the University of Nairobi for further identificationby gene sequencing

100() isolatesallofnumberTotal

genusaofisolatesofNumberFrequency

At the end of the fourth season soil samples were also analyzed using quantitative PCR to establish thepathogen load in comparison with the conventional isolation method

25 Effect of biochar and vermicompost on yield of common beanHarvesting was done from plants in the net plot measuring 2256 M2 The crop stand count for each plot wasrecorded before harvesting Total fresh weight of pods and hauls at harvest was recorded in the field Sampleswere randomly selected from each net plot and the pods per plant counted separated and weighed Thesewere later dried at 65 oC for 48 h at CIAT Maseno and the weights used to estimate yield parameters such as 100seed weight per plot and total seed yield per plot and later extrapolated to kgha

3 Data collection and analysisData on emergence was recorded 14 days after planting where the total number of plants that had emergedwas counted per treatment plot and expressed as percentages Disease incidence was determined by countingthe number of diseased plants in the net plot This was then divided by the total number of plants in the net plotmultiplied by 100 Data on disease severity was determined after scoring of diseased roots on a scale of 1 to 9for root rot symptoms Beans were harvested at physiological maturity and dry grains from each net plot wereweighed after drying at 65 ordmC for 24 h Data on fungal counts was collected following isolation from the plantand rhizosphere soil samples at 2nd 6th week and harvest while other data such as soil particle size percentagessoil pH and soil nutrient content were recorded following laboratory analysis These data was subjected toanalysis of variance (ANOVA) by GENSTAT version 14 and the Tukey test Least Significant Difference (LSD)was used for mean separation at 5 level of significance

4 Results

41 Physical and chemical characteristics of biochar and vermicompostThe two soil amendments analyzed varied in their composition Vermicompost had higher moisture contentthan biochar No volatile compounds or ash were found in vermicompost but were present in biochar fromsugarcane bagasse (Table 1) pH of the two amendments was found to be near neutral Electrical conductivitydry matter content and CN ratio were higher in SB biochar as compared to vermicompost Phosphorus was

Table 1 Characteristics of vermicompost and biochar

Amendment MC Volatiles Ash pH EC DM C N CN() () () (mScm) () () () ()

Vermicompost 482 NIL NIL 692 1 2 508 301 354 851

S B biochar 310 910 966 683 735 9690 6287 531 1185

Note MC ndash Moisture Content EC ndash Electrical Conductivity DM ndash Dry Matter C ndash Carbon N ndash Nitrogen CN ndash CarbonNitrogen ratio and S B biochar ndash Sugarcane bagasse biochar

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 180 of 196

the highest nutrient in the biochar as compared to other elements Sugarcane bagasse biochar had higherlevel of phosphorus than that of vermicompost while Potassium was more in vermicompost than in biochar(Table 2) Vermicompost had 25 Nutrients such as Magnesium Sulphur Manganese Iron and Boron werehigher in vermicompost while Sodium Zinc and Copper were highest in SB biochar

Table 2 Nutrient analysis of biochar and vermicompost

Amendment P K Ca Mg S Mn Fe B Na Zn Cu() () () () (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

Vermicompost 064 331 254 054 04 4100 66000 1010 14800 1850 178

S B biochar 101 073 na 037 003 369 4853 144 26683 5702 382

Note P ndash Phosphorus K ndash Potassium Ca ndash Calcium Mg ndash Magnesium S ndash Sulphur Mn ndash Manganese Fe ndash Iron B ndash BoronNa ndash Sodium Zn ndash Zinc Cu ndash Copper S B biochar ndash Sugarcane bagasse biochar ppm ndash parts per million NA ndash Notavailablepresent

42 Effect of soil amendments on plant emergenceSignificant differences were recorded among treatments in all the four seasons Interaction between treatmentsand agro ecological zones resulted in significant differences (p lt 005) in LM1 and UM1 The highest emergencewas recorded in treatment combination of biochar vermicompost and fertilizer in LM1 during the long rainseason while the lowest was recorded in vermicompost and fertilizer treatments in UM1 (Table 3) In the shortrain season of 2013 significant differences (p lt 005) were recorded for interaction in three AEZrsquos In the three

Table 3 Effect of different treatments on plant emergence () in different AEZrsquos of Western Kenya during

the long rains and short rains seasons of 2013

Treatments Long Rains Season 2013 Short Rains Season 2013

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 383c 603a 242c 608a 459c 841a 735a 815ab 711bc 775ab

Fertilizer 465bc 604a 258bc 628a 488b 889a 664b 714d 674bc 735c

Biochar 478bc 597a 347ab 663a 521b 857a 708ab 735cd 726ab 757bc

Biochar + Fertilizer 403bc 631a 234c 640a 477bc 854a 688ab 801abc 639c 746bc

Biochar +Vermicompost 499b 626a 250bc 671a 512ab 835a 704ab 827ab 696bc 765b

Biochar + 636a 605a 441a 627a 577a 815a 692ab 771bcd 619c 724cVermicompost +Fertilizer

Vermicompost 468bc 581a 217c 633a 474bc 814a 746a 873a 797a 808a

Vermicompost + 400bc 632a 209c 619a 465c 820a 650b 788bcd 622c 720cFertilizer

LSD Interaction 103 52 75 37Treatment times AEZ

CV 409 195

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 181 of 196

AEZrsquos the highest emergence was recorded in vermicompost treated plots in UM1 while the lowest wasrecorded in the vermicompost and fertilizer treated plots in UM3 Significant differences (p lt 005) were alsorecorded for collective treatments Treatment combination of biochar vermicompost and fertilizer had thehighest emergence in the long rains of 2013 while the lowest was recorded in non-amended control plots Inthe short rains season of 2013 vermicompost treated plots had the highest emergence while the vermicompostand fertilizer treated plots had the lowest emergence the differences being significant (p lt 005)

Significant differences (p lt 005) in plant emergence were also observed for treatments and their interactionswith AEZrsquos during the long and short rain season of 2014 (Table 4) The highest emergence was recorded inbiochar treated plots in LM1 while control and fertilizer treated plots in UM3 had the lowest plant emergencein the long rains of 2014 In the short rains of 2014 highest plant emergence was recorded in biochar andfertilizer treated plots at UM1 while the lowest was recorded in fertilized control plots at LM2 Significantdifference (p lt 005) in plant emergence was observed for the treatments across the AEZrsquos both in the 2014 longand short rains season The highest plant emergence was recorded in vermicompost treated plots in the twoseasons However the lowest plant emergence was observed in control plots amended with fertilizer in thelong rains of 2014 and in plots with a combination of biochar vermicompost and fertilizer in the short rains of2014

Table 4 Effect of different treatments on plant emergence () of common bean in different AEZrsquos of

Western Kenya during the long and short rains seasons of 2014

Treatments Long Rains Season 2014 Short Rains Season 2014

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 901a 772a 796b 784a 813ab 795c 691cd 859ab 746bc 773c

Fertilizer 870a 682b 819b 654d 756d 843abc 670d 855ab 741bc 777c

Biochar 922a 729ab 837b 776ab 816ab 883a 744bc 830b 783ab 810ab

Biochar + Fertilizer 860a 771a 847ab 697cd 794bc 873ab 744bc 895a 728bcd 810ab

Vermicompost 873a 771a 901a 769ab 827a 848abc 830a 840ab 826a 836a

Vermicompost + 906a 673b 847ab 690cd 779cd 817bc 755b 891a 675d 785bcFertilizer

Biochar + 890a 783a 861a 720bc 816ab 837abc 736bc 815b 714cd 776cVermicompost

Biochar + 891a 726ab 855ab 693cd 791bc 807c 708bcd 839ab 689cd 761cVermicompost +Fertilizer

LSD Interaction 62 31 57 28Treatment times AEZ

CV 152 141

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

43 Effect of soil amendments on incidence of root rot in Western KenyaRoot rot disease incidence was observed to significantly vary (p lt 005) with treatments and interactionsbetween treatments and AEZrsquos two weeks after planting (Table 5) During the short rains season of 2013 thehighest incidence among the treatments was recorded in vermicompost amended plots while the lowestincidence was recorded in biochar and fertilizer treatment combinations and in vermicompost and fertilizerstreatment combinations though the differences were not significant The same trend was observed in the shortrains season of 2014 with the differences also not being significant During the long rains of 2014 significant

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 180 of 196

the highest nutrient in the biochar as compared to other elements Sugarcane bagasse biochar had higherlevel of phosphorus than that of vermicompost while Potassium was more in vermicompost than in biochar(Table 2) Vermicompost had 25 Nutrients such as Magnesium Sulphur Manganese Iron and Boron werehigher in vermicompost while Sodium Zinc and Copper were highest in SB biochar

Table 2 Nutrient analysis of biochar and vermicompost

Amendment P K Ca Mg S Mn Fe B Na Zn Cu() () () () (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

Vermicompost 064 331 254 054 04 4100 66000 1010 14800 1850 178

S B biochar 101 073 na 037 003 369 4853 144 26683 5702 382

Note P ndash Phosphorus K ndash Potassium Ca ndash Calcium Mg ndash Magnesium S ndash Sulphur Mn ndash Manganese Fe ndash Iron B ndash BoronNa ndash Sodium Zn ndash Zinc Cu ndash Copper S B biochar ndash Sugarcane bagasse biochar ppm ndash parts per million NA ndash Notavailablepresent

42 Effect of soil amendments on plant emergenceSignificant differences were recorded among treatments in all the four seasons Interaction between treatmentsand agro ecological zones resulted in significant differences (p lt 005) in LM1 and UM1 The highest emergencewas recorded in treatment combination of biochar vermicompost and fertilizer in LM1 during the long rainseason while the lowest was recorded in vermicompost and fertilizer treatments in UM1 (Table 3) In the shortrain season of 2013 significant differences (p lt 005) were recorded for interaction in three AEZrsquos In the three

Table 3 Effect of different treatments on plant emergence () in different AEZrsquos of Western Kenya during

the long rains and short rains seasons of 2013

Treatments Long Rains Season 2013 Short Rains Season 2013

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 383c 603a 242c 608a 459c 841a 735a 815ab 711bc 775ab

Fertilizer 465bc 604a 258bc 628a 488b 889a 664b 714d 674bc 735c

Biochar 478bc 597a 347ab 663a 521b 857a 708ab 735cd 726ab 757bc

Biochar + Fertilizer 403bc 631a 234c 640a 477bc 854a 688ab 801abc 639c 746bc

Biochar +Vermicompost 499b 626a 250bc 671a 512ab 835a 704ab 827ab 696bc 765b

Biochar + 636a 605a 441a 627a 577a 815a 692ab 771bcd 619c 724cVermicompost +Fertilizer

Vermicompost 468bc 581a 217c 633a 474bc 814a 746a 873a 797a 808a

Vermicompost + 400bc 632a 209c 619a 465c 820a 650b 788bcd 622c 720cFertilizer

LSD Interaction 103 52 75 37Treatment times AEZ

CV 409 195

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 181 of 196

AEZrsquos the highest emergence was recorded in vermicompost treated plots in UM1 while the lowest wasrecorded in the vermicompost and fertilizer treated plots in UM3 Significant differences (p lt 005) were alsorecorded for collective treatments Treatment combination of biochar vermicompost and fertilizer had thehighest emergence in the long rains of 2013 while the lowest was recorded in non-amended control plots Inthe short rains season of 2013 vermicompost treated plots had the highest emergence while the vermicompostand fertilizer treated plots had the lowest emergence the differences being significant (p lt 005)

Significant differences (p lt 005) in plant emergence were also observed for treatments and their interactionswith AEZrsquos during the long and short rain season of 2014 (Table 4) The highest emergence was recorded inbiochar treated plots in LM1 while control and fertilizer treated plots in UM3 had the lowest plant emergencein the long rains of 2014 In the short rains of 2014 highest plant emergence was recorded in biochar andfertilizer treated plots at UM1 while the lowest was recorded in fertilized control plots at LM2 Significantdifference (p lt 005) in plant emergence was observed for the treatments across the AEZrsquos both in the 2014 longand short rains season The highest plant emergence was recorded in vermicompost treated plots in the twoseasons However the lowest plant emergence was observed in control plots amended with fertilizer in thelong rains of 2014 and in plots with a combination of biochar vermicompost and fertilizer in the short rains of2014

Table 4 Effect of different treatments on plant emergence () of common bean in different AEZrsquos of

Western Kenya during the long and short rains seasons of 2014

Treatments Long Rains Season 2014 Short Rains Season 2014

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 901a 772a 796b 784a 813ab 795c 691cd 859ab 746bc 773c

Fertilizer 870a 682b 819b 654d 756d 843abc 670d 855ab 741bc 777c

Biochar 922a 729ab 837b 776ab 816ab 883a 744bc 830b 783ab 810ab

Biochar + Fertilizer 860a 771a 847ab 697cd 794bc 873ab 744bc 895a 728bcd 810ab

Vermicompost 873a 771a 901a 769ab 827a 848abc 830a 840ab 826a 836a

Vermicompost + 906a 673b 847ab 690cd 779cd 817bc 755b 891a 675d 785bcFertilizer

Biochar + 890a 783a 861a 720bc 816ab 837abc 736bc 815b 714cd 776cVermicompost

Biochar + 891a 726ab 855ab 693cd 791bc 807c 708bcd 839ab 689cd 761cVermicompost +Fertilizer

LSD Interaction 62 31 57 28Treatment times AEZ

CV 152 141

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

43 Effect of soil amendments on incidence of root rot in Western KenyaRoot rot disease incidence was observed to significantly vary (p lt 005) with treatments and interactionsbetween treatments and AEZrsquos two weeks after planting (Table 5) During the short rains season of 2013 thehighest incidence among the treatments was recorded in vermicompost amended plots while the lowestincidence was recorded in biochar and fertilizer treatment combinations and in vermicompost and fertilizerstreatment combinations though the differences were not significant The same trend was observed in the shortrains season of 2014 with the differences also not being significant During the long rains of 2014 significant

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 181 of 196

AEZrsquos the highest emergence was recorded in vermicompost treated plots in UM1 while the lowest wasrecorded in the vermicompost and fertilizer treated plots in UM3 Significant differences (p lt 005) were alsorecorded for collective treatments Treatment combination of biochar vermicompost and fertilizer had thehighest emergence in the long rains of 2013 while the lowest was recorded in non-amended control plots Inthe short rains season of 2013 vermicompost treated plots had the highest emergence while the vermicompostand fertilizer treated plots had the lowest emergence the differences being significant (p lt 005)

Significant differences (p lt 005) in plant emergence were also observed for treatments and their interactionswith AEZrsquos during the long and short rain season of 2014 (Table 4) The highest emergence was recorded inbiochar treated plots in LM1 while control and fertilizer treated plots in UM3 had the lowest plant emergencein the long rains of 2014 In the short rains of 2014 highest plant emergence was recorded in biochar andfertilizer treated plots at UM1 while the lowest was recorded in fertilized control plots at LM2 Significantdifference (p lt 005) in plant emergence was observed for the treatments across the AEZrsquos both in the 2014 longand short rains season The highest plant emergence was recorded in vermicompost treated plots in the twoseasons However the lowest plant emergence was observed in control plots amended with fertilizer in thelong rains of 2014 and in plots with a combination of biochar vermicompost and fertilizer in the short rains of2014

Table 4 Effect of different treatments on plant emergence () of common bean in different AEZrsquos of

Western Kenya during the long and short rains seasons of 2014

Treatments Long Rains Season 2014 Short Rains Season 2014

AEZ LM1 LM2 UM1 UM3 Trt Means LM1 LM2 UM1 UM3 Trt Means

Control 901a 772a 796b 784a 813ab 795c 691cd 859ab 746bc 773c

Fertilizer 870a 682b 819b 654d 756d 843abc 670d 855ab 741bc 777c

Biochar 922a 729ab 837b 776ab 816ab 883a 744bc 830b 783ab 810ab

Biochar + Fertilizer 860a 771a 847ab 697cd 794bc 873ab 744bc 895a 728bcd 810ab

Vermicompost 873a 771a 901a 769ab 827a 848abc 830a 840ab 826a 836a

Vermicompost + 906a 673b 847ab 690cd 779cd 817bc 755b 891a 675d 785bcFertilizer

Biochar + 890a 783a 861a 720bc 816ab 837abc 736bc 815b 714cd 776cVermicompost

Biochar + 891a 726ab 855ab 693cd 791bc 807c 708bcd 839ab 689cd 761cVermicompost +Fertilizer

LSD Interaction 62 31 57 28Treatment times AEZ

CV 152 141

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

43 Effect of soil amendments on incidence of root rot in Western KenyaRoot rot disease incidence was observed to significantly vary (p lt 005) with treatments and interactionsbetween treatments and AEZrsquos two weeks after planting (Table 5) During the short rains season of 2013 thehighest incidence among the treatments was recorded in vermicompost amended plots while the lowestincidence was recorded in biochar and fertilizer treatment combinations and in vermicompost and fertilizerstreatment combinations though the differences were not significant The same trend was observed in the shortrains season of 2014 with the differences also not being significant During the long rains of 2014 significant

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 182 of 196

Table 5 Effect of different treatments on incidence () of bean root rot at two weeks of plant growth in differentAEZrsquos of Western Kenya

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 06a 10b 17ab 31a 16ab 06a 27a 11ab 21a 16a 07a 15b 12ab 39a 18ab

Fertilizer 03a 13b 11ab 20a 12ab 04a 23ab 13a 23a 16a 06a 17b 12ab 23b 14ab

Biochar 10a 14b 20a 20a 16ab 10a 20b 07ab 13b 12bc 12a 20ab 25a 25ab 21a

Biochar + Fertilizer 06a 11b 04b 15b 09b 04a 18bc 07ab 22a 13ab 08a 13b 06b 21b 12b

Vermicompost 11a 35a 08ab 15b 17a 04a 15c 07ab 14b 10bc 14a 33a 16ab 21b 21a

Vermicompost +

Fertilizer 04a 12b 06b 12b 09b 07a 20b 11ab 09b 12bc 05a 18b 09b 19b 13b

Biochar +

Vermicompost 13a 05b 17ab 23ab 14ab 06a 13c 05b 11b 09c 19a 10b 19ab 29ab 19ab

Biochar +

Vermicompost +

Fertilizer 15a 07b 07ab 18ab 12ab 04a 18bc 12a 13b 12bc 19a 13b 10b 25ab 17ab

LSD Inter 13 06 14

Trt x AEZ

LSD Treatments 07 03 07

CV 1953 987 1603

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

differences (p lt 005) were observed among treatments Plots with treatment combinations of biochar andvermicompost resulted in a 40 reduction in disease incidence when compared to the disease incidence in thecontrol plots Interaction between the treatments and AEZrsquos resulted to significant differences (p lt 005) inLM2 UM1 and UM3 in three seasons In the short rains season of 2013 the highest incidence was recorded invermicompost treated plots in LM2 while the lowest was recorded in biochar and fertilizer treated plots inUMI The same trend was observed in the short rains season of 2014 though control plots in UM3 had thehighest incidence of disease During the long rains of 2014 the highest disease incidence was recorded incontrol plots of LM2

44 Effect of soil amendments on bean root rot severity in Western KenyaAddition of soil amendments had an effect on the root rot disease severity at two weeks six weeks and atharvest Significant differences (p lt 005) were observed in percent severity index (PSI) among the treatmentsand their interaction with AEZrsquos two weeks after planting in three rain seasons (Table 6) In the short rainseason of 2013 the highest PSI among treatments was recorded in control plots and the lowest was recordedin vermicompost treated plots The same was observed among treatments during the long rains season of 2014and short rains of 2014 with the lowest PSI recorded in plots amended with a combination of biochar andvermicompost Treatment interaction with AEZrsquos had the highest PSI recorded in control plots of UM3 whileamendments with biochar and vermicompost resulted in 30 reduction in severity in the short rains season of2014 During the long rains of 2014 and the short rain season of 2014 PSI was significantly reduced (p lt 005)in plots amended with biochar and vermicompost or their combinations In LR of 2014 disease severity wasreduced by 39 to 46 while in the SR of 2014 it was reduced by only 20 to 29 Control plots had thehighest PSI in the second week after planting in all three seasons

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 183 of 196

45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013Soil amendments had a significant effect (p lt 005) on the population of fungi isolated from the soils two weeks afterplanting of common bean in the short rain season of 2013 (Table 7) Fusarium spp was the most abundant fungiisolated across all treatments while the lowest populations isolated were those of Macrophomina spp Significantdifferences (p lt 005) were observed in the populations of Fusarium spp with different treatments Control plots hadthe highest populations while plots amended with vermicompost and fertilizer resulted in a 38 reduction

Table 6 Effect of different treatment on bean root rot severity () two weeks after planting in the long and shortrains seasons of 2013 and 2014 in the four AEZs

Treatments Short rains season 2013 Long rains season 2014 Short rains season 2014

LM1 LM2 UM1 UM3 Trt LM1 LM2 UM1 UM3 Trt Mean LM1 LM2 UM1 UM3 Trt Mean

Control 476a 455a 521a 535a 497a 473a 589a 519b 537a 529a 533a 555a 493b 549a 532a

Fertilizer 427ab 350bcd 398bc 442b 404b 448a 422b 580a 483b 483b 474b 500b 580a 457b 503b

Biochar 457a 428a 368cde 396bc 412b 365bc 317d 325c 338c 336c 468b 415c 424c 414bc 430c

Biochar + Fertilizer 329c 317d 427b 404bc 369c 321cd 372c 343c 350c 346c 478b 429c 408c 428bc 436c

Vermicompost 334c 395b 339d 372c 360c 270d 356cd 360c 331c 329c 393c 500b 434c 460b 447c

Vermicompost +

Fertilizer 383bc 361bcd 368cde 382c 374c 371b 345cd 325c 310c 338c 397c 432c 433c 434bc 424c

Biochar +

Vermicompost 348c 323cd 393bcd 395bc 365c 321cd 350cd 316c 317c 326c 405c 453bc 427c 404c 422c

Biochar +

Vermicompost +

Fertilizer 373bc 378bc 319e 400bc 367c 333bcd 339cd 316c 347c 334c 399c 417c 449bc 430bc 424c

LSD Inter 55 48 52

Trt x AEZ

LSD Treatments 27 24 26

CV 275 252 225

Note Means with same letter(s) within the same column are not significantly different at p 005 AEZ ndash Agro-ecologicalzones LM1 ndash lower midland zone 1 LM2 ndash lower midland zone 2 UM1 ndash Upper midland zone 1 UM3 ndash uppermidland zone 3 Trt ndash Treatment LSD Least significant difference at 5 level and CV Coefficient of variation

Mean

Table 7 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks afterplanting common bean in the short rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1341a 463a 353a 330a 29ab 35bc 81bcd 67bc

Fertilizer 1338a 406b 373a 310a 37a 13c 88abcd 113bc

Biochar + Fertilizer 1160b 293c 297b 237b 12b 89a 119a 142ab

Vermicompost 1146b 303c 277b 240b 19ab 44b 90abcd 164ab

Biochar +Vermicompost +Fertilizer 1113b 306c 264b 236b 22ab 31bc 61d 187a

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 184 of 196

Table 7 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Biochar 1101b 315c 263b 231b 20ab 46b 65cd 148ab

Vermicompost +Fertilizer 1099b 287c 262b 247b 23ab 42b 94abc 119bc

Biochar +Vermicompost 1085b 307c 257b 223b 33ab 44b 112ab 113bc

LSD 113 37 45 42 24 22 32 59

CV 391 442 598 630 4341 2041 1433 1757

Fpr lt0001 lt0001 lt0001 lt0001 0329 0016 0004 0004

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndash Aspergillusspp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient of variation

Biochar and vermicompost treatments also resulted in a 30 reduction in the populations of Pythium andRhizoctonia spp when compared to control plots Biochar and fertilizer treatments were observed to result in a60 and 30 increase in populations of Trichoderma and Aspergillus spp respectively when compared tocontrol The highest populations of Penicillium spp were found in plots treated with a combination of biocharvermicompost and fertilizer which was 64 higher than the control which had the lowest populations

46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013Significant differences were observed in the population of fungi isolated from the soil rhizosphere six weeksafter planting during the long rains season of 2013 (Table 8) Fusarium spp populations were found highestacross all treatments while Macrophomina spp was the least isolated The highest population of Fusarium sppwas recorded in control plots whereas biochar and vermicompost amendments caused a 50 reduction in thepopulations of Fusarium spp Biochar treatments resulted in a 54 and 49 reduction in the populations ofRhizoctonia and Pythium spp respectively Control plots also had the highest populations of these fungiBiochar and vermicompost treatments resulted in the highest populations of beneficial fungi including

Table 8 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Control 1542a 499a 318a 380a 19abc 08c 261b 56de

Control + Fertilizer 1528a 443a 356a 359a 31a 05c 263b 37e

Biochar +Vermicompost +Fertilizer 1150a 244b 177c 208bc 21ab 29b 478a 67cde

Biochar + Fertilizer 1148a 244b 183bc 214bc 05bc 17bc 300b 80bcd

Verm + Fertilizer 1145a 289b 228b 240b 08bc 26b 274b 108b

Biochar 1142a 248b 161c 191c 03c 14bc 269b 63de

Biochar +Vermicompost 1083a 241b 203bc 211bc 09bc 31b 246b 97bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 185 of 196

Trichoderma spp and Aspergillus spp whereas plots treated with vermicompost alone had the highestpopulations of Penicillium spp The lowest populations of Trichoderma spp and Aspergillus spp were recordedin fertilizer treated plots with significant differences (p lt 005) when compared to control

47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013Soil amendments were observed to have an effect on root rot pathogens and other soil inhabiting fungi at thetime of bean harvest after the long rains season of 2013 (Table 9) Fusarium spp were highly prevalent among

Table 8 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus Penicilliumcolonies spp spp spp spp spp spp spp

Vermicompost 1057a 249b 178c 205bc 02c 113a 181b 157a

LSD NS 99 45 40 17 18 117 30

CV 507 637 772 624 4210 2274 1625 1434

Fpr 007 0001 lt0001 0001 lt0001 lt0001 lt0001 lt0001

Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp NS No significant difference LSD Least significant difference at 5level and CV Coefficient of variation

Table 9 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of commonbean in the long rains season of 2013

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Trichoderma Aspergillus PenicilliumColonies spp spp spp spp spp spp spp

Control 1613a 636a 151b 428a 36a 100ab 195a 114c

Fertilizer 1205b 443b 196a 365b 30a 117ab 157abc 58d

Biochar 869cd 255c 85c 211c 10bc 25c 137bc 131bc

Biochar +Fertilizer + 757d 235c 59d 206cd 04bc 91abc 183ab 104cdVermicompost 1171b 271c 71d 202cd 002c 135a 184ab 208a

Vermicompost+ Fertilizer 1002bc 237c 107c 218c 001c 139a 131c 134bc

Biochar +Vermicompost 1017bc 254c 91cd 168d 11b 113ab 189a 146bc

Biochar +Vermicompost +Fertilizer 988bcd 206c 74d 196cd 02bc 56bc 205a 178ab

LSD 243 82 32 42 1 69 49 55

CV 439 541 1061 647 3196 2786 1115 1618

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 0016 0018 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 186 of 196

all the fungi across all treatments while Macrophomina spp was the least of all fungi Significant differences(p 005) were found in population of all fungi across the treatments except for Aspergillus spp where nosignificant differences were recorded Treatment combinations of biochar vermicompost and fertilizer resultedin the reduction of Fusarium spp population by 67 when compared to control Vermicompost and fertilizercombination reduced Fusarium by 63 The population of Pythium spp was significantly lower in biochar andfertilizer treatment translating to a 60 population reduction Populations of Rhizoctonia were lowest inbiochar and vermicompost treatment combination while the highest populations were recorded in the non-amended control plots Vermicompost and fertilizer treatment combination at the same time resulted in elevatedpopulation of Trichoderma spp which were lowest in biochar treatment Vermicompost standalone treatmentsresulted in significantly (p lt 005) high populations of Penicillium spp which were lowest in the control plots

48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014

Soil amendments were observed to have a significant effect (p lt 005) on the population of bean root rot twoweeks after planting in 2014 (Table 10) Fusarium spp were most abundant across all treatments while thelowest populations were of Macrophomina spp Populations of Fusarium spp were significantly different(p lt 005) across the six treatments The highest populations were found in the control plots while soilsamended with vermicompost had a 59 reduction in populations Vermicompost treatment resulted in a 52reduction of Pythium spp populations Combination of vermicompost and fertilizer reduced R solanipopulations by 48 Biochar treatments were observed to reduce all root rot pathogens by 40 margin Thecontrol plots recorded the highest populations of all root rot pathogens Consequently the populations ofPenicillium Aspergillus Paecilomyces Athrobotrys and Trichoderma spp were highest in vermicompost treatmentsin the range of 60 to 90 Biochar resulted in an increase of between 50 and 80 of these fungi Similarobservations were made in the short rains season of 2014 though the effect of the treatments was observed tohave reduced by a margin of 20 (Table 11)

Table 10 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after

planting common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1402a 529a 384 317a 45a 08d 36d 38bc 03c 41e

Fertilizer 1325a 459b 379 346a 33ab 16d 24d 13d 03c 53de

Biochar 953bc 311c 185 194b 05d 56bc 95ab 19cd 04c 84ab

Biochar + Fertilizer 977bc 267de 221 189b 10cd 72ab 76bc 44ab 23b 77bc

Vermicompost 1048b 214f 183 189b 17bcd 100a 119a 67a 57a 103a

Vermicompost + Fert 910c 225f 193 164b 21bcd 95a 51cd 49ab 56a 57c

Biochar +Verm 952bc 272d 185 197b 33ab 38cd 76bc 56ab 30b 64bcd

Biochar + Verm + Fert 902c 233ef 191 177b 23bc 62bc 67bc 56ab 47a 46d

LSD 102 37 NS 38 17 32 28 24 14 20

CV 378 486 643 679 2616 1807 1453 2393 2002 1464

Fpr lt0001 lt0001 0074 lt0001 005 005 lt0001 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 187 of 196

Table 11 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) two weeks after planting

of common bean during short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1391a 520a 367a 289ab 13ab 47bc 54bc 49cde 001d 51d

Fertilizer 1305ab 467b 390a 323a 33a 19c 28c 21e 04cd 19e

Biochar 1299ab 392c 311b 246bc 18ab 74ab 66b 30de 17bc 146a

Biochar + Fertilizer 1224bc 382c 293bc 254bc 08b 48bc 55bc 63bc 29b 92b

Vermicompost 1305ab 352cd 288bc 258bc 13ab 92a 118a 56cd 44a 85bc

Vermicompost + Fert 1157c 321d 252c 239c 18ab 89ab 68b 112a 001d 57d

Biochar + Verm 1217bc 373c 273bc 258bc 10ab 77ab 80b 62bc 21b 64cd

Biochar + Verm + Fert 1227bc 348cd 290bc 246bc 07b 69ab 73b 92ab 04cd 98b

LSD 117 47 41 46 23 43 35 31 14 26

CV 371 490 539 676 4674 2023 1856 2143 3671 1539

Fpr lt0001 lt0001 0002 lt0001 lt0001 005 lt0001 0004 0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp Fert Fertilizer Verm Vermicompost LSD Least significantdifference at 5 level and CV Coefficient of variation

49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014

Significant differences were observed in the population of root rot fungi isolated from the soils of treated plotssix weeks after planting in the long rains season of 2014 (Table 12) Fusarium spp was the most prevalent of allthe fungi across all treatments while Macrophomina spp was the least Vermicompost treatment and thecombinations of biochar and fertilizer were observed to cause a 40 to 50 reduction in the populations ofFusarium spp when compared to control Biochar and fertilizer amendments also resulted in a 32 reductionof Pythium populations and a 42 reduction of Rhizoctonia populations Control plots had the highestpopulations of all the root rot fungi Vermicompost treated plots were observed to have the highest populationof Penicillium spp representing a 55 difference from the control plots which had the lowest populationsPaecilomyces spp Trichoderma spp and Aspergillus spp were positively affected by biochar treatments Athrobotrysspp population was highest in plots treated with a combination of biochar vermicompost and fertilizerwhereas the control plots had the lowest population

Similar trends in reduction of root rot populations were observed in the short rains season of 2014but at lower percentages (Table 13) Significant differences (p lt 005) were observed for all root rot fungiVermicompost treatments resulted in a reduction of between 32 and 37 for Fusarium Pythium and Rhizoctoniaspp while control plots recorded the highest population of the root rot fungi Treatment combinationof biochar vermicompost and fertilizer resulted in 50 and 89 increase in the populations of Paeciliomycesspp and Athrobotrys spp Biochar and fertilizer on the other hand resulted in a 54 increase in the populationsof Aspergillus spp with the control plots recording the lowest populations of Aspergillus and Athrobotrys spp

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 188 of 196

Table 12 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks after planting

common bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1582a 504a 297a 320a 63abc 68c 153c 78a 18c 81ab

Fertilizer 1523a 462a 303a 276a 82a 84bc 171bc 80a 26c 38c

Biochar 1339b 285b 204b 198b 38c 86bc 225b 105a 95a 102a

Biochar + Fertilizer 1327bc 276b 202b 184b 67abc 107bc 295a 86a 41bc 68b

Vermicompost 1329bc 294b 215b 177b 52bc 197a 192bc 102a 41bc 59bc

Vermicompost +

Fertilizer 1219c 256b 229b 203b 42c 116b 192bc 90a 25c 66b

Biochar +

Vermicompost 1264bc 304b 209b 193b 74ab 109bc 169bc 109a 58b 38c

Biochar +

Vermicompost +

Fertilizer 1299bc 293b 203b 217b 41c 95bc 181bc 91a 115a 63b

LSD 118 52 43 46 29 42 60 45 28 23

CV 347 622 714 809 1909 1631 1238 1911 2384 1565

Fpr lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 lt0001 007 0009 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 Nonpathogenic fungi ndashAspergillus spp Penicillium spp Trichoderma spp LSD Least significant difference at 5 level and CV Coefficient ofvariation

Table 13 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) six weeks

after planting common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1609a 500a 339a 366a 52a 97b 155b 51bc 05c 56ab

Fertilizer 1554ab 448b 307a 337a 59a 56c 197b 85ab 27abc 36bc

Biochar 1387cde 377c 261b 274b 47a 74bc 199b 96a 21bc 38bc

Biochar + Fertilizer 1468bc 361c 262b 277b 62a 70bc 329a 47bc 28abc 33c

Vermicompost 1345de 333c 258b 228c 69a 136a 192b 50bc 37ab 41bc

Vermicompost +Fertilizer 1277e 343c 229b 276b 51a 81bc 185b 39c 20bc 52bc

Biochar +Vermicompost 1431cd 350c 265b 285b 47a 91bc 178b 99a 43ab 74a

Biochar +Vermicompost +Fertilizer 1375cde 338c 250b 290b 36a 103ab 170b 102a 48a 39bc

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 189 of 196

Table 14 Effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest of common

bean in the long rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1595ab 506a 253a 341b 75b 89b 175 90ab 17e 48c

Fertilizer 1648a 478a 275a 391a 110a 89b 175 67b 21e 43c

Biochar 1467c 310b 165b 217cd 47c 142a 258 88b 132a 108ab

Biochar + Fertilizer 1477bc 312b 177b 195d 47c 160a 304 95ab 67c 121a

Vermicompost 1322d 307b 185b 212cd 49bc 136ab 210 77b 57cd 90b

Vermicompost +

Fertilizer 1399cd 325b 175b 250c 53bc 123ab 265 87b 34de 86b

Biochar +

Vermicompost 1361cd 312b 174b 200d 75b 125ab 183 128a 70bc 94ab

Biochar +

Vermicompost +

Fertilizer 1394cd 284b 184b 229cd 40c 131ab 236 82b 96b 112ab

LSD 124 52 32 46 27 47 NS 38 28 27

CV 341 583 656 713 1716 1520 1071 1736 1939 1249

Fpr lt0001 0001 lt0001 lt0001 lt0001 lt0001 0065 lt0001 lt0001 lt0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014During the harvest period of long rains season of 2014 soil amendments were observed to have an effect onroot rot pathogens and other soil inhabiting fungi (Table 14) Fusarium spp was most isolated of all the fungiin all treatments while Macrophomina spp was the least isolated Significant differences (p 005) were observedin population of all fungi across the treatments Treatment combination of biochar vermicompost and fertilizerresulted in the reduction of Fusarium spp population by 39 and the highest populations being recorded incontrol plots The population of Pythium spp was significantly lower (p lt 005) in biochar and fertilizertreatment translating to a 40 reduction in population Rhizoctonia was also observed to be lowest in biocharand fertilizer treatment combinations while the highest populations were recorded in the control plots Biochar

Table 13 (Cont)

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

LSD 113 49 37 42 NS 38 66 42 23 21

CV 3 1 511 543 582 2138 1644 1269 2302 3349 1613

Fpr lt0001 lt0001 lt0001 lt0001 010 lt0001 001 0016 0003 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 LSD Least significantdifference at 5 level CV Coefficient of variation and NS- No significant difference

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 190 of 196

and fertilizer treatment combination at the same time resulted in elevated population of Penicillium sppAspergillus spp and Trichoderma spp The population of these three genera was observed to be lowest in thecontrol plots Similar trends were observed for root rot pathogen as well as other soil inhabiting fungi in theshort rains season of 2014 though the percentage reduction in populations was 10 lower than in the longrains season (Table 15)

Table 15 The residual effect of biochar and vermicompost on fungal populations (times 103 CFUg soil) at harvest

of common bean in the short rains season of 2014

Treatments Fungal Fusarium Pythium Rhizoctonia Macrophomina Penicillium Aspergillus Paecilomyces Athrobotrys Trichoderma

Colonies spp spp spp spp spp spp spp spp spp

Control 1555a 498a 278a 380a 42a 69cd 167b 51bcd 09c 55bc

Fertilizer 1415b 439b 250abc 297b 45a 60d 189b 85a 28bc 36c

Biochar 1374b 378c 199c 258bcd 65a 58d 203b 87a 58a 75ab

Biochar + Fertilizer 1375b 371c 219bc 226d 66a 90bcd 304a 33cd 17bc 45c

Vermicompost 1340b 364c 222bc 227d 53a 157a 188b 58abcd 31b 38c

Vermicompost +

Fertilizer 1319b 361c 253ab 231cd 59a 121ab 181b 27d 23bc 77ab

Biochar +

Vermicompost 1410b 351c 232bc 247cd 63a 104bc 197b 80ab 25bc 90a

Biochar +

Vermicompost +

Fertilizer 1348b 346c 228bc 268bc 46a 80bcd 183b 66abc 36b 92a

LSD 112 49 34 40 NS 41 64 33 19 27

CV 319 504 573 591 2083 1789 1272 1885 2729 1338

Fpr lt0001 lt0001 lt0001 lt0001 009 lt0001 0006 0018 lt0001 0001

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean

Bean grain yield was significantly affected (p 005) by the treatments in all the seasons except the short rainsseason of 2014 where the differences were not significant (Table 16) The long rains season of 2013 recordedthe highest average yield across all treatments The yields were observed to be 17 higher than the long rainsseason of 2014 which ranked second There was however a significant drop of 45 in yield from the long rainsseason of 2013 into the short rains season of the same year This trend was reversed in the long rains season of2014 recording a 30 to 50 increase in yield across all treatments

Vermicompost and fertilizer treatments had the highest grain yield in the long rains and short rains of 2013as well as in the long rains of 2014 In the long rains of 2013 the yield was observed to be 81 higher invermicompost and fertilizer treatment and 46 higher in biochar vermicompost and fertilizer treatment plotsThese were in comparison to the non-amended control plots During the short rains of 2013 plots that wereamended with solitary biochar treatments recorded the lowest grain yield as was the case during the longrains of 2013 There was no significant difference in bean yield in the short rains season of 2014 where theyields were greatly reduced Treatment combinations of vermicompost and fertilizer still recorded the highestgrain yield while biochar and vermicompost plots had the lowest yield

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 191 of 196

Bean seed weight was affected by the soil amendment treatments in all the seasons with differences beingsignificant (p 005) in all the seasons (Table 16) Vermicompost and fertilizer amended treatment plots hadthe highest 100 seed weight in three seasons averaging 8 to 20 change in g100 seeds Biochar vermicompostand fertilizer amended treatment plots had the second highest seed quality which was 10 higher than thecontrol plots in the long rains of 2013 In the subsequent short rain season of 2013 biochar treated plotsrecorded the lowest seed quality though it was observed to only be significantly different (p lt 005) from thevermicompost and fertilizer treated plots from which the highest seed quality was recorded In the short rainsseason of 2014 the highest seed quality was in biochar and fertilizer treatment combinations This was 48higher than in vermicompost amended treatment plots which had the lowest seed quality the differences beingsignificant (p 005)

5 Discussion

51 Effect of soil amendments on plant emergencePlant emergence was affected by the application of individual treatments of biochar and vermicompost as wellas their combinations Soil amendments positively influenced the plant emergence Treatment combinationsof biochar and vermicompost had the highest emergence immediately after application and the subsequentseason when amendments were not applied The results concur with those reported by Ievinsh et al (2017) andArancon et al (2012) where there was increase in germination of hemp seeds and cucumber seeds treated withvermicompost Solaiman et al (2011) also reported an increase in mung bean germination with biochar treatmentThe results from this study also confirm the presence of positive residual effect of biochar and vermicompost

Table 16 Effect of biochar and vermicompost on common bean yields (kgha) and seed quality (weight per

100 seeds) across all the four seasons in 2013 and 2014

Treatments Common bean grain yield (kgha) Common bean seed quality (g100 seeds)

Long Short Long Short Long Short Long Shortrains rains rains rains rains rains rains rains2013 2013 2014 2014 2013 2013 2014 2014

Vermicompost +Fertilizer 5652a 3063a 4811a 647a 333a 321a 373a 175b

Biochar +Vermicompost +Fertilizer 4897ab 2823ab 4459ab 468a 321a 292a 363a 179b

Vermicompost 4550abc 2526ab 3335bc 486a 319a 295a 361a 145c

Biochar + Fertilizer 4338bcd 2540ab 3809abc 510a 327a 282a 365a 214a

Biochar +Vermicompost 4133bcd 2207b 4565ab 411a 319a 294a 363a 164bc

Control + Fertilizer 3777bcd 239abc 3195c 572a 306a 285a 362a 168bc

Biochar 3539cd 1728c 2591c 528a 304a 262a 361a 169bc

Control 3117d 2715ab 3505bc 443a 297a 282a 348a 191ab

LSD 1260 769 1243 NS NS NS NS 28

CV 541 624 717 117 142 347 123 284

Fpr 0004 0037 0005 088 0065 0524 0532 0002

Note Means with same letter(s) within the same column are not significantly different at p 005 NS No significantdifference LSD Least significant difference at 5 level and CV Coefficient of variation

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 192 of 196

on plant emergence in short rain seasons of 2013 and 2014 which has not been previously reported Plantemergence was also observed to be influenced by the AEZs Lower midland humid (LM1) and upper midlandhumid (UM1) were observed to have higher emergence in the long rains season of 2014 and the two short rainseasons However in the long rains season of 2013 UM3 and LM2 were observed to have significantly higheremergence This can be attributed to the distribution of the rainfall at the time of planting Upper midland zone3 (Kakamega region) recorded highest precipitation at 712 mm in the three growing months and lowest in LM1(N Teso sub county) at 447 mm for the three months of growth Plant emergence is of great importance since theplant population would eventually affect the final yield

52 Effect of soil amendments on root rot disease incidenceDifferent treatments of biochar and vermicompost and their interaction with AEZrsquos reduced bean root rotincidence The findings also point to the influence of AEZrsquos on the effectiveness of soil amendments insuppressing root rot disease in common bean Disease incidence was reduced by 60 in both the long rainseasons when the treatments were applied and 40 in the short rain seasons with no treatment applicationbut with residual effect Treatment combinations of biochar and vermicompost greatly reduced root rot incidenceafter application These plots had the lowest disease incidence showing a synergy at play while those thatreceived one amendment alone had a higher disease incidence which was however significantly (p lt 005)lower than the control plots This finding corroborate previous findings by Chaoui et al (2002) and Edwardsand Arancon (2004b) who reported on suppression of root rots in strawberry using vermicompost Jaiswalet al (2014) also reported on root rot disease suppression in cucumber using biochar

During the period of this research rainfall amounts varied between 143 mm and 712 mm in the fourdifferent seasons in the months of March to July September to November of 2013 and 2014 Disease incidencewas lower in the long rains season after application of soil amendments This was observed both at two weeksand six weeks after planting where the disease incidence was reduced by as much as 60 as compared to thatin the control plots In the long rains season the highest incidence was in LM1 while UM3 recorded the lowestThis concurs with previous studies by Mwangrsquoombe et al (2007) and Hall and Philips (1992) who worked onbean root rots in Embu Kenya and South Western Uganda respectively They observed that elevated rainfallstimulated root infection In turn this would lead to accumulation of inoculum in the root tissues The impactof the inoculum build up is then felt in the short rains season with elevated root rot incidences where norotation is practiced However in this study findings show that amendments with biochar and vermicompostprevented development of inoculum resulting to reduced disease incidence Similar findings have been reportedby Warnock et al (2007) and Ameloot et al (2013) that biochar can be used as a source of energy or mineralnutrients which may induce changes in community composition

In the subsequent season disease incidence was observed to be higher in the plots where no inorganicfertilizer sympalreg (NPK 02315) had been applied This implies the importance of the phosphorus in rootdevelopment and in turn disease suppression Similar findings were reported Yamato et al (2006) who statedthat biochars antifungal potential was due to its important properties among them increased nutrient retentionincreased soil cation exchange capacity and effects on Phosphorus Ceroz and Fitzsimmons (2016) and Cichyet al (2007) observed that disease severity may reduce through new growth resulting from improved crop vigoras a result of phosphorus nutrition

53 Effect of soil amendments on root rot disease severity in Western KenyaRoot rot disease severity was greatly reduced by as much as 60 following application of biochar andvermicompost soil amendments across all seasons and growth stages In the subsequent seasons when noamendments were applied disease severity was reduced by 30 Treatment combinations of biochar andvermicompost with addition of sympalreg fertilizer had the lowest disease severity than with amendmentsalone Similar findings were reported by Matsubara et al (2002) who observed reduced Fusarium wilt diseasein Asparagus following application of biochar Jaiswal et al (2014) also reported reduction in damping offdisease caused by Rhizoctonia solani in cucumber and beans following addition of 05 wtwt of greenhousewaste biochar Other findings by Jack (2012) also showed disease suppression in cucumber caused by Pythiumaphanidermatum following application of vermicompost extract

The control plots recorded the highest severity in all seasons across the AEZrsquos This can be attributed to thecontinuous planting of beans with no rotation period Disease severity did not however vary greatly across the

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 193 of 196

agro-ecological zones though LM2 appeared to have the highest severity while the lowest severity was recordedin UM1 These levels of severity can also be linked to the rainfall received in different agro-ecological zonesSimilar findings have been reported by Mwangrsquoombe et al (2007) working on bean root rots in Embu Theyobserved that increased rainfall leads to high soil moisture which favors root rot pathogens such as species ofPythium and Rhizoctonia

54 Effect of soil amendments on fungal populations isolated from soils planted with common beanTreatments with biochar vermicompost and in combination were found to greatly impact soil fungal populationsVermicompost treatment resulted in significant (p lt 005) reduction of Pythium spp populations across theagro-ecological zones Vermicompost treatments also resulted in the highest reduction of Fusarium spppopulations at the second week of plant growth With the progression of the cropping season biochar treatmentsas well as in combination with vermicompost resulted in significant reduction of Fusarium spp and Rhizoctoniaspp These findings are similar to those of Jack (2012) and Scheuerell et al (2005) who observed significantsuppression of P aphanidermatum and P ultimum populations in soils treated with vermicompost in cucumberand beans respectively Graber et al (2010) attributed the reduction of detrimental fungal populations tochemical compounds in the residual tars found on biochar They identified several biochar compounds knownto have detrimental effects on growth and survival of pathogenic microorganisms In low levels these compoundscan suppress sensitive components of the soil microorganisms and result in a proliferation of resistant microbialcommunities that are beneficial to plant growth This phenomenon was observed in biochar treatments whichresulted to an increase in population of beneficial microorganisms such as Trichoderma spp Paeciliomyces sppand Athrobotrys spp Similarly vermicompost treatments were also observed to result in an increase of Penicilliumspp and Aspergillus spp after application and also as a residual effect when no amendments were applied

55 Effect of biochar and vermicompost on yield and seed weight of common beanYields of common bean were significantly (p 005) influenced by the treatments in all the seasons other thanthe short rains season of 2014 where the differences were not significant Higher grain yield was recorded inplots amended with vermicompost and sympalreg fertilizer treatments as well as in the biochar vermicompostand fertilizer amended plots The amendments resulted in yield increase of between 46 and 81 Similarfindings have also been reported in previous studies by Guerena et al (2015) and Lin et al (2015) Theyobserved an increase in bean biomass and grain yield following the application of biochar and vermicompostThis study also showed an increase in yield when biochar was combined with fertilizer than in individualapplication of biochar or Sympal fertilizer Similar results were reported earlier by Liang et al (2014) and Oramet al (2014) who reported improved yield following application of biochar and organicinorganic fertilizerstogether This was attributed to an increase in nutrient resource to plants Liard et al (2010) on the other handdemonstrated heightened nutrient preservation in soils amended with biochar This explains why biocharstand-alone treatments posted low yields which were only higher than the control treatments without inorganicfertilizer in the first season and lowest in the subsequent seasons Seed weight was highest in vermicompostand fertilizer amended treatment plots ranging between 333g and 373g 100-1 seeds followed by biochar andfertilizer amended treatment plots ranging between 3265 and 3649g 100-1 seed Biochar standalone treatmentplots recorded low 100 seed weight in subsequent seasons when no amendments were added The non-amended control treatment plots recorded the lowest seed weight of 297g 100-1 seeds

6 ConclusionApplications of biochar and vermicompost greatly inhibited the growth of root rot fungi hence protecting theplants from pathogenic attack The soil amendments do have the potential to suppress soil borne pathogenicmicroorganisms directly and also induce multiplication of resistant microbial communities that are beneficialto plant growth They also suppress pathogens in the soil environment The addition of amendments as acombination or standalone treatments resulted in reduction of incidence and severity of root rot This in turnled to increased common bean productivity

Conflicts of interestAuthors declare no conflict of interests

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

Da Silva Botelho L Barrocas EN Da Cruz Machado J and De Saacute Martins R (2015) Detection of Sclerotiniasclerotiorum in soybean seeds by conventional and quantitative PCR techniques Journal of Seed Science37(1) 55-62

Dick MW (1990) Key to Pythium College of Estate Management Whiteknights Reading England p 64

Edwards CA and Arancon NQ (2004b) Vermicomposts suppress plant pest and disease attacks Biocycle45(3) 51-55

Elad Y Rav David D Meller Harel Y Borenshtein M Ben Kalifa H Silber A and Graber ER (2010)Induction of systemic resistance in plants by biochar a soil-applied carbon sequestering agentPhytopathology 9 913-921

Fischer D and Glaser B (2012) Synergisms between compost and biochar for sustainable soil ameliorationIn Kumar S (ed) Management of Organic Waste In Tech Rijeka and Shanghai 167-198 httpsdoiorg10577231200

Samuel Were et al AfrJBioSc 3(1) (2021) 176-196 Page 194 of 196

AcknowledgmentWe are grateful to USDA-NIFA FEED THE FUTURE project which is the US Governmentrsquos Global Hunger andFood Security Initiative for their support and funding of the study We also acknowledge Cornell UniversityInternational Institute of Tropical Agriculture for their support

ReferencesAbawi GS Ludwig JW and Gugino BK (2006) Bean root rot evaluation protocols currently used in New

York Annu Rep Bean Improv Cooperative 49 83-84

Abawi GS and Pastor-Corrales MA (1990) Root rots of beans in Latin America and Africa DiagnosisResearch Methodologies and Management Strategies CIAT Publication No 35 Cali Colombia 114 pp

Agegnehu G Bird M Nelson P and Bass A (2015) The ameliorating effects of biochar and compost on soilquality and plant growth on a Ferralsol Soil Resource 53 1-12

Agrios GN (2005) Plant Pathology 5th edition Elsevier Academic Press San Diego California 384 pp

Ameloot N Graber E R Verheijen F G and De Neve S (2013) Interactions between biochar stability andsoil organisms review and research needs European Journal of Soil Science 64(4) 379-390

Arancon NQ Pant A Radovich T Hue NV Potter JK and Converse CE (2012) Seed germination andseedling growth of tomato and lettuce as affected by vermicompost water extracts (Teas) HortScience 471722-1728

Assefa S Seid A Chemeda F and Sakhuja PK (2014) Evaluation of green manure amendments for themanagement of fusarium basal rot (Fusarium oxysporum fsp cepae) on shallot International Journal ofAgronomy 2014 1-6 doi 1011552014150235

Bailey K and Lazarovits G (2003) Suppressing soil-borne diseases with biomass management and organicamendments Soil and Tillage Research 72 169-180

Bonanomi G Gaglione SA Cesarano G Sarker TC Pascale M Scala F and Zoina A (2017) Frequentapplications of organic matter to agricultural soil increase fungistasis Pedosphere 27 86-95

Buruchara RA Rubyogo JC Sperling L and Muthoni R (2001) A case study on developing anddisseminating integrated pest management technologies for bean root rots in eastern and central AfricaPaper presented at the Global Forum on Agricultural Research 21-23 May 2001 Dresden Germany423

Chaoui H Edwards CA Brickner A Lee SS Arancon NQ (2002) Suppression of the plant diseasesPythium (damping-off) Rhizoctonia (root rot) and Verticillium (wilt) by vermicomposts Proceedings ofBrighton Crop Protection Conference- Pest and Diseases II 8B- 3 711-716

Cichy KA Snapp SS Kirk WW (2007) Fusarium root rot incidence and root system architecture in graftedcommon bean lines Plant Soil 300 233-244

Cerozi BDS and Fitzsimmons K (2016) The effect of pH on phosphorus availability and speciation in anaquaponics nutrient solution Bio-resource Technology 219778-781 doi 101016jbiortech201608079Epub 2016 Aug 24 PMID 27575336

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Cite this article as Samuel A Were Rama Narla E W Mutitu JW Muthomi Liza M Munyua DriesRoobroeck Bernard Vanlauwe and Janice E (2021) Biochar and vermicompost soil amendments reduceroot rot disease of common bean (Phaseolous Vulgaris L) African Journal of Biological Sciences 3(1) 176-196doi 1033472AFJBS312021176-196

• Title and Authors
• Abstract
• 1 Introduction
• 2 Materials and methods
• • 21 Production of soil amendments biochar and vermicompost
  • 22 Study site and experimental layout
  • 23 Assessment for root rot disease incidence and severity
  • 24 Isolation of root rot fungal pathogens from infected bean roots and rhizosphere soil
  • 25 Effect of biochar and vermicompost on yield of common bean
  • • 3 Data collection and analysis
    • 4 Results
    • • 41 Physical and chemical characteristics of biochar and vermicompost
      • 42 Effect of soil amendments on plant emergence
      • 43 Effect of soil amendments on incidence of root rot in Western Kenya
      • 44 Effect of soil amendments on bean root rot severity in Western Kenya
      • 45 Effect of soil amendments on populations of root rot fungal pathogens two weeks after planting commonbean in 2013
      • 46 Effect of soil amendments on population of root rot fungal pathogens six weeks after planting common beanin 2013
      • 47 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rains of 2013
      • 48 Effect of soil amendments on population of root rot fungal pathogens two weeks after planting of commonbean in the long rain season of 2014
      • 49 Effect of soil amendments on populations of root rot fungal pathogens six weeks after planting commonbean during the long rain season of 2014
      • 410 Effect of soil amendments on population of root rot fungal pathogens at harvest of common bean during thelong rain season of 2014
      • 411 Effect of biochar and vermicompost on yield and 100 seed weight of common bean
      • • 5 Discussion
        • • 51 Effect of soil amendments on plant emergence
          • 52 Effect of soil amendments on root rot disease incidence
          • 53 Effect of soil amendments on root rot disease severity in Western Kenya
          • 54 Effect of soil amendments on fungal populations isolated from soils planted with common bean
          • 55 Effect of biochar and vermicompost on yield and seed weight of common bean
          • • 6 Conclusion
            • Conflicts of interest
            • Acknowledgment
            • References
            • Cite this article as