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EVALUATION OF ROW SPACING AND MULCHING ON WEED CONTROL,
GROWTH AND YIELD OF GREEN PEPPER IN BUSIA COUNTY, KENYA
By
OCHARO EDGAR
A144/CE/23290/2013
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN
AGRONOMY IN THE SCHOOL OF AGRICULTURE AND ENTERPRISE
DEVELOPMENT OF KENYATTA UNIVERSITY
JUNE 2018
ii
DECLARATION
This thesis is my original work and has not presented for a degree or any other award in
any University.
Edgar N. Ocharo
Sign ------------------------------------- Date ----------------------------------------
University Supervisors
We confirm that the work reported in this thesis was carried out by the candidate under our
supervision and has been submitted with our approval as university supervisors.
Dr. Nicholas Korir Kibet
Department of Agricultural Science and Technology, Kenyatta University
Sign ------------------------------------- Date ----------------------------------------
Dr. Joseph Onyango Gweyi
Department of Agricultural Science and Technology, Kenyatta University
Sign ------------------------------------- Date ----------------------------------------
iii
DEDICATION
I would like to dedicate this thesis to my Father, Late Mother, Wife and all other family
members whose consistent encouragement and support has significantly contributed to
successful completion of my graduate work.
I also dedicate this work to my lovely daughter, who always reminded me to work hard
and eager that she’ll be able to see my success.
iv
ACKNOWLEDGEMENTS
The academic program that culminated into this thesis and the completion thereof would
not have been possible without the assistance from a number of people whom I would love
to express my gratitude to.
First, my gratitude goes to God The almighty who guided me throughout this program and
through processes and challenges of life that came along with this program. With God,
everything is possible. I thank Kenyatta University for granting me an opportunity to be
one of their graduate students. Many thanks to my supervisors, Dr. Nicholas Korir and Dr.
Joseph Onyango Gweyi who read my numerous drafts and for their unconditional support,
patience, valuable and positive contribution to this work. Without their tireless support and
guidance throughout, this study would have been impossible.
I wish to profusely thank my family, for the encouragement and support when it seemed
very tough to continue. Finally, special thanks to my friends and colleagues for their
academic advice and words of encouragement.
v
TABLE OF CONTENTS
DECLARATION........................................................................................................................ ii
DEDICATION .......................................................................................................................... iii
ACKNOWLEDGEMENTS ....................................................................................................... iv
TABLE OF CONTENTS............................................................................................................ v
LIST OF TABLES .................................................................................................................. viii
LIST OF FIGURES ................................................................................................................... ix
ACRONYMS AND ABBREVIATIONS ................................................................................... xi
ABSTRACT ............................................................................................................................. xii
CHAPTER ONE: INTRODUCTION ......................................................................................... 1
1.1 Background study ............................................................................................................. 1
1.2 Problem Statement ............................................................................................................ 3
1.3 Research objectives ........................................................................................................... 4
1.3.1 General objective .................................................................................................. 4
1.3.2 Specific objectives................................................................................................. 4
1.4 Research hypotheses ......................................................................................................... 4
1.5 Significance of the study ................................................................................................... 5
1.6 Conceptual framework ...................................................................................................... 5
CHAPTER TWO: LITERATURE REVIEW .............................................................................. 7
2.1 Origin of green pepper ...................................................................................................... 7
2.2 Agronomic practices for green pepper production ............................................................. 7
2.2.1 Climatic requirements ................................................................................................. 7
2.2.3 Fertilizer requirements ................................................................................................ 9
2.2.4 Green pepper cultivars .............................................................................................. 10
2.3 Importance of green pepper ............................................................................................. 11
vi
2.3.1 Green Pepper Production in Kenya ........................................................................... 12
2.4 Effect of row spacing in green pepper production ............................................................ 13
2.5 Effect of mulching materials on growth and yield of crops .............................................. 19
2.6 Importance of mulching in weed suppression and control ................................................ 23
2.7 Influence of the integration of row spacing and mulching on crop production.................. 25
CHAPTER THREE: MATERIALS AND METHODS ............................................................. 27
3.1 Description of study area ................................................................................................. 27
3.2 Experimental design and treatments ................................................................................ 28
3.3 Source of planting materials, nursery management and transplanting .............................. 29
3.4 Data Collection ............................................................................................................... 30
3.4.1 Growth parameters.................................................................................................... 30
3.4.2 Weed parameters ...................................................................................................... 31
3.4.3 Yield Parameters....................................................................................................... 31
3.5 Data analysis ................................................................................................................... 33
CHAPTER FOUR: RESULTS AND DISCUSSION................................................................. 34
4.1 Effectiveness of row spacing in control of weeds in green pepper .................................... 34
4.1.1 Number of weed species ........................................................................................... 34
4.1.2 Weed vigor ............................................................................................................... 36
4.1.3 Fresh weed biomass .................................................................................................. 37
4.1.4 Weed dry biomass .................................................................................................... 38
4.2 Influence of row spacing on growth and yield of green pepper ........................................ 40
4.2.1 Plant height ............................................................................................................... 40
4.2.2 Number of leaves ...................................................................................................... 41
4.2.3 Number of branches per plant ................................................................................... 43
4.2.4 Fruit mass ................................................................................................................. 44
vii
4.2.5 Fruit length and breadth ............................................................................................ 46
4.2.6 Number of fruits per plant ......................................................................................... 47
4.3 Effect of mulching materials on weed control in green pepper ......................................... 48
4.3.1 Number of weed species ........................................................................................... 48
4.3.2 Weed vigor ............................................................................................................... 49
4.3.3 Fresh weed biomass .................................................................................................. 51
4.3.4 Dry weed biomass .................................................................................................... 52
4.4 Effect of mulching materials on growth and yield of green pepper................................... 53
4.4.1 Seedling vigor ........................................................................................................... 53
4.4.2 Plant height ............................................................................................................... 54
4.4.3 Number of leaves ...................................................................................................... 55
4.4.4 Number of branches .................................................................................................. 56
4.4.6 Stem girth ................................................................................................................. 57
4.4.7 Fruit mass ................................................................................................................. 59
4.4.8 Number of seeds per fruit .......................................................................................... 60
4.4.9 Fruit length and breadth ............................................................................................ 61
4.4. Correlation Analysis for variables .................................................................................. 63
CHAPER FIVE: CONCLUSION AND RECOMMENDATIONS ............................................ 66
5.0 CONCLUSION ............................................................................................................... 66
5.1 RECOMMENDATIONS ................................................................................................ 67
6.0 REFERENCES ................................................................................................................... 68
7.0 APPENDICES .................................................................................................................... 82
viii
LIST OF TABLES
Table 4.1Fresh weed biomass per quadrat (m2) during the long and short rainy seasons of
2015 at Alupe under different plant spacing (cm) at 4, 6 and 8 WAT (Weeks after
transplanting) .................................................................................................................. 38
Table 4.2 Dry weed biomass (g) per quadrat during the long and short rainy seasons of
2015 at Alupe under different plant spacing (cm) at 4, 6 and 8 WAT (Weeks after
transplanting) .................................................................................................................. 39
Table 4.3 Fruit length, fruit breadth and number of fruits per plant during the long and
short rainy seasons at Alupe under different plant spacings (cm) in 2015 ......................... 47
Table 4.4 Mulching materials influence on the weed vigor during the long rains of March
– August and short rains of September - December 2015 at Busia .................................... 50
ix
LIST OF FIGURES
Figure 2.1Conceptual Framework ..................................................................................... 6
Figure 2.1 Green pepper varieties: A-Maxibell; B-Admiral F1; C-Buffalo F1; D-California
Wonder; E-Yolo Wonder and F-Orange Pepper ............................................................... 10
Figure 2.2 Capsicums production in Kenya for period 2006-2010 (HCDA, 2010) ........... 13
Figure 3.1 The study site in Alupe Crops Research Station in Busia County ................... 28
Figure 4.1 Number of weed species per unit quadrat (m2) during the long and short rainy
seasons of 2015 at Alupe at 4 WAT (WAT-Weeks after transplanting). Row spacing is in
cm. .................................................................................................................................. 35
Figure 4.2 Weed vigor of green pepper during the long and short seasons at Alupe in 2015
at 4 WAT (Weeks after Transplanting) ............................................................................ 37
Figure 4.3 Plant height of green pepper during the long and short seasons at Alupe in 2015
at 2, 4, 6 and 8 WAT (Weeks after Transplanting) under different row spacing treatments
(cm) ................................................................................................................................. 40
Figure 4.4 Average number of leaves per plant during the long (a) and short rainy (b)
seasons of 2015 at Alupe under different plant spacing treatments (cm) at 4, 8 and 12 WAT
(Weeks after transplanting) .............................................................................................. 42
Figure 4.5 Influence of plant spacing (cm) on the number of branches per plant during the
long and short rainy seasons of 2015 at Alupe at 4, 6, 8, 10 and 12 WAT (WAT-Weeks
after transplanting ............................................................................................................ 44
Figure 4.6 Average yield per plant (g) of green pepper at different row spacing (cm)
during the long and short rainy seasons at Alupe in 2015 ................................................. 45
Figure 4.7 Number of weed species m2 during the long rain season of March – August (a)
and short rain season of September - December (b) at Busia in 2015 as influenced by
different mulching materials ............................................................................................ 48
Figure 4.8 Aboveground fresh weed biomass (m2) during the long raining season of
March – August and short raining season of September - December 2015 at Alupe under
different mulching materials ............................................................................................ 51
Figure 4.9 Aboveground dry weed biomass during the long rains of March - August and
short raining season of September – December 2015 at Alupe under different mulching
materials .......................................................................................................................... 52
x
Figure 4.10 Influence of mulching materials on seedling vigor of green pepper during the
short rain season of September – December 2015 (A) and long rain season of March –
August 2015 (B) at Alupe, Busia ..................................................................................... 54
Figure 4.11 Influence of mulching materials on the plant height of capsicum in the short
rains of September – December 2015 (a) and long rains of March – August 2015 (b) at
Alupe .............................................................................................................................. 55
Figure 4.12 Number of leaves per plant among mulching treatments at Alupe during the
short rainy season (September – December 2015) and long rainy season (March – August
2015) ............................................................................................................................... 56
Figure 4.13 Effect of mulching materials on the number of branches per plant during the
short rain season of September – December 2015 (a) and long rain season of March –
August 2015 (b) at Alupe, Busia County.......................................................................... 57
Figure 4.14 Influence of mulching materials on the plant height of capsicum in the short
rains of September – December 2015 (a) and long rain season of March – August 2015 (b)
at Alupe in Busia County ................................................................................................. 58
Figure 4.15 Total fruit mass as influenced by mulching materials in two seasons of 2015 at
Alupe in Busia County .................................................................................................... 59
Figure 4.16 Average number of seeds per fruit for the long rains of March – August 2015
and short rains of September – December 2015 at Alupe in Busia County ....................... 61
Figure 4.17 Fruit length (a) and breadth (b) of green pepper as influenced by different
mulching materials in the long rains of March – August 2015 and short rain season of
September – December 2015 at Alupe in Busia County ................................................... 62
xi
ACRONYMS AND ABBREVIATIONS
ANOVA Analysis of Variance
ASL Above Sea Level
DAT Days after Transplanting
DAP Days after Planting
DM Dry Matter
HCDA Horticultural Development of Kenya
ha Hectare
g Grams
KALRO Kenya Agricultural and Livestock Research Organization
m Meter
m2
Meters squared
mm Millimeter
SAS Statistical Analytical System
WAT Week after Transplanting
WCE Weed Control Efficiency
°C Degree Celsius
xii
ABSTRACT
Green pepper (Capsicum annuum) is one of the most important and remunerative
vegetable crops. Row spacing and mulching are important factors that influence water use,
weed suppression, growth, quality, and yield of vegetables. Due to increased pressure on
land, climate change and increased demand for vegetables, there is need for deployment of
optimal agronomical practices that will ensure enough food production. This study was
undertaken to determine the optimum spacing and mulching for higher yields of green
pepper in Kenya. The experiment was conducted during the long rainy season of 2015
(March-August) and validated during the short rainy season of 2015 (September-
December) at Alupe sub-station of the Kenya Agricultural and Livestock Research
Organization (KALRO). It was laid out in a randomized complete block design with
factorial arrangement and treatments replicated three times. Two varieties of capsicum
were used, California Wonder and Yolo Wonder under three spacings (50 × 40 cm, 40 ×
40 cm, and 30 × 40 cm) and three types of mulches (black polythene mulch, transparent
polythene mulch and straw mulch) while bare soil was used as the control. Data was
collected on seedling vigor, plant height, number of leaves/plant, number of
branches/plant, number of flowers/plant, stem girth, weed species/plot, weed vigor/plot,
weeds fresh weight, weeds dry weight, fruit mass/plot, seed number/fruit, fruit length, fruit
diameter, fruit number/plant and fruit number/plot. The collected data was subjected to
Analysis of variance using SAS statistical software and where significant differences were
observed means were separated using LSD at P≤0.05. Both green pepper varieties
responded similarly to the treatment with mulching types showing significant (P≤0.05)
differences in most of the growth, weed control and yield parameters. The black polythene
mulch was the best mulch material in weed suppression by allowing the lowest weed
biomass (207 g/m2) and number of weed species (<3) while the control plot had a mean of
1629 g/m2
of fresh weed biomass and an average of 8 weed species per m2. The effect of
different plastic mulches on fruit mass per plant was significant at P≤0.05 where the black
plastic polythene mulch had the heaviest fruits during the short rains (924.5 g/plant) and
during the long rains season (649.8 g/plant). The transparent polythene mulch led to most
vigorous plant growth during the early stages while the straw mulch had the greatest vigor
in later stages. All the mulch materials were superior in suppressing the weeds compared to
the bare soil in all the sampling stages. The row spacing exhibited significant influence on
most parameters except the number of branches per plant, fruit fresh weight, fruit mass,
fresh weed biomass and average weed dry weight. The number of weed species were
highest in the widest row spacing with a mean of 5 different species per 1 m2 quadrat while
the other treatments had lower than 4 species. A maximum of 1878 g/ m2 of fresh weed
biomass was observed under the widest row spacing of 50×40 cm during the short rains
season while only 1269 g/m2 being observed on the 30×40 cm row spacing at 4 weeks after
transplanting (4 WAT). The plant spacing had significant variation in all the growth and
yield components except for fruit length. In both seasons, the number of branches per
plant, stem girth and number of fruits per plant significantly increased with increasing
plant spacing but the plant height, number of leaves per plant, fruit breadth and yield per
plant significantly increased with the decreasing plant spacing. Therefore mulching is an
appropriate technology to increase the green pepper production in Kenya and even under
the tropical conditions.
1
CHAPTER ONE: INTRODUCTION
1.1 Background study
Green pepper (Capsicum annuum) is one of the most important vegetables that are
consumed worldwide, after tomatoes and onions (Panchal, 2001). It is in the Solanaceae
family in the genus Capsicum native to South America specifically Brazil where it is
thought to be the original home of peppers (Joliffe and Gaye, 1995). It is also known as
bell pepper, capsicum, Shimla mirch or green pepper. It is a non-pungent fruit with thick
flesh and in various colors and can be eaten as cooked or raw in vegetables, as well as in
salads. It is also used for picking in brine, baking, spicing and stuffing. It contains high
nutritive value with 1.29 mg/100 g protein, 11 mg/100 g calcium, 870 I.U vitamins-A, 175
mg ascorbic acid, 0.06 mg thiamine, 0.03 mg riboflavin, 0.55 niacin per 100 g edible fruit
and 321mg per 100 g of vitamin C (Agarwal et al., 2007). They have beta carotene which
is as much as that found in spinach of 180 mg per 100 g (Olivier et al., 1981).
Green pepper cultivation is still under small scale cultivation that supplies local markets in
Kenya while a small fraction goes for export. Considering the crops’ high nutritive value
and the export potential successful cultivation in the country should be attempted (HCDA,
2010). Row spacing is one major aspect of production and proper spacing leads to
enhanced growth and development of the crop which results to maximum yields of crops
and economic land use. Yield of green pepper is dependent on the number of plants that a
given area of land can accommodate but there are however very few recommendations
regarding spacing of the crop in Kenya (HCDA, 2010).
Farmers and horticulturalists use mulching as a method of improving the conditions of
agricultural soils by covering the soil surface with different kinds of materials.
2
Improvement of the soil physical environment contributes to better plant production.
Covering the ground with mulch may add organic matter to the soil, reduce weed growth,
reduce or eliminate soil erosion, moisture conservation and that can lead to the increase of
yields (Siti et al., 1994).
Weeds impact negatively on crop productivity through interference with crop growth and
development. They also contaminate and taint farm products and change their end use.
Weed control requires more labor which limits land area for cultivation and increases the
cost of production while reducing yields. Mulching is an effective method of manipulating
green pepper growing environment to increase yield and improve quality. Crop residue
mulching provides several advantages to green pepper production (Kwon et al., 1988).
There is increased yield which is partly due to the influence of mulch to suppress weeds by
covering the surface of the soil preventing germination of the weed seeds. Synthetic mulch
is now the largest use of plastics in agriculture although its use is very minimal in the Sub-
Saharan Africa majorly because of the poverty standards (Nagalakshmi et al., 2002).
The consumption of green pepper in Kenya is increasing due to the increasing demand by
urban consumers. There is also good demand for export too. The export market needs
fruits with long shelf life, medium size, tetra lobed fruits with attractive color and good
taste. These are all qualities that should be properly maintained at the agronomical level
(HCDA, 2010). The population of the country is also alarmingly increasing and there is
need for adequate food as well as income for the farmers. This has directly put pressure on
the limited land resource and it requires proper agronomic practices that will ensure
maximum yields. But, as is the case now, the supply is insufficient to meet the above
requirements due to low productivity of the crop in Kenya.
3
1.2 Problem Statement
Although green pepper is cultivated in some parts of Kenya, yields obtained by farmers are
often very low because the agronomic research base to address yield-limiting problems like
proper row spacing and weed control has been lacking or is, at best, inadequate (Grubben
and El-Tahir, 2004). The current yield per hectare in Kenya (5.59 t/ha) is not only far
below the world averages (16.1 t/ha), but also below the average of Africa (7.9 t/ha) and
lower than eastern African countries like Tanzania (30.4 t/ha) according to FAOSTAT
(2015). Optimum plant spacing ensures proper growth and development of plant resulting
to maximum yield of crop and economic use of land. Yield of green pepper has been
reported to be dependent on the number of plants accommodated per unit area of land
(Islam et al., 2011). Weeds reduce crop productivity by interfering with crop growth and
are responsible for potential loss in most important crops worldwide (Awodoyin &
Ogunyemi, 2005). Apart from reducing crop yield, weeds contaminate and taint farm
products hence reduce their market values and change their end use. Weed control plays a
major role in pre-harvest production costs where it requires more labor which limits the
land area a farmer could cultivate at any given time (Chianu & Akintola, 2003). Weeds
compete for space, light, water and nutrients, weakening crop stand and reduce harvest
efficiency and therefore reducing crops yields (Abbasi et al., 2013). Although weed control
using mulching has always been an important component of green pepper production, its
importance has not been well researched and documented in Kenya and this has led to a
drop in yields of the crop. Considering the importance of green pepper, the cost of weeds
in terms of yield reduction, and yield advantage due to proper row spacing therefore poses
need for more information that necessitated this study.
4
1.3 Research objectives
1.3.1 General objective
The study was carried out with the aim of enhancing green pepper production through
proper agronomic practices.
1.3.2 Specific objectives
i. To determine the effect of row spacing on weed control in green pepper production
in Busia, Kenya.
ii. To determine the effect of row spacing on growth and yield of green pepper in
Busia, Kenya.
iii. To evaluate the influence of black polythene, transparent polythene and straw
mulch on weed control in green pepper in Busia, Kenya
iv. To investigate the effect of black polythene, transparent plastic and straw mulch on
growth and yield of green pepper in Busia, Kenya.
1.4 Research hypotheses
The study hypotheses were as follows:
i. Row spacing has no effect on weed control in green pepper in Kenya.
ii. There is no effect of row spacing on the growth and yield of green pepper.
iii. There is no relationship between black polythene, transparent polythene and straw
mulch in the control of weeds in green pepper.
iv. The use of black polythene, transparent polythene and straw mulch does not
influence the growth and yield of green pepper.
5
1.5 Significance of the study
This experiment sought to generate more information and knowledge on the best row
spacing that will ensure higher yields under a maximum available piece of unit land in
green pepper production. It also helps to generate information on how best mulches can be
used to suppress weed competition leading to higher yields of better quality and reducing
on the cost of chemical use and labor in controlling weeds. This also leads to conservation
of soil moisture and production of green pepper under stress prone areas and improve the
soil organic matter and structure. The farmers will be equipped with the appropriate
knowledge that will help them combat poverty by ensuring food security for their
households and improving their living standards by selling the surplus to generate more
income. This will also ensure export of the crop which will earn the country foreign
exchange that is positive to the economy.
The information is also important in other crops which are closely related to green pepper
like other capsicums, tomato and the eggplant. Lastly, the information is essential and
beneficial to the scientific pool of knowledge for reference and comparison.
1.6 Conceptual framework
This study focused on three spacing levels and three types of mulches and how they impact
on weed suppression, growth rate patterns and yield of green pepper. Proper row spacing at
planting and use of mulch and mulching techniques greatly influences the yield and quality
of green pepper.
6
Figure 2.1Conceptual Framework
7
CHAPTER TWO: LITERATURE REVIEW
2.1 Origin of green pepper
Green pepper (Capsicum annuum) is a fruit-bearing vegetable that belongs to the
Solanaceae family that also includes tomato and eggplant. Green pepper originated from
South America (Ajjapplavara, 2009). The crop is generally self-pollinating, although cross-
pollination is also common. According to Díaz-Pérez et al. (2007), green pepper is a non-
climacteric fruit which implies that it does not ripen once harvested unripe. The genus
Capsicum contains about 20 species. However, only five domesticated species are only
recognized: Capsicum annuum, C. frutescens, C. chinense, C. baccatum and C. pubescens.
All cultivated species of Capsicum have 2n = 24 chromosomes (Greenleaf, 1986). Within
C. annuum, a tremendous range in size, shape and mature colour of fruits has been selected
that now forms the basis for the types used in commerce throughout the world (Andrews,
1984; Greenleaf, 1986).
The species annuum includes eleven groups (Farris, 1988) which can be divided into two
sub group Sweet and Hot peppers. The green pepper is relatively non-pungent with thick
flesh and it is the world’s second most important vegetables after tomato (AVRDC, 1989).
2.2 Agronomic practices for green pepper production
2.2.1 Climatic requirements
Green pepper is a warm-season crop, which performs well under an extended frost-free
season, with the potential of producing high yields of outstanding quality. It is very
vulnerable to frost and grows poorly at temperatures between 5-15°C (Bosland and
Votava, 1999). The optimum temperature range for green pepper growth is 20-25°C
(Anon., 2000). The germination of pepper seed is slow if sown too early when soil
8
temperatures are still too low, but seedling emergence accelerates as temperatures increase
to between 24-30°C (Bosland and Votava, 1999). The optimum soil temperature for
germination is 29°C (Anon., 2000). Low temperatures also slow down seedling growth
which leads to prolonged seedling exposure to insects, diseases, salt or soil crusting, any of
which can severely damage or kill the seedlings (Bosland and Votava, 1999).
High temperatures adversely affect the productivity of many plant species including green
pepper. Green pepper requires optimum day/night temperatures of 25/21°C during
flowering. The exposure of flowers to temperatures as high as 33°C for longer than 120
hours leads to flower abortion and reduced yields. Pollen exposed to high temperatures
(>33°C) normally becomes non-viable and appears to be deformed, empty and clumped
(Erickson and Markhart, 2002). Temperatures lower than 16°C can lead to fruitless plants
(Coertze and Kistner, 1994). Higher yields are obtained when daily air temperature ranges
between 18-32°C during fruit set (Bosland and Votava, 1999). Persistent high relative
humidity and temperatures above 35°C reduce fruit set. Fruits that are formed during high
temperature conditions are normally deformed. Green peppers are also highly sensitive to
sunscald (Coertze and Kistner, 1994). Fruit colour development is hastened by
temperatures above 21°C (Bosland and Votava, 1999).
2.2.2 Soil requirements
Green peppers can be grown in a wide range of soils, but prefer well-drained, sandy loam
or loam soil with a good water-holding capacity and rich in humus. Soils deeper than 400
mm are required. In shallow soils with poor drainage capacity, plants can be planted on
ridges (Coertze and Kistner, 1994). Their effective rooting depth is between 400-700 mm.
Green peppers prefer soils with a pH (H2O) range of between 5.5 and 6.8 (Anon, 2000).
9
Agricultural lime should be applied to acidic soils before planting to increase the pH
(Coertze and Kistner, 1994).
Green pepper is known to be fairly sensitive to soil salinity. Green pepper yield can be
reduced by 50 percent or more with a soil electrical conductivity (EC) of 5 ds m-1
. Certain
nematode species damage pepper roots, which leads to a reduction in yield.
2.2.3 Fertilizer requirements
The fertilizer programme for green pepper production depends on the type of soil, the
nutrient status and the pH of the soil. It is therefore important to analyse the soil before
planting to determine any nutrient deficiency or imbalances (Coertze and Kistner, 1994).
The withdrawal amounts for green pepper are 1.5-3.5 kg N, 0.2-0.4 kg P and 2-4 kg K t-1
of fruit harvested (FSSA, 2007).
Nitrogen is important for green pepper plant growth and reproduction. The element is
mobile in the soil and leaches easily out of the soil. Split applications of nitrogen are
therefore necessary to minimize leaching (FSSA, 2007). On sandy soils, topdressing with
lower and more frequent split applications is necessary to reduce the risk of leaching.
Excess application of nitrogen promotes too much vegetative growth which leads to large
plants with few early fruits. Under high rainfall and humidity conditions, too much
nitrogen delays maturity, resulting in succulent late maturing fruits (Bosland and Votava,
1999). Phosphorus plays a role in photosynthesis, growth, respiration and reproduction. It
is in particular associated with cell division, root growth, flowering and ripening.
Potassium is associated with resistance to drought and cold, and fruit quality. It promotes
the formation of proteins, carbohydrates and oils (FSSA, 2007). Phosphorus is applied
before planting while potassium fertilizers are usually applied at planting time (Ngeze,
10
1998). Green pepper is sensitive to calcium deficiency, which normally results in blossom-
end rot (Pernezny et al., 2003). The crop is also sensitive to deficiency of micronutrients
such as zinc, manganese, iron, boron and molybdenum (Portree, 1996).
2.2.4 Green pepper cultivars
Many green pepper cultivars are available which ripen to colors of red, orange or yellow.
Fresh market cultivars have thick and succulent walls and should be firm and bright in
appearance (Bosland and Votava, 1999). Cultivars for processing have fruit that are firm,
flat (with two locules), smooth, thick-fleshed, bluntly pointed and about 150 mm long and
40 mm wide at the shoulders (Bosland, 1992).
Figure 2.1 Green pepper varieties: A-Maxibell; B-Admiral F1; C-Buffalo F1; D-California
Wonder; E-Yolo Wonder and F-Orange Pepper
11
California Wonder 300, the green pepper cultivar used in this research is a popular open
pollinated sweet green pepper cultivar suitable for open field production. It reaches
maturity approximately 73-75 days after transplanting and colors from green to red when
over-ripe. The fruit has a bell shape with mostly four lobes and has a size of about 100 x
100 mm (Anon, 2000). The cultivar has an exceptionally smooth skin, attractive
appearance and dark green colour. The approximate plant height of this cultivar is 710-810
mm. This cultivar is suitable for both fresh market as well as processing (Anon, 2000).
‘Yolo Wonder’ (Heirloom, 80 days), the green pepper cultivar also used in this research, is
probably one of the most frequently seen green pepper varieties in markets. Green blocky
fruits with a maturity period of 80 days from transplanting, the average fruit weight 100-
120 grams and yield potential of 6 tonnes per acre. The plant is a vigorous, erect and
compact plant adapted to warm climatic conditions with deep green colored fruits. Very
productive plants with good leaf cover to reduce sun scald. Also important is Yolo Wonder
variety which is characterized with large, green, thick-walled fruit, heavy yield. Yolo
Wonder is known for growing to a height of approximately 1.46 feet (that's 45.0 cm in
metric). It is normally fairly low maintenance and is normally quite easy to grow, as long
as a level of basic care is provided throughout the year (Aliyu, 2002).
2.3 Importance of green pepper
Bell peppers are grown for both fresh and processed markets. These include varieties with
the traditional “blocky” three to four lobe shape as well as longer more pointed varieties
known as European Lamuyo types. Both hybrid and open-pollinated varieties are popular,
with a trend toward greater use of hybrids. Hybrids have a high seed cost. To control costs,
growers use transplants rather than direct seed. Open-pollinated varieties can be either
12
transplanted or seeded in the field. China produces the largest quantity of green peppers
followed by Mexico, Turkey, and Indonesia. The United States ranks fifth in the global
production of green peppers.
Green pepper is used either green or red, and may be eaten as cooked or raw, as well as in
salad. It is also used for pickling in brine, baking and stuffing. The leaves are also
consumed as salad, soup or eaten with rice (Lovelook, 1973). It was also discovered to be a
good source of medicinal preparation for black vomit, tonic for gout and paralysis (Knott
and Deanon, 1967). It is used in fresh salads, to add flavors to dishes and for canning
(Olivier et al., 1981). On the nutritional part, it is rich in Vitamin C (ascorbic acid) and
zinc, the two nutrients which are vital for a strong and healthy immune system. It also has
high content of Vitamin A, rutin (a bioflavonoid), ß carotene, iron, calcium and potassium
(Agarwal et al., 2007). Green pepper has a little energy value. But the nutritive value of
green pepper is high as it contains 1.29 mg protein, 11 mg calcium, 870 I.U vitamin-A, 175
mg ascorbic acid, 0.06 mg thiamine, 0.03 mg riboflavin and 0.55 mg niacin per 100 g
edible fruit (Joshi and Singh, 1975). The vitamin C content was found as high as 321 mg.
2.3.1 Green Pepper Production in Kenya
Green pepper production is still low compared to other countries that fully grow the crop
and the potential it possesses. In central region this crop is mainly grown in green houses.
The crop has high demand especially the yellow variety. Eastern, Rift valley and Nairobi
regions the production has gone down. However in Central, Coast, Nyanza, western and
North Eastern the crop has increased. According to a report by the Horticultural Crop
Development Authority of Kenya (2010) the average fresh yield of green pepper in Kenya
ranges between 8-10 tons per hectare as shown in the figure below.
13
Figure 2.2 Capsicums production in Kenya for period 2006-2010 (HCDA, 2010)
2.4 Effect of row spacing in green pepper production
Successful cultivation of any crop depends on several factors. Sowing date and plant
spacing are the important aspects for production system of different crops. Optimum
sowing and plant spacing ensures proper growth and development of plant resultant to
maximum yield of crop and economic use of land. Yield of green pepper has been reported
to be dependent on the number of plants accommodated per unit area of land (Duimovic
and Bravo, 1979).
Plant population and plant spacing can greatly influence plant development, growth and
marketable yield of green pepper. Many studies have been published on the optimum plant
population of bell peppers for example green pepper plant population recommended in
South Africa is between 20,000 and 55,000 plants ha-1
(Locascio and Stall, 1982) but in
Kenya such information is limited.
14
A study by Yildiz and Abak (2003) on plant density also showed significant effect on
growth and development. Cushman and Horgan (2001), on their study on the effect of 4
plant populations viz, 29040, 14520, 9860 and 7260 plant per acre with 0.5, 1.0, 1.5, 2.0
feet distance between plants in each row, concluded that 9860 plant per acre was the
optimum population. Similar studies showed that, by increasing plant density, salable
product will increase linearly (Cavero et al., 2001; Yildiz and Abak, 2003). Yildiz and
Abak (2003) suggested that plant yield can be variable in high density according to branch
numbers per plant, and proposed that 80 × 15 cm is the best distance for each plant.
Aliyu (2002) conducted a field trials with pepper (Capsicum annuum) cv. L5962-2
between 1991 and 1993 at Samam, Nigeria, to study the effect of N (0, 80, 160, 240 and
360 kg/ha), P (0, 22 and 44 kg/ha) and plant density (20000, 40000 and 60000 plants/ha)
on the growth and dry fruit yield. Although yield per plant decreased with increasing plant
density, the yield/ha increased up to 60000 plants/ha.
Plant population and layout can have an evident influence on plant development, growth,
and marketable yield of many vegetable crops including green pepper (Cavero et al.,
2001). The relationship between plant population and growth can be complicated since
growth is a function of the plant genotype (Lower et al., 1983). The closeness of
neighboring plants affects their interactions within the root and shoot micro-environments.
If such interactions happen to be competitive or allelopathic, plant growth and
development might be affected. Optimum plant population of a crop should be lower under
inadequate soil water conditions. The opposite is also true, plant population can be higher
under well-watered conditions.
15
Arora et al. (2002) conducted field experiments comprising of six plant densities and four
irrigation levels to study their effect on shoot-root growth and fruit yield in chilli cv. HC-
44 during 1994 and 1995 where among various levels of plant densities tested, D5 (24
plants/plot) produced maximum dry weight of leaves, root length and root biomass
whereas D4 (60 plants/plot) produced maximum fruit yield (q/ha). Among the irrigation
levels tested 13 (ID/CPE ratio of 1.0) gave maximum dry weight of leaves and fruit yield
(q/ha) while 12 (ID/CPE ratio of 0.75) gave maximum root length and root biomass. The
interaction effect of plant density and irrigation levels showed that D4I3 (60 plants/pot
with irrigation level having ID/CPE ratio of 0.75) resulted in maximum yield of red ripe
fruits while least was recorded in D5I3 (24 plants/plant with ID/CPE ratio of 1.0).
As Leaf Area Index (LAI) of a crop increases under high plant populations, light
interception improves and consequently increases photosynthesis, resulting in a higher
biomass and yield. However, Meyer et al. (1973) also reported that under very high plant
populations, leaves overlap and thereby shade each other, causing inadequate light
interception and a decrease in photosynthesis. Low plant populations or any other factor
such as pests, diseases and hail causing a low Leaf Area Index, decrease the efficiency of
light absorption and photosynthesis.
The effect of spacing and planting method on the yield of green pepper was studied in an
unheated plastic tunnel (Dobromilska, 2000). Green pepper transplants were planted at a
density of 50x40 cm, 50x50 cm and 50x60 cm, in single or double rows. Plants grown at
50 * 40 cm in double rows produced the highest total fruit yields and yields of first class
fruits. However, the commercial quality of fruits (mean weight, thickness of pericarp) was
lower at the highest planting density.
16
Stoffella and Bryan, (1988) studied the influence of plant population and arrangement on
the growth and yield of green pepper in southern Florida during the winter of 1983 and
spring of 1984. Populations ranged from 21,500 to 258,000 plants ha-1
. Marketable fruit
yield ha-1
increased linearly in response to higher plant populations. However, marketable
fruit number and mass per plant decreased with higher plant populations, whereas fruit size
(g fruit-1
) was unaffected. The higher marketable yield ha-1
at higher plant populations was
attributed to more plants with less of the same sized fruit per plant. A plant population of
86,000 plants ha-1
was therefore recommended for green peppers.
Agarwal et al. (2007) investigated the influence of plant population on the productivity of
green pepper (Capsicum annuum L.) in a greenhouse under full irrigation. Different
populations (50,000, 62,500, 83,333, 100,000, 111,111, 160,000 and 200,000 plants ha-1
)
were planted per bed with four rows per bed. Fruit number and yield per plant decreased
when plant population increased from 50,000 to 200,000 plants ha-1
. Total fruit yield per
hectare increased with an increase in plant population up to 120,000 plants ha-1
and
thereafter it decreased, as was the marketable fruit yield. Individual fruit mass was
however not influenced up to a plant population of 120,000 plants ha-1
but decreased fast
beyond this plant population. The increase in fruit number per plant and individual fruit
mass as a result of increased plant population may be ascribed to better utilization of
available natural resources such as light and nutrients. Plant populations in the range of
100,000 to 120,000 plants ha-1
were optimum in terms of yield and quality.
In an experiment carried out by Jolliffe and Gaye (1995) consisting of three trials with five
plant populations (1.4, 1.9, 2.8, 5.6 and 11.1 plants m2) and different row covers, the total
and marketable fresh green pepper yield displayed a linear increase with an increase in
17
plant population. Plant population also significantly influenced fruit dry mass per unit area
from 76 days after transplanting onward. As much as 47% of total yield difference was
attributed to population effects.
Capsicum annuum var. grossum cv. California Wonder was sown at different densities
(60x30, 60x45 and 60x60 cm spacing) and was supplied with 4 N rates (0, 50, 100 and 150
kg/ha) and 3 P rates (0, 50 and 100 kg/ha) in a field study conducted at Coimbatore, Tamil
Nadu, India. Leaf Area Index (LAI) was the highest at 60x45 cm spacing. Net assimilation
rate (NAR), relative growth rate (RGR) and crop growth rate (CGR) increased as
population densities increased and were the highest at 60x30 cm spacing. Harvest index
was the highest at 60x60 cm spacing. LAI, total chlorophyll content and harvest index
were the highest when 150 kg N/ha + 100 kg P/ha was applied. NAR, RGR and CGR were
not affected by N and P rates (Maya et al., 1999).
Kim et al. (1999) investigated the effect of planting density (2479-6198 plants/1000 m2) on
growth, yield and fruit quality of Capsicum (cultivars viz Pungchon (upright) and
Shinbaram (spreading), grown in tunnels. Seedlings were planted in 2-rows on a raised-
bed, either facing each other or alternating, and were spaced 20, 30, 40 or 50 cm apart.
Planting systems and distances did not significantly alter plant height, main stem length,
fruit length, fruit diameter or thickness of pericarp. However, increasing the distance from
20 to 50 cm increased stem diameter. Planting distance, but not the planting pattern,
affected fruit number/plant while the total yield increased as planting density increased.
Some differences were found in fruit powder chromaticity, ASTA colour and the
concentrations of capsaicinoids and sugars, but no consistent conclusion, ascribed solely to
planting patterns and distances, could be drawn. Since increasing planting density did not
18
reduce fruit size or the quality of pepper powder, it is an acceptable way to increase the
yield of tunnel-grown Capsicum.
Ravanappa et al. (1998) investigated the effect of plant density (60x30, 60x45, 60x60,
75x30, 75x45, or 75x60 cm) on growth and yield of 3 green chilli (Capsicum) cultivars
(Nagavi, Kadrolli and Pusa Jwala) using factorial design at Dharwad, India, during
summer 1991 and Kharif season (monsoon) 1992. Significant cultivar and treatment
differences were noticed. The variety Nagavi produced the highest number of branches of
all orders, fresh weight and dry weight of plants, and the highest green fruit yield. The
highest plant density treatment (60x30 cm) produced the highest yield/ha, while the lowest
plant density treatment (75x60 cm) produced the highest DW, FW, number of branches
and yields/plant.
Pepperrocini pepper (Capsicum anmium var. anmium cv. Golden Creek ) was grown at the
spacing’s of 7.5, 22.5, 30 and 45 cm to determine the effect of plant population on growth
and fruit yield in a 2 year field study (Motsenbocker, 1996). In 1992, pepper plants grown
at 15 cm in-row spacing had the lowest plant, stem and leaf DWs, while plants at the
lowest density (45 cm spacing) had the highest plant, leaf and stem DWs, and the largest
leaf area (LA). Total yields of fruit count/ha were the highest for plants grown at the 7.5
cm spacing, but fruit yield/plant was the lowest. In 1993, the lowest plant and leaf DWs
and LA and the highest LAI were obtained from plants at 7.5 cm in-row spacing. Plants at
the 45 cm spacing had the highest plant and leaf DWs and LA and the lowest LAI. Pepper
plants grown at the closest spacing produced the lowest early and total fruit yields/plant,
but the maximum yield of fruits/ha.
19
Cebula et al. (1995) conducted an experiment in greenhouse. Capsicum annuum Plants
(vb. Bendigo FL) were spaced at 1.5. 3.0, or 6.0 plants/m and pruned to 4, 2 or 1
shoot(s)/plant, respectively to give a constant 6 shoots/m2. Similarly, a shoot density of 8
shoots/m2 was produced from 2, 4 and 8 plants/m
2 pruned to 4, 2 and 1 shoots/pant,
respectively. The number of leaves/plant was positively correlated with the number of
shoot(s)/plant. Limiting shoot number/plant, while proportionally increasing plant
population resulted in more effective coverage of soil by the canopy. The transmittance of
photosynthetically active radiation in the plant profile was more beneficial with plants at a
wider spacing, but with a higher number of shoots/plant. Early and total yields/unit area
increased with plant density; plants with 1 shoot at a density of 8 plants/m2 produced the
highest yield. There were no treatment effects on quality.
Jankulovski et al. (1995) reported that, three cultivars of peppers (Zelaten Medal, Bela
Dolga and L-10/34) were grown in 2-row strips or in ordinary rows at 4 different spacings,
equivalent to 11.1, 8.3, or 6.6 plants/m2 in all three cultivars, earliness and yields were best
with a plant density of 11.1 plants/m2 . The spacing recommended for commercial
production is 11.1 plants/m2 in 2- row strips, or 8.3 plants/m
2 also in 2-row strips.
2.5 Effect of mulching materials on growth and yield of crops
According to Unger (1995), mulching is defined as the soil surface application of any
material that was grown and maintained in place, grown, but modified before placement, or
processed or manufactured and transported before placement. Pickering et al. (1998)
defined mulch as any material which, when spread on the ground, has a modifying
influence on the characteristics of the underlying soil.
20
Any material used (spread) at surface on soil to assist soil and water conservation and soil
productivity is called mulch. The word mulch has been probably derived from the German
word “molsch” means soft to decay, which apparently referred to the use of straw and
leaves by gardeners as a spread over the ground as mulch (Ossom et al., 2003). The
practice of applying mulches to soil is possibly as old as agriculture itself. Mulches are
used for various reasons but water conservation and erosion control are the most important
objective for its use in agriculture in dry regions (Shinde et al., 1999). Other reasons for
high mulching use includes soil temperature modification, soil conservation, nutrient
addition, improvement in soil structure, weed control and crop quality control (Hochmuth
et al., 2001). Mulching facilitates more retention of soil moisture and helps in control of
temperature fluctuations, improves physical, chemical and biological properties of soil, as
it adds nutrients to the soil and ultimately enhances the growth and yield of crops (Easson
and Fearnehough, 2000). Mulches are either organic or inorganic. Organic mulches are
those derived from plant and animal materials. Those most frequently used include plant
residues such as straw, hay, peanut hulls, leaf mold and compost, wood products such as
sawdust, wood chips and shavings and animal manures. Organic mulch properly utilized
can perform all the benefits of any mulch with the possible exception of early season soil
warming. However, natural mulch materials are often not available in adequate quantities
for commercial operations or must be transported to the place of use (Ravinder et al.,
1997).
Natural materials cannot be easily spread on growing crops and require considerable hand
labour. Expense and logistical problems have generally restricted use of organic mulch in
crop production and gardening of fruit plants with only limited use on a large commercial
21
scale. Inorganic mulch includes plastic mulch and accounts for the greatest volume of
mulch use in commercial crop production (Hochmuth et al., 2001). The plastic materials
used as mulch are poly vinyl chloride or polyethylene films. Owing to its greater
permeability to long wave radiation it can increase temperature around the plants during
night in winter. Hence, polyethylene film mulch is preferred as mulching material for crop
production. Application of black plastic mulch film is becoming popular and very good
results have been achieved particularly in rainfed agriculture (Hochmuth et al., 2001). Use
of polyethylene mulch has been reported to conserve soil moisture appreciably. The black
polyethylene mulch also checks all types of weeds in addition to soil moisture
conservation, therefore, black plastic mulch is more beneficial (Ravinder et al., 1997).
Plastic mulches have various beneficial effects on crop product in arid regions, including
an increase in soil temperature, texture and fertility and the control of weeds, pests and
diseases. The beneficial effects of organic and synthetic mulches for crop production have
been widely discussed by Ravi and Lourduraj (1996).
Soil water content, temperature, structure and salinity are probably the most important
aspects associated with agriculture in semi-arid and arid regions. Beneficial effects of
surface mulches on soil structure result primarily from mulches absorbing the energy of
falling raindrops, thus reducing soil dispersion and surface sealing. Infiltration rates are
therefore maintained and subsequent crusting is reduced. Since salts readily move with soil
water, a practice that maintains infiltration rates and reduces subsequent evaporation
should control the undesirable effects of soil salinity (Panchal et al., 2001).
Kirnack et al. (2003) investigated the effects of mulch and different water regimes on
green pepper. Four treatment combinations namely: bare soil and water stressed (WS);
22
bare soil and unstressed (control); black polyethylene mulch and water stressed (BPM +
WS) were investigated. Fruit yield, fruit mass, fruit number per plant and water use
efficiency (WUE) were significantly reduced by water stress as compared to the control.
They also found that green pepper’s water use efficiency was significantly reduced by
water stress as compared to the combination of water stress and black polyethylene
treatments. The water stress and black polyethylene treatment had the highest plant water
use efficiency and was significantly better than the control and the water stressed
treatments.
Agele et al. (2000) studied the effect of tillage and mulching on the performance of post-
rainy season tomato in the humid, south of Nigeria. They indicated that soil temperature
reduction and improved soil water content were the factors responsible for increased
tomato yield as a result of mulching. In the study it was found that Mulching significantly
improved the growth and yield performance of tomato compared to no mulch. Application
of grass mulch significantly increased shoot dry mass, leaf area, flowering, fruit set and
fruit yield. This observation may be attributed to the favorable soil temperature and soil
water status created by mulching. Higher soil temperature and lower soil water content in
bare ground could have adversely affected tomato yield due to increased fruit abortion,
inadequate photosynthate supply during fruit set and increased intensities of soil water
deficits late in the season. Mulching also prolonged the growth period by delaying the
onset of flowering and harvesting of tomatoes by 4 and 9 days, respectively. Shorter
growth season (increased earliness) in the bare ground treatment was related to a low soil
water status and this agrees with findings in terminal drought situations. Early maturity in
23
crops increases the likelihood of water availability for the completion of the reproductive
growth before the onset of drought-induced senescence (Agele et al., 2000).
2.6 Importance of mulching in weed suppression and control
Weeds reduce crop productivity by interfering with crop growth and harboring pests. They
also contaminate and taint farm product to reduce their market values and change their end
use. Mulching is an effective method of manipulating crop growing environment to
increase yield and improve product quality by controlling weed growth, ameliorating soil
temperature, conserving soil moisture, reducing soil erosion, improving soil structure and
enhancing organic matter content (Awodoyin and Ogunyemi, 2005). Awodoyin and
Ogunyemi (2005) have reported that the weed control efficiency of different types of
mulch in cayenne pepper production ranged from 27% to 97%. Physical methods for
weeds suppression are the methods suggested by integrated non-chemical weed
management strategy and are very useful and herbicide free weed control methods
worldwide are getting more attention due to environmental and ecological factors.
Plastic mulch has been used on peppers production since the early 1960’s. Some of the
advantages of mulches are earlier yield, increased water retention, inhibition of weeds,
reduced fertilizer leaching, decreased soil compaction, fruit protection from soil deposits
(from splash) and soil micro-organisms and facilitation of fumigation. Plastic mulches are
often used in combination with drip irrigation when establishing seedlings. Plastic mulches
have been shown to raise soil temperatures and increase fruit quality (Bosland and Votava,
1999). Organic mulches which include lawn clippings, chopped sorghum and sugar cane
leaves are also used to improve and increase vegetable production (Messiaen, 1992).
24
Mechanical and physical weed management methods that are widespread in ecological
farming have significant expenses, so we need to examine other methods under local
circumstances to save expenses. The use of living plants, plant residues (straw, compost,
mowed grass, processing by-products) and industry-origin materials (black polyethylene
foil, paper, felt, different kinds of textile) as mulch. Each mulching material has different
weed control effect. Black foils is one of the most standby methods for weed control but as
its disadvantage we have to mention that we have to remove if it is a non-degradable foil.
In Western Europe organic mulch is prevalent. Grass, leafage, straw and mowed weeds are
used for inter-row covering. Besides its shading effect it can provide nutrients to the soil.
One of the most former mulches is straw, by-product of plant production. In India, straw
mulch increased yield of crop and water keeping capacity of the soil (Moitra et al., 1996).
According to Tu et al. (2001.) straw mulch is not advisable for controlling of perennial
weeds, because these plants accumulate much nutrient and break through the covered
surface easily. Otherwise in the case of cirsium (Cirsium arvense) thick straw mulch
decreased the number of flowering plants.
The use of paper mulch started in the 1970’s (Vandenberg and Tiessen, 1972) but was
replaced by polythene because of its better mechanical properties in elasticity and avoiding
water evaporation. The disadvantages of polythene caused a new interest in paper mulch
and at present, the most recent research in Italy focus on paper coated with other materials
as blends based on polyhydroxyalkanoates (Salemi et al. 2008). The main disadvantages of
using paper mulch are the heavier coils, slower mulching speed and the need for a careful
installation to avoid fractures (Harrington and Bedford, 2004). However, an interesting
25
property of paper mulch is the ability to control C. rotundus (Shogren and Hochmuth 2004;
Anzalone et al. 2010).
2.7 Influence of the integration of row spacing and mulching on crop production
Znidarcic and Osvald (1999) conducted an experiment to show the effects of plant density
and polypropylene covers on the marketable yield of bell peppers. Plants of cv. Soroksari
were transplanted at 4 densities of 21.8, 13.2, 10.9 and 6.6 1/2 plants/m. All plants were
grown on soil covered with black PE film. The treatments consisted of covered plants in
comparison with an uncovered control. Mean daily air temperatures under the covers were
2.3-5.8°C higher than outside temperatures. Covers were removed after 8 weeks when
mean daily maximum temperatures exceeded 32°C. Yield component analysis indicated
that fruit size was larger under covered treatments in comparison to uncovered treatments
at all plant densities. Total marketable yield/m was significantly higher under cover. In
addition, increasing plant density enhanced total marketable yield. The interactions of
cover and density were not significant for total marketable yield. The strongest influence in
terms of an earlier yield was the covered crop at the second harvest on August 25. At this
harvesting, the covered treatments had a 109% higher yield than uncovered treatments. The
total accumulated marketable yield under cover was 71.8% greater than with no cover.
The same authors (Ravanappa et al., 1998a) indicated that, plant height and spread were
the greatest in Kadrolli and the lowest in the dwarf genotype Nagavi. Nagavi, however,
gave the highest yields (91.73 q/ha in summer and q/ha in Kharif). Plant height was the
greatest and plant spread and girth were the least with the highest plant density. Yield
(q/ha) was also the highest with the highest plant density and decreased with decreasing
plant density.
26
Ravanappa et al. (1998b) observed significant cultivar differences with regard to root
parameters, flowering and yield. The highest yield in summer and kharif obtained from
Nagavi had the highest root weight. Kadrolli had the lowest yield. Among spacing
treatments, the closest planting resulted in the highest yield (87.5 q/ha in summer and
113.1 q/ha in Kharif), while the widest spacing resulted in better root length and weight.
Viloria et al. (1998) conducted a field trial in 1995 in Venezuela with Capsicum annuum
cv. Jupiter. Seedling of 35 days old were transplanted in raised beds (18x1.2x0.40 m),
filled with a mixture of soil, horse manure, sand and coconut fiber (2:1:1:1, by volume).
Plant spacing’s of 10, 15 and 20 cm were used, with rows 60 cm apart. With the reduction
of the planting distance from 20x60 to 10x60 cm, the values of the parameters evaluated
decreased significantly, except for stem heights. Age (days after planting) was statistically
significant for all the variables except the height of the main stem, which showed that the
period between 35 and 80 days after transplanting is determinant on the growth of the bell
pepper plant structures. The responses of growth variables were explained by multiple
exponential and linear equations.
Maya et al. (1997) conducted in field trials at Coimbatore, Tamil Nadu, India, with green
pepper (Capsicum anmium var. grossum) cv. California Wonder. Seedlings were planted at
spacings of 60 x 30, 60 x 45 or 60 x 60 cm supplied with 0, 50, 100 or 150 kg N and 0, 50
or 100 P kg /ha. Plant height, dry matter production and yield per hectare at the closest
spacing of 60 x 30 cm. The highest yield (12-13 t/ha) was achieved with a plant spacing of
60 cm x 30 cm and with N and P application rates of 150 and l00 kg/ha, respectively.
27
CHAPTER THREE: MATERIALS AND METHODS
3.1 Description of study area
The study was conducted at KALRO (Kenya Agricultural and Livestock Research
Organization), Alupe Sub-station located in Busia County (Figure 3.1) which lies on
longitude 34° 07’ E, latitude 0° 29’ and altitude of 1,189 m above sea level and receives an
average annual rainfall of between 1500 mm-1850 mm with an annual mean temperature
of 30 °C.
The study was carried out during the long rainy season of 2015 (Season one) which
occurred between March and August and repeated during the short rainy season of the
same year (Season two) which occurred between September and December to validate the
results. Major soil types are orthiferrosols, partly petroferic with orthicacrisols (Jaertzold et
al., 2006). Soil samples were taken from the field for analysis to determine the soil pH and
essential nutrient contents (N, P and K). The soils were found to be low in nitrogen
(0.08%) and phosphorus (10 ppm) which were uniformly applied in all experimental units
to ensure proper growth nutritionally.
28
Figure 3.1 The study site in Alupe Crops Research Station in Busia County
3.2 Experimental design and treatments
The experiment was laid out in a randomized complete block design (RCBD) in a 3×4×2
factorial arrangement with three different row spacing levels (50 × 40 cm, 40 × 40 cm, 30
× 40 cm); three types of mulches (black polythene (0.25 μm), transparent polythene (0.25
μm), straw mulch, and bare soil); and two varieties (California Wonder and Yolo Wonder).
Bare soil was used as the control plot. The treatments were replicated three times thus there
were 72 plots in the experiment. Each experimental unit measured 2 m × 1.6 m. Weed
identification was carried out for each plot before planting. Soil sub-samples were
collected using a soil auger in a zigzag pattern from at a depth of 0-30 cm from each
experimental field and mixed to create a core sample that was analyzed at the KEPHIS
Laboratories (Nairobi). Seedlings were transplanted after thirty days in the nursery bed to
the main plots. The black plastic polythene and transparent plastic polythene mulches were
KALRO-Alupe
29
laid just before transplanting with the straw mulch, sourced from dry finger millet
(Eleusine coracana) straw was spread to a 2 cm thickness on the plots just a day before
transplanting. Transplanting holes were made at pre-marked points on the plastic mulches.
The transplanted seedlings were watered right at transplanting (20 L per plot) and on
subsequent days, at least twice a day (early morning and evening), depending on the soil
moisture content. Pest and diseases were controlled by pesticide application during growth
and development of the plants. Plant protection was part of the field practices where
cultural and chemical control measures were taken and brought about successful results.
Cutworms occurred during the early seedling establishments on the actual field, whereas
bacterial wilt was a problem at vegetative and subsequent plant development stages on
both varieties but controlled through an integrated pest management program. All other
agronomic practices were conducted as recommended.
3.3 Source of planting materials, nursery management and transplanting
Seeds of green pepper (variety: California Wonder and Yellow Wonder) were obtained
from Simlaw Seeds in Malaba Town. A basal dose of 2 kg of well-rotted poultry manure
was applied to the 1.2m×1.2m bed. The seeds were sown on 11th
February, 2015 on well
prepared beds and watered. A shed made from palm fronds, was erected on top of the beds
to provide shade to protect the seedlings from harsh weather conditions. Watering was
carried out every other day depending on the climatic conditions. Hand picking of weeds
and stirring of the soil to enhance aeration were carried out regularly. Neemazal (neem
seed oil) with active ingredient azadirachtin, an organic insecticide and Shavit F 71.5 WP
fungicide at the rate of 1g per litre of water were used to control pests and fungal diseases
respectively. Uniform and healthy seedlings which were 3, 4 and 5 week-old after pricking
30
out were transplanted to the respective spacings on 23rd
March, 2015 early in the morning
to reduce excessive loss of water from the transplants. Seedlings that were cut by crickets
in the first two weeks after transplanting were continually replaced until the plants were
well established.
3.4 Data Collection
3.4.1 Growth parameters
i. Seedling vigor
The crop was visually observed at 3 weeks after transplanting on its vigor and recorded on
a scale of 1-3 whereby 1 was vigorous 2 was intermediate and 3 was poor.
ii. Plant Height
The height of plant was taken in centimeter (cm) from ground level to the tip of the stem of
the plant at two weeks interval and during the final harvest.
iii. Number of branches
Total number of all the primary branches were counted from each of the selected plants
and their average value was taken as number of branches per plant.
iv. Number of leaves per plant
The number of leaves per plant was counted from the selected plants and their average was
taken as the number of green leaves per plant.
v. Stem girth
Girth of stem in centimeter (cm) was recorded for each of the five randomly selected
plantsat final harvest at the base portion of the plant with a slide calipers.
31
3.4.2 Weed parameters
i. Weed species
The number of weed species in every experimental unit per m2 quadrat was counted and
recorded at every weeding.
ii. Weed vigor
The vigor of weeds was recorded from each experimental unit per m2 quadrat at every
weeding using the scale of 1-3 where 1 was most vigorous, 2-intermediate and 3-poor.
iii. Weed Fresh weight (g)
Hand weeding was done on each experimental plot and the fresh weight of the weeds
measured where the above-ground parts within each plot were clipped with a secateurs at
soil surface.
iv. Weed Dry weight (g):
The fresh weeds collected from every plot and oven-dried at 80oC for 48 hours and
weighed with a digital balance (model P1210) to determine the weed dry weight.
3.4.3 Yield Parameters
i. Number of fruits per plant
Fruits were collected at different dates from the selected plants and their average taken as
the number of fruits per plant.
ii. Average number of seed per fruit
Seeds of randomly picked ten marketable fruits from sample plants were removed using a
scalpel and counted then the mean recorded.
32
iii. Total fruit yield (g)
Weight of total (marketable and unmarketable) fruits harvested at each successive
harvesting from the sample plants was recorded at each harvesting.
iv. Fruit diameter (cm)
Breadth of the fruits were measured at the middle portion of 3 selected fruits (large,
medium and small size) from each plot with the digital slide calipers in centimeter and
their average was taken as the breadth of the fruits.
v. Fruit length (cm)
The length of the fruit was measured with a digital slide calipers in centimeter from the
neck of the fruit to the bottom of the fruit. It was measured from 3 selected fruits (large,
medium and small size) in each plot and their average was taken as the length of the fruit.
vi. Number of fruits per plot
Fruits were collected at different dates from all plants per plot and per replications.
Number of fruits per plot from first harvest to final harvest was collected to get total
number of fruits per plot.
vii. Individual fruit weight (g) and yield per plant
Mean fruit weight in gram was calculated from the 3 selected fruits weight and also these
fruits were taken to measure the size of fruit. Yield per plant was calculated in gram by a
balance from the total weight of fruits per selected plants harvested at different periods and
was recorded.
33
3.5 Data analysis
A two-way analysis of variance (ANOVA) was performed on the results collected from the
experiment using SAS computer software version 9. Associations between the variables
were considered significant at P≤0.05. Treatment means for each parameter where
significant differences were observed were separated by the Fischer’s Protected least
significant difference (LSD) test at P ≤ 0.05.
34
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Effectiveness of row spacing in control of weeds in green pepper
4.1.1 Number of weed species
The row spacing treatments showed significant differences (P≤0.05) on the number of
weed species for both seasons at 4 weeks after transplanting (4 WAT) and between spacing
treatments on both varieties (Fig. 4.1). The highest number of weed species per m2 (5) was
recorded on the widest row spacing (50×40 cm) during both seasons while the narrow row
spacing of 30×40 cm had the lowest weed species during the long rains season, though
during the short rains season there was no significant differences between the 50×40 cm
and the 40×40 cm row spacing. The difference in the number of weed species between the
treatments was majorly attributed to quicker canopy closure and reduction in light
penetration that occurs in narrow compared to wide-row spacing, which subsequently
cause reductions in weed seed germination and/or growth later in the season. Other authors
have found that environmental conditions that do not favor rapid canopy closure, such as
lack of rainfall, can result in similar late-season weed density in narrow-and wide-row
(Buehring et al., 2002) which explains the variation in responses observed.
35
Figure 4.1 Number of weed species per unit quadrat (m2) during the long and short rainy
seasons of 2015 at Alupe at 4 WAT (WAT-Weeks after transplanting). Row spacing is in
cm.
In addition to effects on weed resurgence, row spacing had a profound impact on the
critical period of weed control in green pepper. The critical period of weed control is an
interval of time in the growth of a crop during which it is essential to control weeds in
order to prevent unacceptable yield losses. The beginning of the critical period of weed
control is determined by the critical time of weed removal, which is the time at which
weeds must be removed because the crop can no longer withstand early season weed
competition and will begin to suffer irrevocable yield losses which under the current
experiment it was found to be at 4 weeks after transplanting where the highest number of
weeds and density was recorded and should start on the widest row spacing compared to
the narrow row spacing. Similarly, Mulugeta and Boerboom (2000) found that the critical
time of weed removal occurred much earlier in wide- compared to narrow-row spacing.
36
4.1.2 Weed vigor
On a scale of 1-3 where 1 was the most vigorous, the weeds were found to be most
vigorous on the widest row spacing (50×40 cm) as shown in Fig. 4.2. The narrow row
spacing (30×40 cm) showed the lowest vigor of weeds during both seasons. The 40×40 cm
row spacing had an intermediate weed vigor which was significantly different but closer to
that of the 30×40 cm row spacing treatment. Narrow row spacing probably led to higher
leaf photosynthesis of California Wonder and Yolo Wonder varieties due to the higher
crop-weed competition which in turn increased the suppression of weed growth by
smothering effect compared to wider row spacing (Dwyer et al., 1991). The reduced weed
vigor can be explained from the fact that in case of higher population density, penetration
of light was decreased between the rows due to enhanced growth of the plants which due to
competition tended to grow faster in order to outperform the nearby crops and the weeds
that had germinated in the treatment. Teasdale and Frank (1983) reported higher seed yield
and improved weed suppression when snap beans were grown in 46-cm rows rather than
91-cm rows. Additionally, when weeds were controlled for the first half of the season,
weed suppression was 82% higher in 15-to 36-cm rows than in 91-cm rows. Similar
findings have been reported for other crops (Howe and Oliver, 1987).
37
Figure 4.2 Weed vigor of green pepper during the long and short seasons at Alupe in 2015
at 4 WAT (Weeks after Transplanting)
4.1.3 Fresh weed biomass
The highest fresh weed biomass was recorded 4 weeks after transplanting (4 WAT) in both
green pepper varieties showed significant differences (P≤0.05) between the row spacing
treatments for both seasons (Table 4.1). The highest fresh weed biomass was found on the
50×40 cm row spacing of 834.3 and 1878 g/m2 for the long and short rains seasons
respectively. The fresh biomass of weeds dropped as the weeks progressed with the widest
row spacing having the highest biomass yield. The 30×40 cm and 40×40 cm row spacings
also differed significantly (P≤0.05) at 6 WAT while the narrow spacing (30×40 cm) had
the lowest fresh weed biomass at 8 WAT for both seasons. Malik et al. (1991) reported
similar findings to the current study showing that the ability of bean cultivars to reduce
weed biomass was further enhanced in medium and narrow rows compared to traditional
wide rows.
38
Table 4.1Fresh weed biomass per quadrat (m2) during the long and short rainy seasons of
2015 at Alupe under different plant spacing (cm) at 4, 6 and 8 WAT (Weeks after
transplanting)
4 WAT 6 WAT 8 WAT
Long
Rains
Short
Rains
Long
Rains
Short
Rains
Long
Rains
Short
Rains
30*40 613c 1269b 589b 415b 329c 285c
40*40 728b 1508ab 605b 481b 413b 346b
50*40 834a 1878a 819a 682a 534a 465a
P-Value 0.007 0.03 0.034 0.047 0.016 0.023
Different letter(s) within each column refer to significant differences according to
Fischer’s LSD mean separation test at P≤0.05
In addition to the potential yield advantages, narrow-row spacings can have a significant
impact on weed populations and on their approach to weed management. From a weed
management standpoint, perhaps the greatest influence that narrow row spacing has in
green pepper is in the reduction of the amount of light that reaches the soil surface and in
the amount of time that it takes for the crop to reach full canopy closure. Puricelli et al.
(2003) and Steckel and Sprague (2004) have each detected significantly less radiation at
the soil surface in narrow- compared to wide-row soybean throughout most of the growing
season. The reduction in light penetration and time to canopy closure has a profound
influence on the likelihood of weed emergence later in the growing season, a phenomenon
which Yelverton and Coble (1991) first termed "weed resurgence."
4.1.4 Weed dry biomass
Significant differences (P≤0.05) between weed dry biomass in the row spacing treatments
were found at all the sampling stages during both seasons except during the long rains
seasons at 6 WAT (weeks after transplanting) as shown in Table 4.2 in both varieties of
39
green pepper. The widest spacing showed significantly higher dry weed biomass
throughout the sampled development stages. At 8 WAT the 40 cm and 30 cm row spacings
were significantly different from each other with a difference of 19 g/m2 and 13 g/m
2 for
the long and short rains seasons respectively.
Table 4.2 Dry weed biomass (g) per quadrat during the long and short rainy seasons of
2015 at Alupe under different plant spacing (cm) at 4, 6 and 8 WAT (Weeks after
transplanting)
4 WAT 6 WAT 8 WAT
Long
Rains
Short
Rains
Long
Rains
Short
Rains
Long
Rains
Short
Rains
30*40 207c 340b 181a 129c 90b 74b
40*40 224b 473a 195a 148b 109b 87b
50*40 319a 505a 206a 198a 151a 128a
P-Value 0.014 0.043 0.132 0.037 0.05 0.01
Different letters within each column refer to significant differences according to Fischer’s
LSD mean separation test at P≤0.05
Decreasing plant spacing within rows significantly reduced weed dry weight and the
interaction of row and plant spacings with weed dry weight was significant due to the
increased intraspecific competition for water, nutrients, and light. A review of row spacing
experiments where an initial weed management practice had been accomplished revealed
that in 64% of the cases (72 of 113 site-years), less late-season weed density and/or
biomass, or greater late-season weed control was achieved in narrow- compared to wide
row soybean production systems (Yelverton and Coble, 1991).
40
4.2 Influence of row spacing on growth and yield of green pepper
4.2.1 Plant height
Significant differences (P≤0.05) were observed on the row spacing treatments during the
short rainy season at four weeks after transplanting (4 WAT) while no significant
differences were observed at the other stages of sampling for both seasons as shown in Fig.
4.3. The narrow spacing (30×40 cm) elicited the tallest plants (7.48 cm) as compared to
shorter plants of 6.70 cm and 6.82 cm in the 40×40 cm and 50×40 cm treatments
respectively.
Figure 4.3 Plant height of green pepper during the long and short seasons at Alupe in 2015
at 2, 4, 6 and 8 WAT (Weeks after Transplanting) under different row spacing treatments
(cm)
This increase in plant height in closer spacing might be because of the fact that in case of
higher population density, penetration of light was decreased which might have led to
increase the endogenous auxin formation and enhanced the growth of the buds which due
41
to competition tended to grow faster in order to outperform the neighboring plant. These
results agree with the findings by Decoteau and Graham (1994) who reported that plant
height and width decreased as in-row spacing increased. Similarly, increased weed
incidences where the row spacing in between plants increases due to high competition for
essential nutrients, sunlight and moisture therefore plants became taller in such competitive
environments. The results of the present study are in agreement with the findings of Maya
et al. (1997) who stated that, plant height of green pepper was significantly increased with
close spacing. Viloria et al. (1998) and Manchanda et al. (1988) also expressed similar
opinion on plant height of green pepper. The results of the present study for this character
are also in agreement with the findings of Maya et al. (1997b) who stated that, plant height
of green pepper was significantly increased with close spacing. The findings where there
were no significant differences between the row spacings on the plant height at the various
sampling stages is not consistent with the findings by Nyambi et al. (2004) who reported
that plant distance had no significant effect on plant height..
4.2.2 Number of leaves
A significant variation (P≤0.05) in the number of leaves per plant was observed due to
plant spacing (Fig. 4.4). The maximum number of leaves per plant (86.4) was recorded
from 40×40 cm spacing. The minimum number of leaves per plant of green pepper was
recorded from the closest spacing (30×40 cm) which was however statistically similar to
the widest spacing (50×40 cm).
42
Figure 4.4 Average number of leaves per plant during the long (a) and short rainy (b)
seasons of 2015 at Alupe under different plant spacing treatments (cm) at 4, 8 and 12 WAT
(Weeks after transplanting)
The measurements made on plant components show that more leaves were observed as
plant population reduced probably in relation to lower competition for physical production
resources (soil moisture and nutrients) which would enhance nutrient availability and
43
efficient utilization of assimilates. The number of leaves and leaf area plant-1
were
significantly different (P≤0.05) suggesting that plant density affected leaf formation and
development in response to competition for available space for nutrient absorption which
would influence plant vegetative growth and development. Since the distance between
individual plants was reduced with the increase in population, intra-specific competition
was higher and led to smaller sizes of individual plants in terms of number of leaves,
branches and leaf area plant-1
. A greater leaf area plant-1
due to increase in number and
mass of leaves means a higher specific leaf area which was supported by greater
investment in the stem. The number of leaves/plant was positively correlated with the
number of shoot(s)/plant. Limiting shoot number/plant, while proportionally increasing
plant population resulted in more effective coverage of soil by the canopy. The
transmittance of photosynthetically active radiation in the plant profile was more beneficial
with plants at a wider spacing, but with a higher number of shoots/plant. Similar findings
were reported by Cebula et al. (1995) on Capsicum annuum plants (vb. Bendigo FL) in
greenhouse conditions.
4.2.3 Number of branches per plant
The number of branches per plant differed significantly (P≤0.05) among the different
spacing levels where in the earlier weeks the narrow spacing (30×40 cm) showed the
highest number of branches per plant but after 8 weeks from transplanting, the wider
spacings showed significantly higher average branches per plant. The maximum average
number of branches (5.87) per plant was recorded from plants on the widest spacing
(50×40 cm) while the lowest number of branches in a plant (4.42) was recorded from the
closest spacing (30×40 cm) as shown in Fig. 4.5.
44
Figure 4.5 Influence of plant spacing (cm) on the number of branches per plant during the
long and short rainy seasons of 2015 at Alupe at 4, 6, 8, 10 and 12 WAT (WAT-Weeks
after transplanting
The higher number of branches per plant in the wider row spacing might be that the plants
of wider spacing received more light, nutrients and other resources than the plants of close
spacing due to lower competition from the nearest plant. The results of the present study
for this character is in agreement with the findings of Ravanappa et al. (1998a) who
reported that the lowest plant density treatment obtained from the widest spacing (75x60
cm) produced the highest number of branches per plant.
4.2.4 Fruit mass
The yield per plant was significantly influenced (P≤0.05) by spacing levels as shown in
Fig. 4.6. The maximum yield of 551.8 g and 555.1 g for the long and short rainy seasons
respectively, was recorded from the 40×40 cm plant spacing and differed significantly
from that of the other spacings. The lowest yield per plant was obtained from the widest
spacing (50×40 cm) for both seasons. The medium spacing (40×40 cm) facilitated the
45
plants to develop properly with less inter and intra plant competition for utilizing the
available resources resulting higher yield per plant compared to the closest spacing (30×40
cm).
Figure 4.6 Average yield per plant (g) of green pepper at different row spacing (cm) during
the long and short rainy seasons at Alupe in 2015
As plant densities declined, reduction in the number of plants per unit area is partially
compensated by an accompanying increase in the productivity of each plant. Zhang et al.
(1992), also reported similar results for oilseed rape. These results are in agreement with
those of Lorenzo and Castilla (1995) who reported that marketable green pepper yield were
significantly higher under a high plant population (3.2 plants m-2
) than under a low plant
population (2 plants m-2
). They concluded that a high leaf area index (LAI) 45 for a high
plant population resulted in improved light interception which then led to higher biomass
and yield than under a low plant population. Despite using higher plant populations,
Agarwal et al. (2007) also reported that green pepper marketable fruit yield increased as
46
plant population increased from 50 000 to 200 000 plants ha-1
and slightly decreased with a
further increase in plant population under greenhouse conditions. The increase in fruit
mass per hectare was as a result of an increased plant population to a threshold level maybe
attributed to better utilization of available light and nutrients. On the other hand, in higher
population density reduced yield per plant might be attributed to lesser fruit yield per plant.
The result of the present experiment is in agreement with the findings of Ravanappa et al.
(1998), who also obtained the highest yield with the lowest plant density treatment. The
result is in agreement with that of Verheij and Verwer (1973) who reported that the
individual fruit weight declined with increased plant density. Though fruits/plant were
higher in the widest spacing (50×40 cm), the reduced average yield per plant was due to
higher plants/m2 in the 40×40 cm treatment which resulted in higher yield while the lowest
yield per plant in the narrow spacing (30×40 cm) might be due to the reduced individual
fruit weight. Russo (2003), Nasto et al. (2009) and Khasmakhi-Sabet et al. (2009) had
observed that the highest fruit yield of pepper was obtained when grown at the higher
population densities.
4.2.5 Fruit length and breadth
A non-significant variation in the length of fruits of green pepper was observed due to
different plant spacing treatments (Table 4.3). There were no significant differences
between the two varieties during both seasons on the fruit breadth (Appendix 3) and length
(Appendix 4). The result on the fruit length agrees with those by Kim et al. (1999) who
stated that planting systems and distances did not significantly alter plant height, main
stem length, fruit length, fruit diameter or thickness of pericarp. The spacing levels varied
significantly in respect of the fruit breadth for both seasons (Table 4.3). The highest fruit
47
breadth (4.37 cm) was obtained in plants of 40×40 cm which was statistically similar to
that of 30×40 cm while the lowest fruit breadth was recorded in the closest spacing. The
result on the fruit length is in disagreement with the report of Manchanda et al. (1988) who
reported that the fruit breadth of green pepper increased with decreasing plant density.
Table 4.3 Fruit length, fruit breadth and number of fruits per plant during the long and
short rainy seasons at Alupe under different plant spacings (cm) in 2015
Spacing
Treatments
(cm)
Fruit Length (cm) Fruit Breadth (cm) Fruits per Plant
Long Short Long Short Long Short
30*40 2.029a 3.342
a 2.504
b 3.32
c 3.65
c 4.17
a
40*40 2.483a 3.413
a 2.883
a 4.37
a 4.06
b 4.47
a
50*40 2.217a 3.284
a 2.663
b 3.84
b 4.59
a 4.74
a
P-Value 0.124 0.075 0.038 0.007 0.025 0.089
Different letter(s) within each column refer to significant differences according to
Fischer’s LSD mean separation test at P≤0.05
4.2.6 Number of fruits per plant
Among the yield contributing characters, number of fruits per plant is one of the important
traits (Table 4.3). The number of fruits per plant showed significant differences during the
long rainy season due to plant spacing where the highest average number of fruits (4.59)
per plant was recorded from the widest spacing (50×40 cm) which was significantly higher
than those of other spacings (Table 4.3). The varieties did not differ significantly during
both seasons on the number of fruits per plant (Appendix 5). Reduced number of plants
under wider spacing had less inter or intra plant competition which caused an increased
number of fruits per plant. The results are in agreement with the report of Mishriky and
48
Alphonse (1994) who stated that the number of fruits per plant decreased with closer plant
spacing.
4.3 Effect of mulching materials on weed control in green pepper
4.3.1 Number of weed species
Significant differences (P≤0.05) were observed between the mulch treatments on the
number of weed species per plot in all the weeding regimes for both seasons. The number
of weed species was highest in the control for both seasons during all the sampling stages
(Fig. 4.7).
Figure 4.7Number of weed species m2 during the long rain season of March – August (a)
and short rain season of September - December (b) at Busia in 2015 as influenced by
different mulching materials
It is well established that a kilogram of weed biomass in a field corresponds to the loss of a
kilogram of a given yield of crop (Rao, 2000). The weed species reduced as the crop
growth advanced from four weeks to eight weeks after transplanting. Marana et al. (1986)
also estimated that the critical period of weed competition to be 30-40 days after seeding;
therefore, they suggested that weeds should be removed for 40-50 days after sowing and
49
similar findings were shown in the current study. The above authors further emphasized
that the presence of weeds reduced fruit yield by 70% subject to the stage and duration of
competition. Shadbolt and Holm (1956) also concluded from their studies that the first four
weeks were critical in many vegetable crops, during which time weeds should be removed.
The lowest number of weed species was observed on the plastic mulches for the two
seasons. The weed species observed were Tradescantia fluminensis, Galinsoga parviflora,
Oxalis latifolia, Amaranthus spp, Tagetes minuta and Bidens pilosa. During the short rain
season, the control plots showed a maximum of 8 weed species in an area of 1 m2.
Therefore, this indicates that the competitiveness of green pepper with weeds can be
improved through the use of black plastic polythene as mulch. The reduced number of
weed species on black plastic led to enhancement of the subsequent yield, indicating that
the weeds were effectively controlled through shadowing of the covered weeds restricting
them from performing photosynthesis that reduced their competitiveness. The black plastic
not only physically barred the perennial weeds from emerging and growing but also the
underground propagules were suffocated because of increased temperature and reduced
light availability. It has been reported that yield losses in crops occur due to biomass and
density of weeds (Mamolos and Kalburtji, 2001).
4.3.2 Weed vigor
The weed vigor was greatest on the control treatment for both seasons at four weeks after
transplanting and closely followed by straw mulch treatment (Table 4.4). The least weed
vigor was observed in plastic treatments with the black showing the poorest growth of
weeds. The same trend was observed at eight weeks after transplanting. The use of mulch
50
has been reported to enhance microbial activity in soil by improving soil agro-physical
properties and therefore suppressing weed growth (Iruthayaraj et al., 1989).
Table 4.4 Mulching materials influence on the weed vigor during the long rains of March –
August and short rains of September - December 2015 at Busia
Mulch
Treatment
Weed Vigor 4 WAT Weed Vigor 6 WAT Weed Vigor 8 WAT
Long Rain
Short
Rain
Long
Rain
Short
Rain
Long
Rain
Short
Rain
Control 1.389a 1.278
a 1.444
a 1.167
a 1.444
a 1.556
a
Straw 1.889b 1.444
b 1.667
ab 1.611
b 1.778
b 1.694
b
Black 2.889d 2.889
c 1.944
b 2.671
c 2.667
d 2.056
d
Transparent 2.056c 2.111
c 1.722
ab 1.765
b 2.111
c 1.889
c
P Value
<0.001 <0.001 0.048 <0.001 <0.001 0.004
Different letters within each column refer to significant differences according to Fischer’s
LSD mean separation test at P≤0.05, WAT-Weeks after transplanting
All the stages for both seasons showed significant differences between the mulch
treatments on weed vigor score. The black plastic polythene was more effective in
increasing crop yield compared to other mulching materials, indicating that weeds were
better controlled through covering of weeds by the mulch’s shadow disabling them from
executing photosynthesis thus reducing greatly their competitiveness with green pepper
crop. These findings conform to earlier reports of black plastic polythene mulch in weed
control by Hartmann et al. (1981) and Olabode et al. (2006) where the latter worked on
Okra plants. Govindra et al. (1986) observed that weeds caused a 57% reduction in tomato
yield when compared with weed free conditions. Adigun (2002) also reported that
uncontrolled weed growth during the crop life cycle resulted in 92 to 95% decline in
tomato fruit yield.
51
4.3.3 Fresh weed biomass
The control plots had the highest weed fresh biomass in all the sampling stages for both
seasons (Fig. 4.8). The highest biomass was recorded at four weeks after transplanting on
the control plot with a mean of 1629 g/m2. The black plastic had the lowest fresh biomass
of weeds for both seasons in the three sampling periods. The transparent plastic was the
second most efficient material in the suppression of weeds growth.
Figure 4.8 Aboveground fresh weed biomass (m2) during the long raining season of March
– August and short raining season of September - December 2015 at Alupe under different
mulching materials
Black plastic mulch effectively reduced weed growth by intercepting nearly all-incoming
radiation. It has been found that it is essential to cover the soil surface with different
materials to attain high biological activity, preserve soil moisture and to achieve a good
control of weeds under the black plastic whereas clear mulch absorbs only 5% of short-
wave radiation, reflects 11%, but transmits 84% of it (Aman and Rab, 2013). Only during
the long rains season on the first stage of weeding showed indicate insignificant influence
52
of the mulch treatments on the weed fresh biomass in both green pepper varieties. The
transparent polythene mulch had the highest fresh weed biomass during the second
weeding while the organic mulch showed the greatest mass of fresh weeds per plot during
the last period of weeding. Yield losses in crops have been reported to occur due to
accumulation of weed biomass and weeds density (Mamolos and Kalburtji, 2001; Aman
and Rab, 2013).
4.3.4 Dry weed biomass
All the weeding stages showed significant differences (P≤0.05) of mulch treatments on the
dry biomass of weeds for both seasons (Fig. 4.9). The control had the highest dry biomass
while the straw mulch had the second highest dry weed biomass. The weeds lost more than
60% mass after drying where black plastic mulch had the lowest dry biomass at all the
weeks of sampling followed by transparent plastic mulch.
Figure 4.9 Aboveground dry weed biomass during the long rains of March - August and
short raining season of September – December 2015 at Alupe under different mulching
materials
53
By providing a physical barrier, mulching reduced the germination, growth and
development of weeds. Pimpini (1974) established that plastic mulches benefitted crops
with black and photo selective plastic being preferable to the transparent type in eggplant
for weed control. The mulches favored the reduction of evaporation which led to higher
soil moisture content, reduced weed growth and the decomposition of added mulches
might also have contributed to increase in supply of nutrients and moisture for the overall
increase in crop yield. Layering or mulching soil surface prevented weed seed germination
and physically suppressed seedling emergence. In another study by Ossom et al. (2003), it
was reported that white and green covering had little effect on weeds, whereas brown,
black, blue or white on black films significantly reduced emergence of weeds. Daisley et
al. (1988) also observed significant differences in weed control between mulched and
unmulched plots of eggplant, cowpea and sweet potato.
4.4 Effect of mulching materials on growth and yield of green pepper
4.4.1 Seedling vigor
Significant differences at (P≤0.05) were observed between mulching materials on seedling
vigor for both seasons where green peppers in the straw mulch had the greatest growth
vigor compared to the other treatments (Fig. 4.10). During the long rain season the green
pepper varieties in the black polythene had similar seedling growth vigor as the plants in
the straw mulch. In both seasons the unmulched treatment had poor growth compared to
the mulched treatments. This was due to the mulches’ high rate of moisture preservation
and reduced transpiration rates by the plants in the mulched plots. Soil mulching also
improved the micro-climate at the vicinity of the plants which facilitated plant growth.
This has been reported in other studies where it was found that young green pepper
54
seedlings cannot withstand either water deficit or excess soil moisture while older plants
will be sensitive to moisture balances at crucial stages of flowering and fruiting (Gonzalez
and Matheus, 2001).
Figure 4.10 Influence of mulching materials on seedling vigor of green pepper during the
short rain season of September – December 2015 (A) and long rain season of March –
August 2015 (B) at Alupe, Busia
The conservation of soil moisture may help in preventing the loss of water through
evaporation from the soil facilitating maximum utilization of moisture by the plants.
Therefore this study reveals that mulching with plastic is a method by which soil moisture
can be conserved (Sandal and Acharya, 1997).
4.4.2 Plant height
The shortest plants were observed in control plots at all the growth stages while the
mulched plots showed significantly taller plants (Fig. 4.11). There was a linear increase in
all the treatments with the control lagging until 10 weeks after transplanting (10 WAT)
where the black polythene treatment consistently produced the tallest plants of both
California Wonder and Yolo Wonder varieties.
55
Figure 4.11 Influence of mulching materials on the plant height of capsicum in the short
rains of September – December 2015 (a) and long rains of March – August 2015 (b) at
Alupe
The increased plant height in mulched plants was possibly due to better availability of soil
moisture and optimum soil temperature provided by the mulches. Changes in the plant
height of green pepper have been observed by using different mulches and plastic mulch
increased the plant height more than other mulches (Shinde et al., 1999).
4.4.3 Number of leaves
The maximum number of leaves per plant was found on the plants mulched with
transparent and black plastic polythene mulches at all growth stages but with significant
differences between treatments only observed at week 8 and 10 after transplanting (Fig.
4.12). The transparent mulch had the highest number of leaves per plant at ten weeks after
transplanting (10 WAT) with a mean of 56 leaves per plant. There were no significant
differences between the varieties on the average number of leaves per plant as shown in
Appendix 6.
56
Figure 4.12 Number of leaves per plant among mulching treatments at Alupe during the
short rainy season (September – December 2015) and long rainy season (March – August
2015)
The black polythene and transparent plastic were effective in weed control therefore
enabling the plant to produce more leaves compared to the control. The microclimatic
condition which was improved by the mulches might have provided a suitable habitat for
producing higher number of leaves by the plants. Similar findings were observed in
another study where the effectiveness of plastic mulches for the production of leaves in
maize was better than the control (Izakovic, 1989).
4.4.4 Number of branches
Mulch treatments significantly influenced (P≤0.05) the number of branches in both seasons
from week two after transplanting to week eight after transplanting with a linear increase in
all treatments (Fig. 4.13) in both green pepper varieties. The straw mulch showed the least
number of branches per plant and stagnated at week six while the other materials and the
57
control continued to increase especially in the long rain season. The transparent mulch had
the highest number of branches per plant for both seasons.
Figure 4.13 Effect of mulching materials on the number of branches per plant during the
short rain season of September – December 2015 (a) and long rain season of March –
August 2015 (b) at Alupe, Busia County
All the mulches had a positive effect on generating and retaining a higher number of
branches per plant. Favorable weather condition and moisture of the soil are important
parameters affecting the number of branches per plant. It was reported that mulched tomato
plants had more branches than that of unmulched plants (Srivastava et al., 1994), which
agrees with the present results.
4.4.6 Stem girth
Mulched plants had significantly higher base diameter than those in controls at all growth
stages for both seasons, followed by the control which had the least (Fig. 4.14). The plant
without mulch had the smallest base diameter at all growth stages. According to Decoteau
(2008) in red bell pepper, plants grown in red mulch were wider than the other colored
58
mulch treatments. Mulch color effects on internodes length suggested a role for surface
reflected light on pepper plant development.
Figure 4.14 Influence of mulching materials on the plant height of capsicum in the short
rains of September – December 2015 (a) and long rain season of March – August 2015 (b)
at Alupe in Busia County
The plants in the unmulched plots (control) had narrow girths at all growth stages. This
result was in conformity with the report of Easson and Fearnehough (2000) on maize.
Similar result was also reported by Chancellor (1977) who found that mulch had a
significant effect on total chlorophyll content in green pepper under black plastic mulch
showed the greatest total chlorophyll content among the mulches thereby enhancing plant
heights positively. Less moisture depletion under the mulches was a result of prevention
of contact between the soil and dry air, which reduce water loss into the atmosphere
through evaporation. Also, mulches reduce impact of raindrops and splash, thereby
preventing soil compaction, reducing surface run-off and increasing water infiltration
(Ravinder, 1997). All these combined to increase the soil moisture content and reduce
moisture depletion. As moisture depletion is least under the plastic mulches so the rate of
59
moisture recharging ability would be least because water infiltration will be prevented.
None the less, capillary movement of water molecules through the soil pores from the
water table will supply water to the root zone of the crop grown under plastic mulch
(Hochmuth, 2001).
4.4.7 Fruit mass
The effect of different plastic mulches on fruit mass per plant was significant at P≤0.05
(Fig. 4.15) for both varieties. The black plastic polythene mulch had the heaviest fruits
(924.5 and 649.8 g/plant) which was however insignificantly different from the other
mulched plots for both seasons as shown in Fig. 4.15. The transparent mulch had the
second heaviest fruits followed by the straw mulch with 890.5 and 649.8 g/plant,
transparent mulch with 858.7 and 635.5 g/plant during the long and short rain seasons
respectively.
Figure 4.15 Total fruit mass as influenced by mulching materials in two seasons of 2015 at
Alupe in Busia County
60
Ravinder et al. (1997) reported that mulching significantly improved the number of fruits
per plant thus the mass and reduced the percentage of fruit abortion compared to
unmulched control, as found in the present experiment. Further, Ravinder et al. (1997)
observed that the plants in the black plastic mulch produced the highest fruit mass per plant
(533.4 g) and per hectare (21.3 t), followed by blue and transparent plastic mulches.
Control plot showed the lowest fruit yield both in per plant (336.3 g) and per unit area
(13.45 t/ha-1
).
Fruit yield increased in mulched plot because of increased number of fruits per plant.
These results coincide with those of Siborlabane (2000), who pointed out that the yield and
quality of the fruit for the fresh tomato market varies according to the type of mulch used
on the plantation. The increase in the number of fruits per plant of mulched plot was
probably associated with the conservation of moisture and improved microclimate both
beneath and above the soil surface. The suitable condition enhanced plant growth and
development and produced increased fruit bearing nodes compared to the control.
Considering the relationship between the soil moisture content and fruit number, it was
clear that fruit number was strongly related with soil moisture content. Olarewaju and
Showemino (2006) observed the increase in biological activities in the soil to influence
nutrient availability and subsequently the fertility of such soils.
4.4.8 Number of seeds per fruit
The transparent mulch resulted in the highest number of seeds per fruit while the control
had the lowest during the long and short rain seasons (Fig. 4.16). The differences were
however not significant among the mulched treatments and between varieties for both
seasons. Bosland and Votava (2000), showed that in some cultivars of Chili seed can
61
contain up to 60% of the dry weight of the fruit which makes it an important economic part
of the crop.
Figure 4.16 Average number of seeds per fruit for the long rains of March – August 2015
and short rains of September – December 2015 at Alupe in Busia County
4.4.9 Fruit length and breadth
Fruit length and breadth was significantly different (P≤0.05) between all the treatments as
compared to the control for both seasons (Fig. 4.17). The mulched plots had a greater fruit
diameter and length with a maximum of 7.8 cm on the black polythene treatment for length
and 5.5 cm on the straw mulch for fruit diameter. California Wonder variety and Yolo
Wonder variety showed no significant differences on the fruit diameter and length in both
seasons as shown in Appendix 3 and 4 respectively.
62
Figure 4.17 Fruit length (a) and breadth (b) of green pepper as influenced by different
mulching materials in the long rains of March – August 2015 and short rain season of
September – December 2015 at Alupe in Busia County
The increase in fruit length may be due to the varying moisture regimes in the soil for the
different mulching materials used. It is likely that the black polythene, transparent
polythene and straw mulches conserved more moisture due to lower evaporative losses
than the unmulched plots. Alabi (2006) reported that increase in the number of leaves
would increase photosynthetic surfaces and the current photosynthates produced would
enhance the physiological activities leading to production of more assimilates used to
significantly increase fruit production, fruit sizes and fruit diameter. Larger and wider hot
63
pepper pods are considered to be the best in quality and are more in demand for fresh as
well as dry pod use in markets (Beyene and David, 2007). Therefore, subjectively, this
quality attribute, along with pod length and pericarp thickness, could be preferred by
consumers over thinner and shorter pods.
4.4. Correlation Analysis for variables
Correlation studies on various agronomic traits of plants aid in developing criteria for
selection of the desired traits in crop improvement programmes. The relative magnitude of
the association between yield of a crop and various traits helps in screening traits used in
constructing an indirect selection index for the yield (Singh, 1992). Relationships of
different agronomic traits with yield and its components are basic needs for carrying out
any crop improvement; such information is scanty for green pepper. There were strong
positive correlations that were significant in both seasons between variates. The number of
branches were highly and significantly (P<0.001) correlated to the fruit diameter (r=0.513)
during the long rains season. The same trend was observed during the short rainy season
(r=0.596). Similar findings have been reported by Kamruzzahan (2000) in tomatoes.
Branching is essential in fruiting for legumes as compared to green pepper ensures a higher
fruiting and their quality is enhanced with an even increased branching that ensures higher
metabolism, transport, supply and support to the reproductive regions. Branching is an
indication of better plant nutrition which in turn enhances other parts development and
yield. Yield had been found to be positively and significantly correlated with number of
fruits, fruit mass and fruit diameter (Khatun et al., 1999). Branching directly and positively
influenced the fruit fresh weight (r=0.413) during the long rainy season. A higher number
of branches hold more fruits that always directly lead to increased produce unless the
64
quality is compromised. The height of green pepper and number of branches were
significantly and positively correlated (r=0.636) during the long rains season. The vigorous
growth of the crop due to optimal conditions models increase in branching. Therefore, the
plants metabolic activity will initiate more branches that support the plants. The number of
leaves and branching showed significant and direct relationship where an increase in one
enhanced the other for both seasons. During the long rains a correlation coefficient value
of r=0.701 was observed while a value of r=0.646 was observed during the short rainy
season. The increase in number of leaves provided greater photosynthetic area thus
facilitating increased energy cycle that increased branching of the plants.
The stem girth and number of branches per plant were significantly and positively
correlated. This was observed for both seasons where the long rainy season had a
coefficient value of r=0.606 and the short rainy season showed a marginally lower value of
r=0.577. These results support the idea that the fruit length and stem thickness of plants of
the red pepper genotypes are important factors, as they are the primary determinant for
fruit numbers per plant (Depeste, 1987; Silvetti, 1991; Sreelathakumary and Rajamony,
2004). The number of fruits per plant directly correlated with the fruit diameter positively
for both seasons for both seasons, (r=0.783) for the long rains and (r=0.797) for the short
rains. This greatly signifies the quality of fruits is an important aspect in modelling or
determining the number of harvestable fruits in a given field area. Better plant nutrition
and agronomic management greatly impacts on the production of fruits by improving their
quality. The fruit diameter was also highly and positively influenced by the plants height
(r=0.518) which probably enhanced metabolism and transport of minerals through the
plants.
65
The height was also directly impacted on the number of flowers per plant (r=0.573) during
the short rains season. Rani et al. (2008) found that in tomato, the yield contributing traits
are plant height and fruit mass. Increased plant height accelerated flowering due to greater
metabolic activity by the crop. An increase in the number of flowers per plant positively
correlated with the length of the fruits (r=0.516) during the long rains season where the
greater number of flowers does assume higher number and quality of fruits if conditions
are conducive. Solanki et al. (1986) and Basavaraj (1997) have reported that fruit length,
fruit width, number of fruits per plant and total fruit mass have strong positive correlations
with yield. The number of seeds (r=0.775) during the short rains, number of fruits per plot
(r=0.693) during the long rains and number of fruits per plant (r=0.886) were directly and
significantly correlated to the fruit length. Islam and Khan (1991) also reported that fruit
yield was significantly correlated with the fruit length in a study on tomatoes. The number
of seeds were positively correlated to the fruit length (r=0.775) during the short rains
season. The plant height and the number of flowers were directly correlated (r=0.637)
during the same period and number of leaves and the stem girth (r=0.877). Sharma (1990)
reported that plant height had the direct effect on number of flowers which affected the
fruit yield. This was highly significant because the stem provides a passage of nutrients
through the xylem up to the leaves which are processed through photosynthesis and then
brought down to the stems and further down to the roots. The number of leaves greatly
influenced directly the fresh weight of fruits (r=0.569) during the short rains. Leaves are
important components of plants energy provision that in turn enhances fruiting.
66
CHAPER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.0 CONCLUSION
Reducing row spacing in green pepper is more likely to reduce weed resurgence in
green pepper. This response is directly correlated with the faster rate of canopy
closure and reduction in light interception at the soil surface in narrow- compared
to wide-row systems. The available information also shows that the critical time of
weed removal is most likely to occur later in narrow- compared to wide-row
spacing in green pepper.
The lower plant population densities produced more vigorous crops than at higher
population densities but this could not compensate for the small number of plants
per unit area.
Synthetic mulches, especially black plastic film, effectively suppressed most weeds
growth, thereby reducing labor and other costs for weed control. The opaque film
reduced germination of light-responsive weed seeds; shaded out and physically
blocked the emergence of most weeds; and can enhance crop growth by reducing
competition, conserving soil moisture, promoting soil warming, and speeding
nutrient mineralization from soil organic matter.
Based on the experimental results, the plastic mulches had significantly positive
effects on the growth, and yield of green pepper, and black plastic showed superior
performance among the plastic mulches in the study area.
67
5.1 RECOMMENDATIONS
Narrow row spacing of 30×40 cm is recommended in green pepper production
because it leads to higher weed control and greater weed growth suppression.
The 40x40 cm row spacing was found to be the best for production of green pepper
in Busia County conditions and is therefore highly recommended.
The black plastic mulch is recommended for weed control in green pepper.
The black polythene mulch is recommended to be used in growing green pepper in
the study area for better conservation of soil moisture and nutrients for good crop
growth and higher yield.
68
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7.0 APPENDICES
Appendix 1. Pearson’s correlation on selected parameters in green pepper during the long rainy season
1 -
2 0.285** -
3 0.2781 0.1431 -
4 0.2197 -0.0072 0.2447 0.1707 -
5 0.6804* 0.1964 0.309 0.2594 0.3303* -
6 0.7203 0.2464 0.37 0.305 0.054 0.5812 -
7 0.3308 -0.0154 0.533 0.5679 0.5941 0.3975 0.2654 -
8 0.7218* 0.2554 0.3847 0.3118 0.0129 0.5487** 0.7842 0.2366 -
9 -0.094 0.1418 0.0188 -0.0706 -0.067 -0.1257 -0.0368 -0.0406 -0.118 -
10 -0.1155 -0.0822 -0.1465 -0.062 -0.2365 -0.0963 -0.025 -0.1871 -0.0223 0.1207 -
1 2 3 4 5 6 7 8 9 10
1-Branches, 2-Flowers per plant, 3-Fruit length, 4-Fruit mass, 5-Height, 6-Number of leaves, 7-Seeds per fruit, 8-Stem girth, 9-Weed
Fresh weight, 10-Weed species
83
Appendix 2. Pearson’s correlation on selected parameters in green pepper during the short rainy season
1 -
2 0.1622** -
3 0.0011 0.4013 -
4 0.1009 0.2565 0.1507 -
5 0.0715 0.5085 0.8152* 0.0989 -
6 0.1548 0.1142 0.0545 0.5906 0.0581 -
7 0.3405 0.0404 0.07 0.0715 0.0947 -0.0314 -
8 0.5848* 0.0738 -0.1828 0.2525
-
0.0629 0.2878 0.2692 -
9 0.094 0.281 0.1422 0.7746 0.0936 0.6258** 0.0136 0.1629 -
10 0.076 0.151 0.1061 0.2742 0.2445 0.3579 0.5004* 0.272 0.2701 -
11 -0.3708 0.0566 0.2944
-
0.0363 0.1712 -0.2259 -0.2494
-
0.5862 0.0452
-
0.2373 -
12 -0.0775
-
0.2437 0.0004
-
0.2009 0.0406 -0.1519 0.0982
-
0.0609 -0.214 0.0827 0.0956 -
13 0.035
-
0.1042 -0.0651
-
0.3114 0.0646 -0.2926 -0.0522
-
0.0074
-
0.3057
-
0.0327 0.0618 0.6818 -
14 1 2 3 4 5 6 7 8 9 10 11 12 13
1-Branches, 2- Fruit diameter, 3- Flowers plant, 4- Fruit length, 5- Fruit per plant, 6- Fruit mass, 7- Height, 8- No of leaves, 9- Seeds
per fruit, 10- Stem girth, 11- Vigor, 12- Weed Dry weight, 13- Weed species
84
Appendix 3. The interaction effect between variety, mulching and row spacing on the fruit diameter during the long rains seasons
California Wonder Black Plastic 30by40cm 2.87 Yolo Wonder Black Plastic 30by40cm 3.33
40by40cm 5.03
40by40cm 1.45
50by40cm 2.12
50by40cm 5.07
Control 30by40cm 4.67
Control 30by40cm 3.33
40by40cm 2.5
40by40cm 3.33
50by40cm 1
50by40cm 2.33
Straw Mulch 30by40cm 1.75
Straw Mulch 30by40cm 1.5
40by40cm 1.33
40by40cm 2.81
50by40cm 1.67
50by40cm 1.95
Transparent plastic 30by40cm 1.67
Transparent plastic 30by40cm 1.67
40by40cm 3.83
40by40cm 2.67
50by40cm 5
50by40cm 2
P-Value 0.019
L.S.D 3.62
85
Appendix 4. The interaction effect between variety, mulching and row spacing on the fruit length during the long rains season
California Wonder Black Plastic 30by40cm 3.1 Yolo Wonder Black Plastic 30by40cm 4.33
40by40cm 7.5
40by40cm 1.21
50by40cm 1.54
50by40cm 4.83
Control 30by40cm 2.23
Control 30by40cm 4
40by40cm 3.83
40by40cm 4.83
50by40cm 2
50by40cm 4.17
Straw Mulch 30by40cm 2.1
Straw Mulch 30by40cm 2.33
40by40cm 1.73
40by40cm 1.85
50by40cm 1.93
50by40cm 3.24
Transparent plastic 30by40cm 2.1
Transparent plastic 30by40cm 2.5
40by40cm 4
40by40cm 3.67
50by40cm 5.8
50by40cm 2.17
P-Value 0.036
L.S.D 3.62
86
Appendix 5. The interaction effect between variety, mulching and row spacing on the average number of fruits per plant during
harvesting one of the long rains season
California Wonder Black Plastic 30by40cm 1.67 Yolo Wonder Black Plastic 30by40cm 1
40by40cm 2.33 40by40cm 1
50by40cm 1.42 50by40cm 2
Control 30by40cm 2.33 Control 30by40cm 1
40by40cm 1 40by40cm 1.33
50by40cm 1.33 50by40cm 1.67
Straw Mulch 30by40cm 1 Straw Mulch 30by40cm 1.67
40by40cm 1.33 40by40cm 1
50by40cm 1 50by40cm 1
Transparent plastic 30by40cm 1.67 Transparent plastic 30by40cm 1.67
40by40cm 1.67 40by40cm 1.67
50by40cm 2 50by40cm 1.33
P-Value 0.003
L.S.D 1.535
87
Appendix 6. The interaction effect between variety, mulching and row spacing on the average number of leaves per plant during the
long rains season
California Wonder Black Plastic 30by40cm 71 Yolo Wonder Black Plastic 30by40cm 81.4
40by40cm 104
40by40cm 79.5
50by40cm 69
50by40cm 86.4
Control 30by40cm 89.5
Control 30by40cm 52.3
40by40cm 82.4
40by40cm 95.2
50by40cm 78.1
50by40cm 94.1
Straw Mulch 30by40cm 62.3
Straw Mulch 30by40cm 95
40by40cm 95
40by40cm 54.1
50by40cm 87.1
50by40cm 47.9
Transparent plastic 30by40cm 60.7
Transparent plastic 30by40cm 96.2
40by40cm 106.4
40by40cm 74.1
50by40cm 101.7
50by40cm 49.2
P-Value 0.003
L.S.D 47.07
88
Appendix 7. The interaction effect between variety, mulching and row spacing on the average number of seeds per fruit during the
long rains season
California Wonder Black Plastic 30by40cm 37 Yolo Wonder Black Plastic 30by40cm 148
40by40cm 189
40by40cm 44
50by40cm 51
50by40cm 208
Control 30by40cm 258
Control 30by40cm 80
40by40cm 96
40by40cm 235
50by40cm 107
50by40cm 38
Straw Mulch 30by40cm 87
Straw Mulch 30by40cm 81
40by40cm 149
40by40cm 62
50by40cm 63
50by40cm 12
Transparent plastic 30by40cm 52
Transparent plastic 30by40cm 291
40by40cm 211
40by40cm 135
50by40cm 103
50by40cm 98
P-Value 0.006
L.S.D 78.8
