A Review of Silicon in Soils and Plants and Its Role in US ...planttuff.com/wp-content/.../A_Review_of_Silicon_in... · Silicon in soils is grouped into liquid, adsorbed, and solid

TECHNICAL ARTICLE

A Review of Silicon in Soils and Plants and Its Role in USAgriculture History and Future Perspectives

Brenda S Tubana1 Tapasya Babu2 and Lawrence E Datnoff 3

Abstract Silicon (Si) is the second most abundant element in the earthrsquoscrust and plays a number of important roles in the mineral nutrition of plantsIn the past 20 years the scientific documentation on the benefits of Si tocrops has helped establish Si fertilization as an agronomic practice in manyagricultural lands worldwide However very little information has been con-solidated on the use of Si specifically for US agriculture Consequently theobjectives of this review are to provide (1) information on the dynamics ofSi in soil use and sources (2) a history and up-to-date documentation onSi-related research in many areas of US production agriculture and (3) per-spectives on Si as a plant beneficial nutrient and the potential of Si fertiliza-tion as an agronomic practice in US crop production systems The Si-drivenmechanisms enhancing the productivity of a wide array of crops understressed conditions are discussed in this review Based on the recent10-year average production level and published shoot Si content theprincipal crops grown in the United States can collectively take up955 million tons of Si annually whereas the annual Si removal rate forthe entire US cropland area is estimated at 211 million tons On the basisof this projected annual Si removal rate adoption of continuous intensivefarming systems in the country low solubility of soil Si and complexchemical dynamics of Si in soil increasing plant-available Si levelsthrough fertilization is therefore foreseen a logical agronomic practice forUS agriculture

KeyWordsCrop production fertilizer monosilicic acid nutrient siliconsoil fertility

(Soil Sci 2016181 00ndash00)

S ilicon (Si) is the second most abundant element in the earthrsquoscrust almost exclusively found in the form of silicon diox-

ide (SiO2) in association with a wide array of Si-bearing min-erals in crystalline poorly crystalline and amorphous phases(Sommer et al 2006) In the early 1900s Si was recognizedas one of the 15 elements needed for plant life (Halligan1912) However to date the essentiality of Si is only knownfor diatoms scouring rushes and other members of theyellow-brown or golden algae (Epstein 1999) Its essentialityfor higher plants remains questionable because of the lack of

1Soil Science School of Plant Environmental and Soil Sciences LouisianaState University Agricultural Center Baton Rouge LA2Soil Science Department of Soil and Crop Sciences Cornell UniversityIthaca NY3Plant Pathology Department of Plant Pathology and Crop Physiology LouisianaState University Agricultural Center Baton Rouge LAAddress for correspondence Brenda S Tubana PhD Soil Science School ofPlant Environmental and Soil Sciences Louisiana State University AgriculturalCenter 104SturgisHall BatonRougeLA70803E‐mail btubanaagcenterlsueduFinancial DisclosuresConflicts of Interest This review article was partiallyfunded by Edward C Levy Co Received 06-08-2016Received June 8 2016Accepted for publication September 18 2016Copyright copy 2016 Wolters Kluwer Health Inc All rights reserved This is anopen-access article distributed under the terms of the Creative Commons Attri-bution-Non Commercial-No Derivatives License 40 (CCBY-NC-ND)where it is permissible to download and share the work provided it is properlycited The work cannot be changed in any way or used commercially withoutpermission from the journalISSN 0038-075XDOI 101097SS0000000000000179

Soil Science bull Volume 181 Number 910 SeptemberOctober 2016

evidence showing Sirsquos direct role in plant metabolism and pro-duction of Si-bearing organic compounds (Ma et al 2001Knight and Kinrade 2001 Ma and Takahashi 2002Richmond and Sussman 2003) Nevertheless because of thelogically flawed definition of essentiality of nutrients (Epstein1999) Si being a major inorganic constituent in higher plantsand the significant amount of evidence showing the value of Siin improving crop productivity (Epstein 1994 Keeping et al2009 Meyer and Keeping 2005 Snyder et al 2007) the applica-tion of Si fertilizers today is very common in many crop produc-tion systems worldwide

The importance of Si as a nutrient in crop production isamong the most valued roles of Si to humans According toFAOSTAT (2014) the most produced crops in the world in 2012included grain crops (wheat Triticum aestivum and rice Oryzasativa) and sugarcane (Saccharum officinarum) (Fig 1) Basedon the estimated Si content of these crops (Hodson et al 2005)seven are classified as Si accumulatorsmdashplant species thataccumulate more than 10 Si on dry matter basis Crops canremove as much as 210 to 224 million tons Si per year worldwide(Bazilevich et al 1975 Reimers 1990 Savant et al 1997a)

The only place in the United States where Si fertilization isan established agronomic practice is in the Everglades Agricul-tural Area (EAA) in south Florida used mainly in the productionof sugarcane and rice Many agricultural-based research studiesinvolving Si started decades ago in this region Currently a largenumber of research projects on Si are happening in many partsof the United States because of the vast amount of research dem-onstrating the elementrsquos benefits to plant development and perfor-mance In addition the progress of Si research was recentlyhighlighted by the Association of American Plant Food ControlOfficials officially designating Si as a plant ldquobeneficial substancerdquofollowed by recognition of the official method (5-Day Na2CO3-NH4NO3ndashsoluble Si extraction method) for quantifying solu-ble Si in solid fertilizer products (Sebastian 2012 Sebastianet al 2013) Now Si may be sold as a fertilizer in the UnitedStates Recently the International Plant Nutrition Institute in-cluded Si in their fact sheet seriesmdashNutri-Facts furtherhighlighting the importance of Si in plant nutrition especiallyunder stressful conditions (httpwwwipninetnutrifacts-northamerican)

The documentation on the progress of Si research in agricul-ture has been assembled to view its value on a global perspectivehowever no work has been done so far to consolidate Si researchfindings for US agriculture This review contains information onthe dynamics of Si in plant and soil its uses and sources alongwith a comprehensive history and up-to-date documentation onpast and current Si research in US agriculture In addition the prin-cipal types of crops and soils of US lands perspectives on Si as aplant-beneficial nutrient in US crop production systems and thepotential of Si fertilization as a viable environment-friendly andprofitable agronomic practice are discussed in this review

Abundance Occurrence and Dynamics of Si in SoilThe pedosphere of the earthrsquos crust consists on average of

28 Si by weight ranging from 052 to 47 traces of Si are

wwwsoilscicom 1

FIG 1 Top 10 produced crops in the world in 2012 Seven of thesecrops are classified as Si accumulators (gt10 Si in dry matter)The values inside the bar are the reported shoot Si content byHodson et al (2005)

Tubana et al Soil Science bull Volume 181 Number 910 SeptemberOctober 2016

commonly present in carbonaceous rocks such as limestones andcarbonites whereas rocks such as basalt and orthoquartzite con-tain high concentrations of Si (23ndash47) (McKeague andCline 1963 Wedepohl 1995 Monger and Kelly 2002) Thechemicalweathering of silicate-containing minerals is the ultimatesource of dissolved Si (as monosilicic acid H4SiO4) which con-tributes to continental soil formation through linked biogeochem-ical reactions (Basile-Doelsch et al 2005) Silicon release to soilsolution from weathering of silicate-containing minerals is ratherslow and is governed by precipitation and neoformation ofauthigenic Si constituents Si adsorptiondesorption on varioussolid phases uptake and assimilation by vegetation and microor-ganisms preservation of stable Si forms in the profile and addi-tion from external atmospheric inputs (Cornelis et al 2011)These are linked processes and the largest interpool Si transfertakes place between biomass (biogenic silica from phytolithsand microorganisms) and soil solution (dissolved Si in the formof H4SiO4) at rates ranging from 17 to 56 1012 kg Si yminus1

(Conley 2002) In the ocean the largest interpool Si transfer

FIG 2 Different fractions of Si in soils Adapted fromTubana andHeckmaSo in order to publish this adaptation authorization must be obtained bothe owner of copyright in the translation or adaptation A color version

2 wwwsoilscicom

is between biogenic silica from diatoms and dissolved Si at67 1012 kg Si yminus1 (Treacuteguer et al 1995 Matichencov andBocharnikova 2001) Laruelle et al (2009) estimated that theamount Si transformed into biogenic silica averages 25 1012 kg yminus1

Silicon in soils is grouped into liquid adsorbed and solidphase fractions The composition of these fractions of Si com-pounds in the soil is presented in Fig 2 (Matichencov andBocharnikova 2001 Sauer et al 2006) The solid Si phase con-sists of poorly crystalline and microcrystalline amorphous andcrystalline forms of Si The largest solid phase fraction of Si oc-curs in crystalline forms mainly as primary and secondary sili-cates and silica materials Amorphous solid phase Si originatesfrom either as biogenic (originating from plant residues and re-mains of microorganisms) or lithopedogenic (Si complexes withAl Fe heavy metals and soil organic matter) materials(Matichencov and Bocharnikova 2001) The amount of amor-phous Si typically ranges from less than 1 to 30 mg gminus1 on a totalsoil basis (Jones 1969 Drees et al 1989) The solubility of Si inthe solid phase significantly affects the concentration of Si in theliquid phase Larger contribution is expected from amorphous sil-ica than quartz a crystalline silicate material The solubility ofamorphous Si ranges between 18 and 2 mM compared withquartzrsquos 010 to 025 mM Si (Drees et al 1989 Monger andKelly 2002) Biogenic silica also contributes to the concentrationof Si in soil solution and with solubility 17 times higher thanquartz this contribution to the dynamics of plant-available Si insoil solution is rather significant (Fraysse et al 2006) Both theliquid and adsorbed phase fractions of Si consist of H4SiO4 aswell as polysilicic acids and those dissolved Si complex with in-organic and organic compounds The silicic acid occurring as mo-nomeric (H4SiO4) is the plant-available form of soil SiPolymerization a process by which monomeric units of silicicacid form a chain results in the formation of polymeric silica orhigh-molecular-weight silica (Williams and Crerar 1985) UnlikeH4SiO4 polysilicic acid has not been shown to be plant-availablehowever it can link soil particles through the creation of silicabridges which improve soil aggregation andwater-holding capac-ity (Norton et al 1984) The liquid Si and adsorbed Si along with

n (2015) Adaptations are themselvesworks protectedby copyrightth from the owner of the copyright in the original work and fromof this figure is available in the online version of this article

copy 2016 Wolters Kluwer Health Inc All rights reserved

Soil Science bull Volume 181 Number 910 SeptemberOctober 2016 Silicon and Its Role in US Agriculture

amorphous forms of solid phase Si play an important role in thedynamics of plant-available forms of Si in the soil

Essentially the sufficiency or deficiency in soil Si is deter-mined by the rate of replenishment of Si in soil solution and therate of Si uptake during plant growth (Marschner 1995) Soil so-lution is an open system wherein leaching and diffusion affect dis-solution products produced during the weathering process ofsilicate minerals (Harley and Gilkes 2000) White (1995) evalu-ated published data on natural dissolution rates of several soilminerals during weathering process According to this summarythe weathering rate constant for silicate minerals (including pla-gioclase K-feldspar and hornblende) in natural environments(ie soil soil solution catchment and aquifer) ranged from 10minus205 to 10minus152 mol cmminus2 sminus1 Weathering rates can also beestimated in laboratory experiments however values are knownto be 1 to 3 orders of magnitude higher than natural systems(Paces 1983 Velvel 1986 Sverdrup 1990) Faimon (1998)provided an overview of the release of Si from feldspar (66SiO2) granodiorite (72 SiO2) and amphibolite (47 SiO2)based on long-term laboratory batch experiments In this workboth the rates of constant Si fluxes into soil solution from theseprimary rock minerals and Si fluxes out of solution intosecondary solids were estimated The amounts of Si releasedfrom feldspar granodiorite and amphibolite were 135 218and 557 mmol mminus2 dminus1 respectively whereas estimated fluxesof Si out of solution into secondary solids were 36 10minus374 10minus3 and 23 10minus2 μmol Lminus1 dminus1 respectively It isimportant to take note that in an open soil system the amount ofplant-available Si release to soil solution from weathering ofminerals is highly dependent on the composition of the soilsolution the reactions taking place at mineral surfaces fractionsof primary minerals and secondary phases along with theprocesses taking place in the rhizosphere (Colman andDethier 1986)

Source and UsesWollastonite a naturally occurring mineral rich in Si is

mined for production of ceramics friction products metallurgypaints and plastics (Virta 2004) It has an ideal compositionof 343 calcium (Ca) 243 Si and some minor amountsof aluminum (Al) iron (Fe) manganese (Mn) magnesium(Mg) potassium (K) sodium (Na) and minerals such as cal-cite diopside garnet idocrase and quartz (Virta 2004Maxim 2008) In 2004 the world production of wollastoniteore was estimated to be between 550000 and 600000 metrictons (Moore 2003) China is considered to be the leading pro-ducer with an estimated production of 300000 metric tonsDeposits of wollastonite have been found in the UnitedStates specifically in Arizona California Idaho NevadaNew Mexico New York and Utah (Virta 2004) It wasmined commercially in California and New York between1930 and 1970 The US production was rather limitedranging between 115000 and 127000 metric tons yminus1 in2003 (Hawley 2004)

Vasanthi et al (2012a) provided a review of Si occurrenceand its role in anthropogenic activity including usages in house-holds construction and architecture industrial applications andothers For example pure Si produced from the reduction ofSiO2 with carbon is the principal and cheap component of mostsemiconductor devices such as integrated circuits or computerchips Silicon is one of the principal materials in the photovoltaicand integrated circuits industries It is also used for manufacturingof Al-Si alloys to produce cast parts for the car industry Silicondioxide is mined for these industries as well as for construction


materials to produce glass concrete and cement In 1999 theUS sales of wollastonite were allocated mainly for production ofplastics (37) and ceramics (28) smaller fractions wereallocated for metallurgical applications (10) paint (10)friction products (9) and miscellaneous (6) (IndustrialMinerals 1999)

In agriculture Si-based compounds have many uses in cropproduction For example Si fluid is used as a spreading agentfor agrochemicals (Vasanthi et al 2012a) Silicon (R2SiOwhere R is an organic group) is safe to use and has goodwetting properties More importantly it spreads quickly andevenly thus is used as an agricultural adjuvant (spreadingagent) Silicate materials are useful carriers of bioproductsOrganic farming systems utilize nonndashsynthetic-based pesticidessuch as talc and phytosil to address the growing issues ofpesticide residues on food commodities and environmentalpollution (Vasanthi et al 2012b)

Uptake Assimilation and Si-Induced Mechanismsof Plant Resistance to Stress

Plants absorb Si as H4SiO4 At the pH levels of most agricul-tural soils H4SiO4 concentration in soil solution ranges from 01to 06 mM (Knight and Kinrade 2001) Absorption of H4SiO4

takes place at the lateral roots via active passive and rejectivemechanisms (Cornelis et al 2011) It is believed that in high Siaccumulators the amount of H4SiO4 taken up by active mecha-nism is greater than concentrations taken by mass flow becauseof the high density of Si transporters in roots and shoots facilitat-ing H4SiO4 movement across root cell membranes (Mitani andMa 2005) In rice both radial transport and xylem loading ofH4SiO4 are mediated by transporters Lsi1 and Lsi2 in roots andLsi6 in shoots (Mitani and Ma 2005 Ma et al 2006 2007)Takahashi et al (1990) categorized plants as high accumulator in-termediate accumulator or nonaccumulator relying on active pas-sive and rejective uptake mechanisms respectively Howeverwhen Takahashi and his colleagues developed this category itwas based solely on measuring Si in the foliage and did not rou-tinely measure this element in other plant organs Some plant spe-cies such as Chinese cabbage (Brassica rapa) crimson clover(Trifolum incarnatum) coffee (Coffea) green onions (Allium cepa)peppers (Capsicum) radishes (Raphanus sativus) and tomatoes(Solanum lycopersicum) are now known to concentrate more Siin their roots than in their shoots (Lewin and Reimann 1969Carre-Missio et al 2009 French-Monar et al 2010 Huanget al 2011)

So it may be assumed that all plants rooting in soil will con-tain Si in their plant tissue and that Si concentrations may exceedthose of many essential mineral elements For this reason it is un-likely that there are nonndashSi-accumulator plants Many researcherscontinue to note that plants classified as high accumulatorscontain 10 to 100 g kgminus1 Si in dry weight and most aremonocotyledons such as wheat sugarcane rice and barley(Hordeum vulgare) (Liang et al 2007 Ma et al 2001 Maand Takahashi 2002) IntermediatendashSi-accumulation plantscontain between 5 and 10 g kgminus1 dry weight and are mainlymonocotyledons whereas dicot plants with less than 5 g kgminus1

Si in dry matter are low Si accumulators The H4SiO4

absorbed by rootrsquos cells is deposited into leaf epidermal cellsAfter water removal the accumulated leaf H4SiO4 becomescondensed into a hard polymerized silica gel (SiO2nH2O) knownas phytoliths (Yoshida et al 1962 Jones and Handreck 19651967 Raven 1983) Silica deposited in leaf epidermal cells isimmobile and cannot be translocated to new growing leaves

wwwsoilscicom 3

TABLE 1 Proposed Si Mechanisms Associated With Plantsrsquo Improved Tolerance to Biotic and Abiotic Stresses

Mechanisms Specific Actions

External or involved insoil and root in preventingexcessive uptake of metal

High [H4SiO4] increases soil pHmdashprecipitates metal eg Al Cd Fe Mn (Lindsay 1979)H4SiO4 adsorbs Al hydroxides diminishing the activity of Al in solution (Baylis et al 1994)Mobile Al is strongly adsorbed on surfaces of silica (Schulthess and Tokunda 1996)Si induces oxidizing capacity of roots facilitating the conversion of plant-available Fe2+

to a less plant-preferred Fe3+ (Ma and Takahashi 2002)Si induces release of OHminus by roots which raises soil pH (Wallace 1993)

Reinforces plantrsquosprotective layerand mechanical structure

Silica in shoots enhances plantrsquos structural component and creates a hard outer layer (Belanger et al 2003)Improve overall mechanical strength and protective layer of plant(Epstein and Bloom 2005 Hayasaka et al 2008)

Mediatedprimedmechanisms of defense

Increased production of glucanses phytoalexins and PR-1 proteins (Rodrigues et al 2003 2004 2005)Enhanced deposition of phenolic-based compounds(Dann and Muir 2002 Belanger et al 2003 Rodrigues et al 2003)

Up- and down-regulation of a number of unique defensive and metabolic genes(Brunings et al 2009 Chain et al 2009 Fauteux et al 2005 Ghareeb et al 2011)

Interferes with the synthesis andor action of fungal ethylene (van Bochaven et al 2014)Sequestration of cations and enhancing activity of some protein molecules (Fauteux et al 2005)

Internal or in planta Enhances plants antioxidant systems (Gong et al 2005 Liang et al 2006 Inal et al 2009)Silica deposits in cell wall react (coprecipitate) to heavy metals impairing theirtranslocation inside the plants (Richmond and Sussman 2003 Ma et al 2004)

Prevents accumulation of Na of salt-stressed plants through Si-inducedreduction in transpiration (Yeo et al 1999)


The amount of literature documenting the benefits of Si onplants is vast and primarily highlights the value of Si fertilizationin maintaining plant productivity under stressed conditions(Epstein 1999 Li et al 2007) The established Si-inducedmechanisms to improve plantsrsquo resistance to biotic and abioticstresses take place in the soil the root system and inside theplant Table 1 summarizes some of the known currentmechanisms and actions involved externally and internally toinduce plantsrsquo resistance to a wide array of stresses Thecodeposition of silica and metals (eg Al Mn Cd) in solution(in soil and the root system) and in the plant results in reducedconcentrations of free toxic level of metal ions in plants Thesilica-precipitated metal ions are not easily translocatedreducing their potential toxic effects on the plant (Richmondand Sussman 2003 Ma et al 2004) Silicon deposition ofsilica in shoots and leaf epidermis also known as themechanical barrier hypothesis (Beacutelanger et al 2003 Epsteinand Bloom 2005 Rodrigues et al 2015) enhances theplantrsquos mechanical strength and protective layer This barrier isbelieved to help promote the plantrsquos resistance to pathogensreduce damage caused by insect feeding and grazing animalsimprove plantsrsquo tolerance to lack-of-moisture stress throughreduction in water loss via transpiration improve root resistance todry soils increase photosynthetic rates and reduce lodging rate(Savant et al 1997b Eneji et al 2005 Hattori et al 2005Cotterill et al 2007 Ma et al 2006 Datnoff et al 2009Rizwan et al 2012)

As mentioned previously the mechanical barrier formedfrom Si polymerization (silica opals or phytoliths) below thecuticle and in the cell walls was the first proposed hypothesisto explain how Si reduced or impeded fungal penetration(Wagner 1940 Heath and Stumpf 1986 Carver et al 1987)However new insights suggest Sirsquos effect on plant resistancemay also occur through mediated host plant resistance mecha-nisms against pathogen infection (Rodrigues et al 2015) Theyexplained that in such mechanisms an R gene of the plant formsproducts such as proteins or activates a defense mechanism

4 wwwsoilscicom

(s) that transfers resistance to specific plant pathogens Siliconhas been shown to up- and down-regulate certain genes and theirdefensive products in a number of host-pathogen interactions thatinclude rice (Magnaporthe oryzae) tomato (Ralstonia solanacearum)and wheat (Blumeria graminis f sp tritici) (Brunings et al 2009Chain et al 2009 Ghareeb et al 2011) Cheacuterif and his colleagues(1992a 1992b 1994) in Canada were the first to show that theactivities of pathogenesis-related proteins (peroxidase polyphenoloxidase and chitinase) were significantly stimulated by Si incucumber (Cucumis sativus) infected with Pythium speciesBeacutelanger et al (2003 2003) (Fawe et al 1998 2001) providedsome direct evidence showing that Si played more than a mechanicalrole Silicon stimulated phytoalexin production within the plantwhich was associated with cucumber resistance to Podosphaeraxanthii Based on these findings Si was hypothesized to beactively involved in triggering defense mechanisms in responseto fungal attack This hypothesis was further supported byDatnoff et al (1992) who reported that the fungitoxiccompounds identified as momilactones (rice phytoalexins) weredetected in Si-amended plants infected by the rice blastpathogen Magnaporthe oryzae (Rodrigues et al 2003 2004)They further demonstrated that a differential accumulation ofglucanase peroxidase and PR-1 transcripts was associated withlimited fungal colonization in the epidermal cells stronglyassociated with reduced rice blast development (Rodrigueset al 2005) Fauteux et al (2005) suggested that Si might act asa potentiator of plant defense responses or as an activator ofspecific signaling proteins that interact with several keycomponents of plant stress signaling systems ultimately leadingto induced resistance against pathogenic fungi Although themolecular mechanisms of how such priming is associated with Siare not well understood a growing body of research evidencesuggests that Si may be influencing plantrsquos endogenousdefensive hormone balances (Rodrigues et al 2015) Higherlevels of salicylic acid jasmonic acid and ethylene have beenreported to be induced by Si supplements in a number ofhost-pathogen interactions and confirmed by microarray analysis



(Rodrigues et al 2015) Genome-wide studies for tomato riceand wheat grown in soils amended with Si and inoculated byspecific plant pathogens have shown a differential and uniqueexpression of a large number of genes involved in host plantdefense mechanisms or metabolism compared with controlplants grown in nonndashSi-amended soil The association betweenSi and priming in plant-pathogen interactions was corroboratedby Vivancos et al (2015) but their findings also implied thatother mechanisms may also be involved besides the Si-dependentplant defense priming Clearly more research is warranted todetermine how Si potentiates host plant resistance against bothbiotic and abiotic stress

Silicon in Perspective History and DocumentedBenefits in US Crop Production Systems

In 1964 Clements published a chapter in the Annual Reviewof Plant Physiology entitled ldquoInteraction of Factors AffectingYieldrdquo He reported several instances where not only sugarcaneand other crops showed yield responses to application of silicatesOther articles were later published on Si (Bollard and Butler1966 Jones and Handreck 1967 Lewin and Reimann 1969Foy et al 1978) which focused on aspects of Si in relation tosoil-plant interactions Si uptake and transport and the mechanismby which Si enhances plant ability to withstand biotic (herbivoryand pathogen) and abiotic (metal toxicity) stresses Among thesepublications the review by Jones and Handreck (1967) provideda turning point in Si research They included a lengthy list ofreferences highlighting the value of Si from agricultural cropscience plant pathology and plant physiology perspectives Inlater work Carpita (1996) described Si in the structure andbiosynthesis of the cell walls of grasses

In the United States Maxwell (1989) produced the first anal-ysis that estimated plant-available Si in soils from the HawaiianIslands Research pursuing the role of Si as a nutrient for differentcrops began in the early 1900s (Conner 1921 Sommer 1926Lipman 1938 Raleigh 1939) In the study conducted byConner (1921) on soybean (Glycine max) Ca silicate slag applica-tion outperformed lime potash and phosphate treatments bycompletely precipitating toxic Al salts producing a 21 highergrain yield Growth of rice and millet (Pennisetum glaucum) wasimproved with Si addition (Sommer 1926) and seed heads ofmillet grown without Si were severely infected by plant patho-genic fungi Lipman (1938) made similar observations regardingthe effects of Si on growth and found seed production was en-hanced in sunflower (Helianthus annuus) and barley Raleigh(1939) documented a 44 increase in beet (Beta vulgaris) pro-duction in acid soils with high Al salts with the addition ofCa silicate slag compared with Ca hydroxide as a liming agentHe also observed that roots became necrotic and were coveredby an organismal growth fungal or fungal-like mass whensugar beet was grown in a nutrient solution without Si Therole of Si was evaluated on solution-cultured tomato (Woolley1957) and barley (Williams and Vlamis 1957 1967) furtherconfirming the potential benefits of Si in plants

The first direct use of Si as a fertilizer rather than as a limingagent was tested for sugarcane production in Hawaii (Clements1965a) The initiation of this study was instigated by the increas-ing incidence of leaf freckling (small rust-colored or brownishspots on the leaf surfaces) in cane plants These cane plants weresuspected to be suffering from a Si deficiency A series of field ex-periments demonstrated that the application of Ca silicate slag notonly reduced or completely eliminated leaf freckling but also re-sulted in significant increases in cane tonnage and stalk sucrosecontent (Clements 1965b) These positive returns fromCa silicate


slag application were also accompanied by a drastic reduction inthe ratio of Mn and silica content in cane leaves Later studies alsoshowed Si precipitated Al and Mn which alleviated injuries toroots and tops of sugarcane grown on soils with low pH and toxicconcentrations of metals (Clements et al 1974) On similar soilsAyres (1966) showed increases of 9 to 18 in cane yield and11 to 22 in sucrose content following the application of62 Mg haminus1 electric furnace slag While Ayres (1966) agreed thathighly soluble Si depressed Al and Mn uptake by sugarcane theamount of soluble Si in the soil was inherently low expressingthe view that there was a certain concentration of plant-availableSi below which it would not be sufficient for normal growth ofsugarcane regardless of the supply of other available nutrientsSilicon was later recognized as ldquoagronomically essentialrdquo for sug-arcane production (Chen and Lewin 1969 Fox and Silva 1978Lux et al 1999 Pilon-Smits et al 2009)

Similar Si benefits in sugarcane production as those reportedin Hawaii in the 1960s were documented in the EAA of southFlorida as earlier reported in Hawaii in the 1960s (Elawad et al1982) The majority of soils in this region are classified as organicsoils or Histosols These soils have a relatively small mineral frac-tion approximately 20 with correspondingly low bulk densitySnyder et al (1986) noted that fields in this region when farmed toirrigated rice showed Si deficiency and that the application of1 Mg haminus1 Ca silicate slag increased rice grain yields by greaterthan 30while reducing the incidence of grain discoloration Be-cause of the low plant-available Si content of Histosols the bene-fits of Si fertilization to sugarcane rice and citrus production arecommonly observed in this region (Elawad and Green 1979Elawad et al 1982 Deren et al 1994 Matichenkov et al1999) Sugar yields depending on crop age increased by 25to 129 in response to application of Ca silicate slag (Andersonet al 1987 Elawad et al 1982) For both sugarcane and ricecrops Si fertilization has become an established practice on com-mercial production fields in this region

Several field and greenhouse studies in Florida demonstratedthat Si will influence many components of host resistance includ-ing incubation period latent period lesion number and lesionsize Si also augments susceptible and partial resistance almostat the same level as complete genetic resistance and suppressesplant disease as effectively as do fungicides (Datnoff et al1992 Datnoff and Snyder 1994 Datnoff et al 1997 Rodrigueset al 2001 Seebold et al 2001 Brecht et al 2004) A 1-year re-sidual Si application was also effective in reducing blast andbrown spot development in rice while enhancing yields more ef-fectively than fungicides alone (Datnoff et al 1991 Datnoffet al 1997) Consequently growers may save initial or additionalapplication costs for either fungicides or Si fertilizer while provid-ing positive environmental benefits (Alvarez and Datnoff 2001)

Silicon research in the areas of plant physiology soil fertilityand agronomy began to expand in other regions of the UnitedStates In Louisiana a series of field trials were established in2000 to evaluate the impact of silicate slag application to sugarcane(Viator et al 2004) Sugar yield increased by a total of 3700 kghaminus1 (P lt 005) for the whole crop cycle (three harvestings) of canevariety LCP 85-384 with a one-time application of 45 Mg haminus1

Ca silicate slag at planting (Viator et al 2004) Tubana et al(2012) showed that this Ca silicate application rate increased sugaryield by 1450 kg haminus1 (P lt 001) The potential of Si fertilizationin disease management was also evaluated in rice production sys-tems in Louisiana (Bollich et al 2001) In Kansas the depositionpattern of Si in tissues of a mature corn (Zea mays L) was studiedby Lanning et al (1980) In Delaware the potential of Si to reduceAs uptake by rice was documented by Seyfferth and Fendorf(2012) They attributed the reduction in grain and strawAs uptake

wwwsoilscicom 5


to competition between H4SiO4 andH3AsO3 (form of As taken upby plant) for adsorption sites on soil colloids and subsequent plantuptake The effect of Si on growth and drought stress tolerance ofcorn rice soybean and wheat was the central focus of a series ofstudies conducted by Janislampi (2012) in Utah Under droughtand salt stress conditions both corn and wheat biomass at vegeta-tive stage increased by 18 and 17 respectively (P lt 005) be-cause of Si fertilization Silicon also improved water useefficiency of corn by as much as 36 (P lt 005)

In New Jersey research plots to study Si nutrition were firstestablished in 2000 at the Rutgers Snyder Research and ExtensionFarm in Pittstown (Heckman 2012) Responses of cropsplantssuch as pumpkin (Cucurbita maxima) cabbage (Brassicaoleracea) winter wheat corn oats (Avena sativa) and grassesto Ca silicate slag applications were documented After more thana decade of research enough data to justify Ca silicate slag as aneffective liming material and Si fertilizer were collected Increasesin yields observed in these crops had corresponding increases inSi uptake and reduced insect damage (eg European corn borer)and disease development (eg powderymildew) One of the high-lights of these studies was the residual benefit of Ca silicate slagextending up to 3 to 4 years after the last application economi-cally justifying the value of this agronomic practice not only infield crops but also in forages and horticultural crops The valueof Si fertilization was also pursued in horticulture and floricultureinvolving scientists from Illinois Maine Oklahoma and Ohio(Kamenidou 2002 Frantz et al 2008 Kamenidou et al 2009Hogendorp et al 2012)

Several studies also evaluated the value of integrating Si fer-tilization in rice insect management in Louisiana (Sidhu et al2013) and horticultural crops in Kansas (Cloyd 2009) and

TABLE 2 Estimated Shoot Si Uptake Based on 10-Year Average (200in the United States and Their Reported BiomassHarvested Portion

Crops

HarvestArea Production BH

RatioDagger AuthorsMillion Ha Million Tons

Barley 1278 462 15 Brown 2003Maize 32555 30781 10 Renard et al 1997Oats 0556 126 14 Brown 2003Rice 1203 948 10 Summer et al 2003Sorghum 2307 933 10 Renard et al 1997Soybeans 29841 8469 15 Renard et al 1997Sugar beet 0485 2918 10 Dadkhah and

Grifiths 2006Shaw et al 2002

Sugarcane 0362 2742 014 Hassuani et al 2005Wheat 19865 5835 15 Renard et al 1997Total 88452

Harvested portion of the crops (eg stalk in cane grain in rice roots for bDaggerBiomass ratio to harvested parts of the plant harvested = grain stalks rooparaCitations for the BH ratiopoundEstimated biomass (eg straw in rice stover in corn leaves in sugarcane)sectComputed as the product of production level BH ratio and shoot SiβSi content in shoot reported by Hodson et al (2005)ccedilComputed as estimated shoot Si uptake divided by the 10-year average haraLatshaw (1924) (stovermdashleaves stems and cobs)daggerDraycott (2006)bAverage shoot Si uptake estimated as total annual shoot Si uptake divided

6 wwwsoilscicom

Illinois (Hogendorp et al 2012) The augmentation of soil usingSi-containing fertilizer resulted in increased rice Si uptake by asmuch as 32 leading to a significant reduction in both relativegrowth rate and the boring success of Diatraea saccharalis larvaeon Si-treated rice plants (Sidhu et al 2013) Conversely green-house studies by Cloyd (2009) and Hogendorp et al (2012) dem-onstrated that the application of Si-based fertilizers did not raise Siuptake of fiddle-leaf fig (Ficus lyrata) nor did Si inhibit insectpest feeding and outbreaks They attributed the lack of responseto the inherent inability of horticultural crops such as fiddle-leaffig plant to accumulate Si However Frantz et al (2008) noted thatthere are several new floriculture species (Zinnia elegans Impa-tiens hawkeri verbena and calibrachoa) which take up and accu-mulate significant concentrations of Si this challenges the earlierphylogenetic studies suggesting that Si uptake is limited to only afew plant species Similar studies in Oklahoma (Kamenidou2002 Kamenidou et al 2009) revealed that the application ofSi improved several horticultural traits of selected cut flowers

Crop Removal Rates and Soil Si StatusCrop production removes large quantities of Si from soil On

a global perspective the estimated amount of Si removed annuallyby different agricultural crops is between 210 and 224million tons(Bazilevich et al 1975 Reimers 1990 Savant et al 1997a)Larger removal rates are estimated from highndashSi-accumulatorcrops such as wheat sugarcane and rice Sugarcane removesapproximately 300 kg haminus1 yminus1 whereas rice is as much as 500 kgSi haminus1 yminus1 (Meyer and Keeping 2001 Blecker et al 2006Makabe et al 2009) These amounts are much higher than the re-moval rates of primary essential nutrients such as nitrogen (N)

4ndash2013) of Harvested Area Production Level of Principal CropsRatio and Shoot Si Content

ShootBiomasspound

ShootSiβ

Estimated Annual Shoot SiUptakesect

Shoot SiUptakeccedil

Million tons g kgminus1 Tons kg haminus1

693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts

production computed as the product of production and BH ratio

vested area

by the total harvest area



phosphorus (P) and K After years of continuous cropping har-vesting of crops for human consumption can eventually resultin reduction of plant-available Si in soils (Meunier 2003Meunier et al 2008) To put this in perspective for rice productionentirely relying on release of H4SiO4 from amorphous silica as its Sisource the supply of plant-available Si is expected to be exhaustedafter 5 years of continuous cultivation (Desplanques et al 2006) Areview by Savant et al (1997b) suggested that the decline in yieldsof rice grown in many areas of the world was associated with soildepletion of plant-available Si This may pose further problems insoils with large fractions of quartz sand high organic matter con-tent and characterized as highly weathered leached acidic andlow in base saturation (Foy 1992 Datnoff et al 1997)

The US produces a diverse group of crops that are used forfiber grains and hay legumes oilseeds root crops sugar cropsand vegetables In 2014 the total production of corn reached361 million tons harvested from more than 336 million hectaresof land this production level represented approximately 35 ofworld production (USDA-NASS 2015) Based on the averageharvested area and production level of principal US crops in thelast 10 years corn and soybean have been the nationrsquos most im-portant crops (Table 2) According to Takahashi et al (1990)highndashSi-accumulator plants have 10 to 100 g kgminus1 Si content inshoots Therefore with the exception of corn the principal cropsgrown in the United States are high Si accumulators While cornis not classified as a Si accumulator by this standard its high pro-duction level translates into a large amount of Si removal throughplant uptake To present an overview of Si uptake by these cropsseveral published data were consolidated to estimate shoot Si up-take which is defined as the total amount of Si contained in theentire crop at maturity (eg in the straw grain roots and huskof rice) However there is limited information on Si content ofthe harvested portion of crops (eg grains for cereal stalks forsugarcane roots for sugar beets) While there are some knownvalues they are not yet published (Tubana unpublished data)For example the averaged Si content for corn grain is 26 g kgminus1

(n = 64 samples) whereas rice panicles (grain + husk) containan average of 23 g kgminus1 (n = 256) and shredded unpressed cane

TABLE 3 Estimated Annual Si Removed from Soil per Area Basis byHarvested Area and Published Si Removal Rate by Crop per Hectare

Crop

Harvest Area Silicon Removal Rate

Million ha Range kg haminus1 Medianb kg haminus1

Barley 1278 50ndash200 125Maize 32555 50ndash200 125Oats 0556 50ndash200 125Rice 1203 500 500Sorghum 2307 50ndash200 125Soybeans 29841 50ndash200 125Sugar beet 0485 50ndash200 125Sugarcane 0362 300 300Wheat 19865 50ndash150 100TotalCroplanda 168810 50ndash200 125

aUS total land in 2007 planted to food crops (eg wheat rice sweet potatoesflaxseed) (USDA-NASS 2007)

bFor Si content in range values determined by adding the maximum and mdaggerCitation for the Si removal rateDaggerComputed as the product of 10-year average harvest area and average Si re


stalks average 49 g kgminus1 Si (n = 192) The Si contained in the har-vested portions of these crops is lower than the shoot Si contentreported by Hodson et al (2005) and Draycott (2006) (Table 2)The published average biomass to harvested portion (BH) ratioof these crops was then utilized to estimate the biomass or residueof the given production level in the past 10 years The annual es-timated shoot Si uptake annually by these principal crops wascomputed by multiplying shoot biomass estimate by the shoot Silevel and then further dividing this value by the average10-year harvested area to obtain shoot Si uptake per hectareby these crops

Shoot SiBiomass uptake kg ha‐1 frac14 Average annual productionHarvested portion x B=H ratio x shoot Si content

10‐year Average harvested area

The high US corn production level in the last 10 years pro-duced the highest annual shoot Si uptake at 421 million tons evenwith an intermediate Si content of 136 g kgminus1 (Table 2) Wheatfollowed with 214 million tons followed by soybean a dicotplant species estimated at 177 million tons The actual removalrate by plant uptake is certainly higher than these estimates asthe harvested parts of these crops were not accounted Even sothe estimated shoot Si uptake per hectare of these crops almostconsistently exceeded uptake of primary nutrients such as N Pand K Most notable are rice sugar beet sugarcane and wheatwith an estimated shoot Si removal of 329 1408 160 and108 kg Si haminus1 respectively The extremely high shoot Si uptakeestimate for sugar beet can be attributed to the high Si content re-ported by Draycott (2006) at 234 g Si kgminus1 In fact the sugar beetdry matter (tops) contained approximately 115 g Si kgminus1 whichcould explain the observed reduction in digestibility and metabo-lizable energy content of tops Including all field crops on this listthe total estimated annual shoot Si uptake is 955 million tons andthe average shoot Si uptake is 107 kg haminus1 On the other handthere were reports of the Si removal rate of rice sugarcane andwheat being at 500 300 and 50 to 150 kg haminus1 respectively(Meyer and Keeping 2001 Makabe et al 2009 Bazilevich1993) Bazilevich (1993) also reported plant average Si uptakeranging from 50 to 200 kg haminus1 Using the 10-year average

Principal Crops in the United States Based on 10-Year Average

Authordagger

Estimated Si Annual Removal RateDagger

tons

Bazilevich 1993 159766Bazilevich 1993 4069371Bazilevich 1993 69475Makabe et al 2009 601287Bazilevich 1993 288347Bazilevich 1993 3730068Bazilevich 1993 60604Meyer and Keeping 2001 108569Bazilevich 1993 1986480

11073967Bazilevich 1993 21101250

beans) feed crops (eg corn-all barley hay) and other crops (eg cotton

inimum values then divide by 2

moval rate for each crop

wwwsoilscicom 7


harvested area and these removal rate estimates US production ofrice sugarcane wheat and the rest of these principal crops can re-move a total of 1107 million tons Si from the soil every year(Table 3) If this plant-Si average is used to estimate Si removalfrom the 16881 million hectares of cropland (USDA-NASS2007) this translates to approximately 211 million tons of Si re-moved annually The estimated area planted to these 10 principalcrops is approximately 50 of the total US cropland

The Si in shoots can be returned to the soil (recycling)through plant residue incorporation There are conflicting reportson the turnover rates of plant-available Si from decomposition ofplant materials Ma and Takahashi (2002) noted that the positiveeffect of rice straw incorporation on plant-available soil Si is longterm in nature and is not fully realized immediately after straw in-corporation However Marxen et al (2016) reported thatphytoliths from fresh rice straw are soluble at a rate of 2 to25 per day during the first 33 days of their experiment thiswas followed by decreasing Si release rates suggesting that phy-tolith solubility decreases over time in soil The findings ofFraysee et al (2009) were similar wherein phytoliths extractedfrom horsetail had a dissolution rate of approximately 06 and3 phytolith-Si dminus1 at pH 6 and 86 respectively Most Si in thesoil is in an inert form and only a small fraction is soluble andavailable for plant uptake whereas most Si in mineral soils is heldin the crystalline structure of sand silt and clay particles a Siform unavailable for plant uptake Soils vary significantly in theirability to supply plant-available Si In general soils in which Sifertilization will likely result in increases in crop yields are typi-cally highly weathered leached tropical soils with low pH basesaturation and silica-sesquioxide ratios (Silva 1973) These soilsare classified as Ultisols and Oxisols Their clay minerals are pre-dominantly hydrated Al and Fe oxides and kaolite characterized

FIG 3 Distribution of Ultisols and Histosols in US land area Adapted froprotected by copyright So in order to publish this adaptation authorizatoriginal work and from the owner of copyright in the translation or adaptthis article

8 wwwsoilscicom

as high P-fixing soils Soils that are less weathered or geologi-cally young have the capacity to supply higher amounts ofplant-available Si than highly weathered soils

Soils known to have limiting plant-available Si content foundin the United States generally belong to the following soils ordersHistosols Ultisols Spodosols Inceptisols and Entisols Ultisolsare common in the Eastern United States occupying approximately92 of the total US land area (Fig 3) These are acidic soils char-acterized by having a low amount of plant-available Ca Mg andK These soils have undergone intenseweathering and leaching asis commonly found in warm humid regions of the United Stateswith high average annual rainfall and are not suited for continuouscrop production unless treated with fertilizer and lime Accumu-lated clay and the presence of Fe oxides are common in the sub-surface horizon of these soils Plant-available Si in Ultisols isgenerally low in contrast to the Mollisols that are common inthe US Great Plains Histosols of the EAA of south Florida arecomposed mainly of organic materials (20ndash30 by weight)and are known to have low quantities of plant-available Si Pro-duction areas in this region are known to respond significantlyto Si fertilization Histosols occupy approximately 16 of theUnited Statesrsquo land area (Fig 3) Spodosols are acid soils character-ized by a subsurface accumulation of Al- and Fe-humus complexSimilar to Ultisols these soils require liming in order to be ag-riculturally productive These soils are typically formed fromcoarse-textured parent material and occupy approximately 35of the US land area (Fig 4) Many regions in the United Stateshave soils belonging to the weakly developed Entisols andInceptisols that are believed to have low levels of plant-availableSi as well (Fig 5) Entisols generally have little or no evidenceof pedogenic horizons development many are sandy or veryshallow (Soil Survey Staff 1999) This is the most extensive soil

m Soil Survey Staff (1999b) Adaptations are themselves worksionmust be obtained both from the owner of the copyright in theation A color version of this figure is available in the online version of


FIG 4 Distribution of Spodosols in US land area Adapted from the National Resources Conservation Service 2014 Adaptations arethemselves works protectedby copyright So in order to publish this adaptation authorizationmust be obtained both from the owner of thecopyright in the original work and from the owner of copyright in the translation or adaptation A color version of this figure is available in theonline version of this article


order occupying approximately 123 of the US land area Soilsbelonging to Inceptisols are commonly found in humid andsubhumid regions widely distributed in the US land area (approx-imately 97) often found on fairly steep slopes young geomor-phic surfaces and on resistant parent materials Horizons of thesesoils are altered and known to have many diagnostic horizonsSoil texture and the duration of cropping systems are criteria otherthan soil order which can provide an overview of plant-availableSi status Soils with large fractions of quartz sand that have beenfarmed for many decades are likely to have low quantities ofplant-available Si (Datnoff et al 1997)

Silicon Fertilization GuidelinesmdashWhere DoWe Stand

Soil Extraction Procedure and Critical LevelsThe most common method to quantify the concentration

of Si in water soil extracts and plant digest samples is viathe molybdenum blue colorimetry (Hallmark et al 1982)Monosilicic is the only form of silicic acid that is molybdate re-active forming an intense blue color in solution which in-creases with H4SiO4 concentration The presence of otherforms of Si (eg polysilicic acid) does not affect the formationof Si-molybdate blue complex Silicon in solution can be mea-sured by inductively coupled plasma-optical emission spectrome-try which can also measure all other forms of Si in solutionincluding those that are not plant available Thus this limitationshould be considered when estimating plant-available soil SiConversely for quantifying total Si content in plant samples in-ductively coupled plasma-optical emission spectrometry analysismay not pose any complications (Frantz et al 2008)

From the vast amount of literature in the last 50 years manyprocedures have been established and standardized for extractingdifferent Si forms not only plant-available forms but also Si fromamorphous silica and allophane in soils and sediments (Sauer


et al 2006) However the abundance of Si in soil is interpreteddifferently when it comes to fertilization guidelines where themost important fraction of Si is the form available for plant uptakePlant-available Si is composed of H4SiO4 both in liquid (soil solu-tion) and adsorbed phase (to soil particles) Tubana and Heckman(2015) summarized solutions which have been used to extractand estimate plant-available Si including water calcium chloride(CaCl2) acetate acetic acid sulfuric acid (H2SO4) and citric acid(Table 4) The extraction procedures associated with these solutionshave undergone a series of modifications which generally re-sulted in shorter extraction time requirements The choice ofsolution is critical because the amount of plant-available Si es-timated by these extraction procedures differs and so would bethe interpretation of results and fertilizer recommendation Forexample Fox et al (1967) used H2SO4 acetic acid water andCa(H2PO4)2 to extract Si from soils of Hawaii Water consis-tently extracted the least amount of Si whereas those soilsdominated by montomorillonite kaolinite goethite andgibbsite contained the highest amount of Si based on the Ca(H2PO4)2 procedure The H2SO4 procedure extracted thehighest Si content from soils which contained large fractionsof allophane whereas the Si content of soils determined bythe acetic acid procedure fell between water and Ca(H2PO4)2H2SO4 Recent works by Tubana et al (2012) and Babuet al (2013) have also demonstrated that the amounts of Si deter-mined using different extractors for Midwest and southern USsoils varied significantly According to Babu et al (2013) theamount of extractable Si was in the order of citric acid gt aceticacid (24-h rest + 2-h shaking gt 1-h shaking) gt Na acetate gt ammo-nium acetate gt CaCl2 gt water for soils representing some 130mineral soils of Louisiana currently farmed to different fieldcrops The soil Si determined by 05M acetic acid solution rangedfrom 3 to 300 mg kgminus1 Similar study was done by Wang et al(2004) except that they included Mehlich-3 solution The amountof extracted Si was in the order of Mehlich-3 gt citric acid gt 01 M

wwwsoilscicom 9

FIG 5 Distribution of weakly-developed Inceptisols and Entisols in US land area Adapted from the National Resources Conservation Service2014 Adaptations are themselves works protected by copyright So in order to publish this adaptation authorization must be obtainedboth from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation A color version ofthis figure is available in the online version of this article


HCl gt acetic acid gt acetate buffer gt ammonium acetate gt watersuggesting that Mehlich-3 solution likely extracts solutionexchangeable and adsorbed Si fractions

Establishment of soil Si test interpretation and fertilizationguidelines require knowledge of the critical Si concentrations inthe soil defined as the point on an economic crop response curvecorresponding to plant-available soil Si concentrations at whichmaximum crop yield is attainable Beyond this critical Si concen-tration it is expected that crop response to Si fertilization will notresult in further significant yield increases whereas below this

10 wwwsoilscicom

concentration there is the likelihood of a crop significantlyresponding to Si fertilization It is expected that critical Si concen-trations just like any other plant-essential nutrients will vary withsoil type crop species and soil testing procedure The critical Silevel established for the organic and mineral soils in southFlorida (characterized by having low clay Al and Fe contents)was based on 05 M acetic acid procedure (1-h shaking) Usingsugarcane as a test crop the critical Si level was determined tobe 32 g mminus3 (McCray et al 2011) and 19 mg Si kgminus1 for a ricecrop (Korndorfer et al 2001) Elsewhere in the world depending


TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble

SchachtschabelandHeinemann1967

10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin

60mLincubateat40degC

for2wk

Water

soluble

NonakaandTakahashi19881990

10gin

100mL1

-hshaking

Water

soluble

Korndoumlrferetal1999

CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087

Maceticacidadjustedto

pH4

10-g

samplein

100mLsolutio

n5-hoccasionalshakingat40degC

Solublesomeexchangeable

Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate

5(05M)NH4acetateadjusted

topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking

Solubleexchangeableadsorbed

Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC

Solubleexchangeableadsorbedto

sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking


SauerandBurghardt20002006

H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin

10mLMehlich-3solutio

n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo

inordertopublishthisadaptatio

nauthorizationmustbeobtained

bothfrom

theow

nerofthe

copyright

intheoriginalworkandfrom

theow

nerof

copyrightinthetranslationor

adaptation


copy 2016 Wolters Kluwer Health Inc All rights reserved wwwsoilscicom 11


on soil type and extraction procedure the critical Si concentrationvaried significantly For example the critical level ranged be-tween 71 and 181 mg kgminus1 for wheat grown on calcareous soilsusing Na acetatendashacetic acid as the extracting solution (Lianget al 1994 Xu et al 2001) Narayanaswamy and Prakash(2009) showed large differences in critical Si concentrationsfor rice grown on acidic soils in India because of extractingsolutions 54 versus 207 mg Si kgminus1for 05 M acetic acid (1-hshaking) versus 0005 M H2SO4 respectively For select mineralsoils from the Midwest and southern United States Tubana et al(2012) suggested that critical Si concentrations ranged between120 and 150 mg Si kgminus1 when using ryegrass biomass as the plantresponse variable

Plant TissuemdashTesting Procedure and Critical LevelStandardization of procedures in plant tissue Si testing has

not encountered as many challenges as the standardization of soilSi testing Only a few procedures are established for determiningtotal Si content in plant tissue gravimetric method hydrofluoricacid solubilization autoclave-induced digestion with strongNaOH solution or microwave digestion assisted with nitricacidndashhydrofluoric acid (Yoshida et al 1976 Novozamsky et al1984 Elliot and Snyder 1991 Feng et al 1999) Themost widelyused method was the autoclave-induced digestion method devel-oped by Elliot and Snyder (1991) because it is relatively rapidand does not require costly specialized instrumentation Howeverthere were many reports regarding low precision of themethod and at times underestimation of Si value in the plant(Taber et al 2002 Haysom and Ostatek-Boczynski 2006)Excessive foaming caused some undigested samples to adhereto the walls of plastic tubes and during autoclaving the sampleparticles had lower or no contact at all with the NaOH andH2O2 which resulted in incomplete digestion This was lateraddressed by Kraska and Breitenbeck (2010a) with the additionof octyl-alcohol which eliminates the excessive foaming causedby H2O2 addition The stability of color development was pro-longed as well with the addition of 1 mL of 5 mM ammoniumfluoride and the method was simplified by using a bench-top oven(95degC) over an autoclave After these modifications the procedureis now called the oven-induced digestion procedure (Kraska andBreitenbeck 2010a) Recently nondestructive accurate andhigh-throughput methods in assessing Si in plants were evaluatedReidinger et al (2012) assessed Si in plants using a portable x-rayfluorescence spectrometer with a detection limit of 0014 SiSmis et al (2014) calibrated plant Si extracted by wet alkaline(01 M Na2CO3) solution according to Meunier et al (2013) withthe values near-infrared reflectance spectroscopy technique

Silicon content of plant tissue is an accepted parameter forevaluating plant-Si status Currently there are few published planttissue critical Si concentrations not only in the United States butalso elsewhere in the world The published concentrations aremainly for rice and sugarcane The critical Si level establishedby Snyder et al (1986) for rice grown on organic soils of theEAA of south Florida using straw was 30 Recent work byKorndoumlrfer et al (2001) established critical concentrations for rice(between 17 and 37) using similar straw sampling materialUsing the most recent fully expanded leaf in rice (Y-leaf) atmid-tillering Kraska and Breitenbeck (2010b) noted 50 as aconcentration used to indicate sufficient Si for rice in LouisianaUsing sugarcane top visible dewlap leaf as sampling materialAnderson and Bowen (1990) identified the critical Si contentwas 10 whereas McCray and Mylavarapu (2010) set a lowervalue of 05 To maximize sugarcane yield the Si content in leaftissue should be more than the reported critical Si concentration

12 wwwsoilscicom

(Snyder et al 1986) It is important to note that the critical Si con-centrations are very specific to crop species location and sam-pling material underscoring the need to establish site-specificplant-Si content interpretations

Sources of Silicon FertilizerThe reduction of H4SiO4 in soil solution triggers several pro-

cesses in the soil system as a means to replenish the lost Si untilequilibrium is reached between the liquid and solid Si phasesThere are soils capable of immediately replenishing lost Si in soilsolution (eg crop removal) but certain types of soil may takesome time to replace lost Si even under accelerated mineralweathering depolymerization and dissolutions of silicatecomplexes with heavy metals hydroxides and organic matterConsequently fertilization using different sources rich in Si be-comes a logical approach

The first patent for using Si-rich slag as fertilizer was ob-tained in the United States in 1881 (Zippicotte 1881) While thenaturally occurring wollastonite Ca silicate is more soluble andcontains high amounts of Si the refining process of this mineral islabor-intensive and expensive which limits its mass production asa fertilizer (Park 2001 Maxim et al 2008) Using this processhigh application rates alone can make this Si fertilizer extremelyexpensive on top of its transportation cost to the field andmachin-ery costs for application In the United States the expenses allot-ted to transportation and machinery may be affordable because ofrelatively good infrastructure and crop subsidies but these expensescould be more problematic elsewhere in the world particularly indeveloping countries Nowadays byproducts of industrial proce-dures such as the smelting of wollastonite Fe andMg ore and elec-tric production of P are commonly used as Si fertilizers (Elawad andGreen 1976 Snyder et al 1986) These are relatively inexpensivesources of Si for crop production Compared with wollastonite sil-icate slags contain smaller fractions of easily soluble Si but theyhave added benefits such as liming agents typically with similarCa carbonate equivalent and as sources of some plant-essential nu-trients (Heckman et al 2003 Gascho 2001 White et al 2014) Inaddition some slags unlike wollastonite can provide a balancedsupply of Ca and Mg

The amount of plant-available Si and composition of silicateslags differ because of differences in speeds of cooling and gran-ular size of the material (Takahashi 1981 Datnoff et al 1992Datnoff et al 2001) While silicate slags are more economicalto use as Si fertilizer versus wollastonite as Si fertilizer producersshould not overlook the amount of plant-available Si present in thesilicate slag Several methods for quantifying plant-available Sifrom industrial byproducts have been tested and thus far identifiedthat the Na2CO3 + NH4NO3 extraction methods have been identi-fied as suitable for solid Si sources whereas the HCl + HF diges-tion was suitable for liquid sources (Buck et al 2011) Recentlythe 5-day Na2CO3-NH4NO3 soluble Si extraction method was de-veloped for solid fertilizer products (Sebastian 2012 Sebastianet al 2013) Total Si and soluble Si of some industrial byproductsources are reported in Table 5 Included in the list are organicsources biochar rice hull ash and livestock manure compostsStraw from wheat and other small grain crops contains highamounts of Si wheat straw Si concentrations range from 15 to12 g kgminus1 (Heckman 2012) In addition to this fresh rice strawcan be a potential source of Si The potential of fresh straw assource of Si is encouraging based on recent findings by Marxenet al (2016) indicating that this plant material contains largeamount of highly soluble phytoliths This in turn can replenishthe amount of plant-available Si taken up by plant from thesoil solution


TABLE 5 Total and Soluble Si Content of Different Sources of Silicon Fertilizer

Source

Silicon Content

Chemical Composition ReferencesTotal Si g kgminus1 Soluble Si g kgminus1

Wollastonite 242 36 Calcium silicate Sebastian et al 2013242 65 Calcium silicate Haynes et al 2013

MgSiO3 (talc) 285 10 Magnesium silicate Sebastian et al 2013Silica gel 467 58 Not known Sebastian et al 2013Silica blend (monocal or withFeSO4 NH4NO3 KCl)

121 18 Calcium silicate (mainly) Sebastian et al 2013

CaSiO3MgSiO3 blend 120 22 Calciummagnesium silicate Sebastian et al 2013LiquidsolutionK2SiO3 liquid 97 76 Potassium silicate Sebastian et al 2013NaSiO3 liquid 56 mdash Sodium silicate Abed-Ashtiani et al 2012Silicic acid 360 64 mdash Sebastian et al 2013

Industrial by-productIronsteel slag 54 46 Calcium silicate Haynes et al 2013Electric furnace slag 211 148Dagger Calciummagnesium silicate Gascho and Korndorfer 1998

203 50 Sebastian et al 2013Blast furnace slag 173 17 Calciummagnesium silicate Haynes et al 2013Processing mud 68 04 mdash Haynes et al 2013Fly ash 291 03 mdash Haynes et al 2013

230 01 Raghupathy 1993Plantorganic materialMiscanthus biochar 383 mdash Silica Houben et al 2014Rice hull fresh 70ndash92 mdash Silica Sun and Gong 2001Rice hull ash gt280 mdash Silica Kalapathy et al 2002Cattle manure compost 95 mdash mdash Kobayashi et al 2008Swine manure compost 34 mdash mdash Kobayashi et al 2008Poultry manure compost 17 mdash mdash Kobayashi et al 2008

Dagger2 Citric acid procedure

Five-day Na2CO3-NH4NO3 soluble Si extraction method

Adapted from Tubana and Heckman (2015) Adaptations are themselves works protected by copyright So in order to publish this adaptation authori-zation must be obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation


The use of Si-containing solution applied as foliar spray hasan advantage in terms of ease of application at manageable ratesand not altering soil pH brought about by high application ratesof solid Si sources with high liming potential (Tubana et al2012 Haynes et al 2013) While there is a growing interest onthe use of foliar Si solution limited studies have been conductedin the United States (Kamenidou 2002 Kamenidou et al 2009Lemes et al 2011 Tubana et al 2013 Agosthinho et al2014) In addition even if there was a positive plant response tofoliar Si the foliar absorption of Si remains questionable becauseno transport mechanisms have been found to occur in this plant or-gan to date (Rodrigues et al 2015)

Analytical methods are available to determine soluble Sianalysis for liquid and solid Si fertilizers however soil is a dy-namic entity which unfortunately is understudied in Si researchTubana et al (2014) reported that the amount time and durationof release of plant-available Si from added silicate slag (12 Si)determined by the 05 M acetic acid extraction procedure were in-fluenced by clay and organic matter content of the soil They usedsoils from Indiana Louisiana Michigan Mississippi and Ohiothat varied in soil pH (50ndash74) organic matter content (03ndash50) and texture (fine sandy loam to silty clay) with initialplant-available Si ranging from 22 to 165 mg kgminus1 Increases inplant-available Si were seen 30 days after application across all


soil types However different trends were observed following thisrelease of plant-available Si (a) a drastic decline throughout the120-day period was observed for soils containing high sand andclay fractions presumably due to leaching and adsorption respec-tively and (b) continuously increased up to 90 days after applica-tion then declined for silt loamndashtextured soil containing moderateamounts of organic matter Across all soils 120 days after applica-tion the level of plant-available Si was found to remain substan-tially higher than the control (no Si added) A laboratoryincubation study was conducted by Babu et al (2014) to evaluatethe release pattern of H4SiO4 from wollastonite and Ca silicateslag (12 Si) applied to soils of Louisiana varying in clay contentand chemical properties They concluded that the amount ofH4SiO4 measured in solution (01 M NaCl) was influenced bythe adsorption capacity of soils which was highly determinedby soil pH organic matter and clay content

SynthesisThe establishment of Si fertilization as an agronomic practice

in crop production is perceived to be pursued only in regionswhere there is lack of sufficient supply of plant-available Si Per-haps the oldest reason justifying fertilization in agricultural landswas a compelling circumstance related to sugarcane production in

wwwsoilscicom 13


the geologically old soils of Hawaii and the organic and sandysoils of the south Florida EAA The overwhelming published liter-ature about the beneficial contributions of Si fertilization to cropproductivity in production areas where disease and insect pressureis high and abiotic stresses are present has prompted research onSi to proliferate in the United States in the 1990s (Datnoffet al 2001)

The principal crops in US agriculture collectively can take up955 million tons Si in shoots annually (Table 2) or remove asmuch as 111 million tons from the soils planted to these crops(Table 3) The estimated amount of Si taken up in a given areaby each crop showed that removal rates of Si from the soil canbe substantial and even higher than primary essential nutrients(eg P K) especially for rice (329 kg Si haminus1) sugarcane(160 kg Si haminus1) and wheat (108 kg Si haminus1) These crops are clas-sified as highndashSi-accumulating plants From the limited informa-tion collected in this review it appears that the estimated shoot Siuptake is significantly much higher (1408 kg haminus1) than the restof the crops in the list even though this crop is a dicotyledonwhich are considered to be lowndashSi-accumulating plants Theshoot Si used in the computation was based on the research ofDraycott (2006) indicating that sugar beet top dry matter can con-tain as much as 115 g Si kgminus1 Nevertheless the estimated amountof Si removed annually by these crops is generally substantial andfaster than in natural ecosystems Based on the total cropland areain the United States (USDA-NASS 2007) and the average plantSi (Bazilevich 1993) the total amount of Si removed annuallyis approximately 211 million tons This is about 10 of theworldannual Si removal rate by crops of 210 to 224 million tons re-ported earlier (Bazilevich 1993 Reimers 1990 Savant et al1997a) The amount of plant-available Si in solution is character-ized as low ranging from 01 to 16 kg Si haminus1 in the upper 20-cmsoil layer this is either due to the desilication (leaching) processcommon in highly weathered soils (Oxisols Ultisols) or simplydue to the fact that the solubility of most Si-bearing minerals insoils is low The replenishment of plant-available Si in soil solu-tion is critical and may be characterized as slow based on soil Sidissolution kinetics and Si release from organic sources includingcrop residues and burned rice husk The latter however was re-ported to have long-term positive effects Faimon (1998) studiedthe kinetics of release of Si from feldspar grandiorite and am-phibolite revealing solutions can attain supersaturation with re-spect to Si consequently this may lead to Si flowing out fromthe solution forming secondary minerals or their amorphousequivalent This process essentially reduces the amount ofplant-available Si

Silicon chemical dynamics in soils have been understudieduntil recently The research thus far reveals that the chemical dy-namics between Si andmany soil components influence the amountof plant-available Si released to soil solution This could challengethe assumption that based on the amount of 21 layered silicateclay minerals that most soils in the United States are capable ofsupplying high concentrations of plant-available Si to crops A re-cent study showed a significant increase in grain yield of rice evenwhen grown on a soil rich in 21 layered silicate clays with highinitial levels of 05 M acetic acidndashextractable Si at 160 μg gminus1

(Tubana et al 2014) Babu et al (2014) pointed out that the re-lease of H4SiO4 to soil solution is critical to the amount of soil so-lution plant-available Si and is influenced by different processes(eg desorption polymerization) and soil properties other thanpH This explained the unexpected response to Si of rice grownon soil despite high initial Si level and clay content In this con-text the need for Si fertilization not only may be justified by hav-ing low plant-available Si but also could be based on the soilrsquosability to replenish the Si removed by plants from the soil solution

14 wwwsoilscicom

especially for soils under continuous intensive farming systemsClearly a soilrsquos clay content pH organic matter content and Aland Fe oxide content are essential factors to consider when mak-ing a recommendation for a Si fertilizer

The success of US agriculture as an industry has been attrib-uted to modernization and adoption of intensive crop farming ap-proaches that have enabled the country to become a net exporterof food (USDA-ERS 2013) This trend is likely to continue andso will the removal of Si from US cropland soils Climate changeis foreseen to bring more challenges and limitations to crop produc-tion in the forms of higher disease pressure drought waterloggedconditions and salt stress In addition continuous cropping is al-ways accompanied by removal of basic cations and fertilizationwhich in turn will eventually lead to soil acidification making lim-ing programs indispensable in crop production to secure maximumyield For all these reasons Si fertilization using low-cost industrialbyproduct sources with high liming potential may become an agro-nomic practice in many crop production systems in the UnitedStates especially for the purpose of alleviating biotic and abioticstresses that may limit yields as well as for correcting soil pH

ACKNOWLEDGMENTPublished with the approval of the Director of the Louisiana

Agricultural Experiment Station as publication 2016-306-27516

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Agostinho F L Datnoff J RabasseMMartins and B Tubana 2014 Effect ofsilicon sources on grain yield and silicon accumulation of rice grown underdifferent phosphorus rate In ASA-CSSA-SSSA International AnnualMeetings November 2ndash5 2014 Long Beach CA

Alvarez J and L Datnoff 2001 The economic potential of silicon for inte-grated management and sustainable rice production Crop Prot 2043ndash48

Anderson D L and J E Bowen 1990 Sugarcane Nutrition Potash and Phos-phate Institute Atlanta GA

Anderson D L D B Jones and G H Snyder 1987 Response of arice-sugarcane rotation to calcium silicate slag on Everglades HistosolsAgron J 79531ndash535

Ayres A S 1966 Calcium silicate slag as a growth stimulant for sugar cane onlow-silicon soils Soil Sci 101216ndash227

Babu T L Datnoff J Yzenas and B Tubana 2013 Silicon status of Louisianasoils grown to different field crops In ASA-CSSA-SSSA InternationalAnnual Meetings November 3ndash6 2013 Tampa FL

Babu T B Tubana L Datnoff JWang and J Yzenas 2014 Release pattern ofmonosilicic acid from different sources of silicon in soils of Louisiana InASA-CSSA-SSSA International Annual Meetings November 2ndash5 2014Long Beach CA

Basile-Doelsch I J D Meunier and C Parron 2005 Another continental poolin the terrestrial silicon cycle Nature 433399ndash402

Baylis A D C Gragopoulou K J Davidson and J D Birchall 1994 Effectsof silicon on the toxicity of aluminum to soybean Commun Soil Sci PlantAnal 25537ndash546

Bazilevich N I 1993 The Biological Productivity of North Eurasian Ecosys-tems RAS Institute of Geography Moscow Nayka pp 293

Bazilevich N I L E Rodin and N N Rozov 1975 The biological productiv-ity and cycle of chemical elements in plant associations In Biosphere Re-source ser1 Bazilevich N I (ed) Leningrad pp 5ndash33



Beacutelanger R R N Benhamou and J G Menzies 2003 Cytological evidence ofan active role of silicon in wheat resistance to powdery mildew(Blumeria graminis f sp Tritici) Phytopathology 93402ndash412

Blecker S W R L McCulley O A Chadwick and E F Kelly 2006 Biolog-ical cycling of silica across a grassland bioclimosequence Global BiogeoCycles 201ndash11

Bollard E G and G W Butler 1966 Mineral nutrition of plants Annu RevPlant Physiol 1777ndash112

Bollich P K C R Robichaux D E Groth J H Oard and P F Bell 2001 Siliconuse in Louisiana rice Potential improvements in disease management andgrain yields In Silicon in Agriculture Vol 8 Studies in Plant ScienceDatnoff L E G H Korndorfer and G H Snyder (eds) AmsterdamThe Netherlands Elsevier 387

Brecht M O L E Datnoff T A Kucharek and R T Nagata 2004 Influenceof silicon and chlorothalonil on the suppression of gray leaf spot andincrease plant growth in St Augustine grass Plant Dis 88338ndash344

Brown R C 2003 Biorenewable ResourcesmdashEngineering New Products fromAgriculture Iowa State Press Ames IA

Breuer J 1994 Hartsetzende Bouml den Nordkameruns In PhD thesis Soil ScienceDepartment Technical University of Munich Weihenstephan pp 189

Brunings A M L E Datnoff J F Ma N Mitani Y Nagamura BRathinasabapathi and M Kirst 2009 Differential gene expression of ricein response to silicon and rice blast fungus Magnaporthe oryzae AnnAppl Biol 155161ndash170

Buck G B G H Korndorfer and L E Datnoff 2011 Extractors for estimat-ing plant available silicon from potential silicon fertilizer sources J PlantNutr 34274ndash282

Carpita N C 1996 Structure and biogenesis of the cell walls of grasses AnnuRev Plant Physiol Plant Mol Biol 47445ndash476

Carreacute-Missio V F A Rodrigues D A Schurt S C Pereira M G A Oliveiraand L Zambolim 2009 Ineficiecircncia do siliacutecio no controle da ferrugem docafeeiro em soluccedilatildeo nutritive Trop Plant Pathol 34416ndash421

Carver T L R J Zyen and G G Ahlstrand 1987 The relationship betweeninsoluble silicon and success or failure of attempted primary penetrationby powdery mildew (Erysiphe graminis) germlings on barley PhysiolMol Plant Pathol 31133ndash148

Chain F C Cocircteacute-Beaulieu F Belzile J G Menzies and R R Beacutelanger 2009A comprehensive transcriptomic analysis of the effect of silicon on wheatplants under control and pathogen stress conditions Mol Plant Microbe In-teract 221323ndash1330

Chen C H and J Lewin 1969 Silicon as a nutrient element for Equisetumarvense Can J Bot 7125ndash131

Cheong W Y and P Halais 1970 Needs of sugarcane for silicon when grow-ing in highly weathered latosols Exp Agric 699ndash106

Cheacuterif M N Benhamou J G Menzies and R R Beacutelanger 1992a Silicon in-duces resistance in cucumber plants against Pythium ultimum PhysiolMol Plant Pathol 41411ndash425

Cheacuterif M J G Menzies N Benhamou and R R Beacutelanger 1992b Studies ofsilicon distribution in wounded and Pythium ultimum Physiol Mol PlantPathol 41371ndash385

Cheacuterif M A Asselin and R R Beacutelanger 1994 Defense responses induced bysoluble silicon in cucumber roots infected by Pythium spp Phytopathology84236ndash242

Clements H F E W Putman R H Suchisa G I N Yee and M L Wehling1974 Soil toxicities as causes of sugarcane freckle Macadamea leaf chlo-rosis (Keaau) and Maui sugar cane growth failure Hawaii Agr Expt StaTech Bull No 88

Clements H F 1964 Interaction of factors affecting yield Annu Rev PlantPhysiol 15409ndash442

Clements H F 1965a The roles of calcium silicate slag in sugar cane growthReps Hawaiian Sugar Tech 25103ndash126

Clements H F 1965b Effects of silicate on the growth and freckle of sugar canein Hawaii Porto Rico Proc Int Soc Sugar Cane Technol 12197ndash215


Cloyd R A 2009 Are silicon-based fertilizer applications ldquoreallyrdquo effectiveagainst insect pests FloriBytes 31ndash9

Colman S M and D P Dethier 1986 An overview of rates of chemicalweathering In Rates of Chemical Weathering of Rocks and Minerals Col-man SM and D P Dethier (eds) Academic Press Orlando FL pp 1ndash18

Conley D J 2002 Terrestrial ecosystems and the global biogeochemical silicacycle Global Biogeochem Cy 161121

Conner S D 1921 Liming in its relation to injurious inorganic compounds inthe soil J Amer Soc Agron 13113ndash124

Cornelis J T B Delvauz R B Georg Y Lucas J Ranger and S Opfergelt2011 Tracing the origin of dissolved silicon transferred from varioussoil-plant systems towards rivers A review Biogeosciences 889ndash112

Cotterill J V R W Watkins C B Brennon and D P Cowan 2007 Boostingsilica levels in wheat leaves reduces grazing by rabbits Pest Manag Sci63247ndash253

Dadkhah A R and H Grrifiths 2006 The effect of salinity on growth inor-ganic ions and dry matter partitioning in sugar beet cultivars J AgricSci Technol 8199ndash210

Dann E K and S Muir 2002 Peas grown in media with elevatedplant-available silicon levels have higher activities of chitinases and β-13-glucanase are less susceptible to a fungal leaf spot pathogen and accumu-late more foliar silicon Australas Plant Pathol 319ndash13

Datnoff L E G H Snyder R N Raid and D B Jones 1991 Effect of cal-cium silicate on blast and brown spot intensities and yields of rice PlantDis 75729ndash732

Datnoff L E CW Deren and G H Snyder 1997 Silicon fertilization for dis-ease management of rice in Florida Crop Prot 16525ndash531

Datnoff L E and G H Snyder 1994 Comparison of silicon and benomylalone and in combination for reducing blast incidence Biol Cultural TestsControl Plant Diseases 9113

Datnoff L E G H Snyder and G H Korndoumlrfer 2001 Silicon in agricultureVol 8 Studies in plant science Elsevier Amsterdam The Netherlands

Datnoff L E G H Snyder and C W Deren 1992 Influence of silicon fertil-izer grades on blast and brown spot development and on rice yields PlantDis 761011ndash1013

Datnoff L E F A Rodrigues and KW Seebold 2009 Silicon and Plant Dis-ease In Mineral Nutrition and Plant Disease Datnoff L E W H Elmerand D M Huber (eds) The American Phytopathological Society PressSt Paul MN pp 233ndash246

Deren C W L E Datnoff and G H Snyder 1992 Variable silicon content ofrice cultivars grown on Everglades Histosols J Plant Nutr 152363ndash2368

Deren C W L E Datnoff G H Snyder and F G Martin 1994 Silicon con-centration disease response and yield components of rice genotypes grownon flooded organic Histosols Crop Sci 34733ndash737

Desplanques V L Cary J C Mouret F Troland G Bourrieacute O Grauby and JD Meunier 2006 Silicon transfers in a rice field in Camargue (France) JGeochem Explor 88190ndash193

Draycott A P 2006 Sugar beet World Agriculture Series Blackwell Publish-ing pp 444

Drees L R L PWilding N E Smeck and A L Senkayi 1989 Silica in soilsQuartz and disorders polymorphs In Minerals in Soil Environments SoilScience Society of America Madison pp 914ndash974

Elawad S H and V E Green Jr 1979 Silicon and the rice plant environmentA review of recent research Il Riso 28235ndash253

Elawad S H G J Gascho and J J Street 1982 Response of sugarcane to sil-icate source and rate I Growth and yield Agron J 74481ndash484

Elliott C L and G H Snyder 1991 Autoclave-induced digestion for the col-orimetric determination of silicon in rice straw J Agric Food Chem391118ndash1119

Eneji A E S Inanaga SMuranaka J Li P An T Hattori andW Tsuji 2005Effect of calcium silicate on growth and dry matter yield of Chloris gayanaand Sorghum sudanense under two soil water regimes Grass Forage Sci60393ndash398

wwwsoilscicom 15


Epstein E 1999 Silicon Annu Rev Plant Physiol Plant Mol Biol50641ndash664

Epstein E 1994 The anomaly of silicon in plant biology Proc Natl Acad SciU S A 9111ndash17

Epstein E and A Bloom 2005Mineral Nutrition of Plants Principles and Per-spectives (2nd ed) Sinauer Associates Sunderland MA

Faimon J 1998 The kinetics of the release of silicon and aluminum from alumi-nosilicates into aqueous mildly acid solutions Scripta Fac Sci Nat UnivMasaryk Brun (Brno Czeck Rep) 2559ndash68

FAOSTAT 2014 Top productionmdashWorld (total) in 2012 Retrieved in Dec 222014 Available online at httpfaostatfaoorgsite339defaultaspx

Fauteux F W Reacutemus-Borel J G Menzies and R R Beacutelanger 2005 Siliconand plant disease resistance against pathogenic fungi FEMS MicrobiolLett 2491ndash6

Fawe A M Abou-Zaid J G Menzies and R R Beacutelanger 1998Silicon-mediated accumulation of flavonoid phytoalexins in cucumberPhytopathology 88396ndash401

Fawe A J G Menzies M Cheacuterif and R R Beacutelanger 2001 Silicon and dis-ease resistance in dicotyledons In Silicon in Agriculture Datnoff L EG H Snyder and G H Korndoumlfer (eds) Elsevier Amsterdam TheNetherlands pp 159ndash170

Feng X S Wu A Wharmby and A Wittmeier 1999 Microwave digestion ofplant and grain standard reference materials in nitric and hydrofluoric acidsfor multi-elemental determination by inductively coupled mass spectrome-try J Anal Atos Spectrom 14939ndash946

Fox R L and J A Silva 1978 Symptoms of plant malnutrition Silicon an ag-ronomically essential nutrient for sugarcane Illust Conc Trop Agric No8 Dept Agron Soil Sci College of Trop Agric amp Human Res Univ ofHawaii Honolulu HI

Fox R L J A Silva O R Younge D L Plucknett and G D Sherman 1967Soil and plant silicon and silicate response by sugarcane Soil Sci Soc AmProc 31775ndash779

Foy C D 1992 Soil chemical factors limiting plant growth Adv Soil Sci1997ndash149

Foy C D R L Chaney and M C White 1978 The physiology of metal tox-icity in plants Annu Rev Plant Physiol 29511ndash566

Frantz J M J C Locke L E Datnoff M Omer A Widrig D Sturtz LHorst and C R Krause 2008 Detection distribution and quantifica-tion of silicon in floricultural crops utilizing three distinct analyticalmethods Comm Soil Sci Plant Anal 392734ndash2751

Fraysse F O S Pokrovsky J Schott and J D Meunier 2006 Surface proper-ties solubility and dissolution kinetics of bamboo Phytoliths GeochimCosmochim Ac 701939ndash1951

Fraysse F O S Pokrovsky J Schott and J D Meunier 2009 Surface chemis-try and reactivity of plant phytoliths in aqueous solutions Chem Geol258197ndash206

French-Monar R F A Rodrigues G H Korndoumlfer and L E Datnoff 2010Silicon suppresses Phytophthora blight development on bell pepper JPhytopathol 158554ndash560

Gascho G J 2001 Silicon sources for agriculture In Silicon in Agricul-ture Vol 8 Studies in plant science Datnoff L E G H Snyder andG H Koumlrndorfer (eds) Amsterdam The Netherlands Elsevier197ndash207

Gascho G J and G H Korndoumlrfer 1998 Availability of silicon from severalsources determined by chemical and biological methods In Soil ScienceSociety of America Annual Meeting Baltimore MD pp 18ndash22 308

Ghareeb H Z Bozsoacute G P Ott C Repenning F Stahl and K Wydra2011 Transcriptome of silicon-induced resistance against Ralstoniasolanacearum in the silicon non-accumulator tomato implicates prim-ing effect Physiol Mol Plant Pathol 7583ndash89

Gong H Z K Chen SWang and C Zhang 2005 Silicon alleviates oxidativedamage of wheat plants in pots under drought Plant Sci 169313ndash321

16 wwwsoilscicom

Halligan J E 1912 Soil Fertility and Fertilizers Reprint 2013 ForgottenBooks London pp 4ndash5

Hallmark C T L P Wilding and N E Smeck 1982 Methods of Soil Analy-sis Part 2 Chemical and Microbiological Properties 15263ndash274

Harley A D and R J Gilkes 2000 Factors influencing the release of plant nu-trient elements from silicate rock powders A geochemical overview NutrCycl Agroecosyst 5611ndash36

Hassuani S J M R L V Leal and I C Macedo 2005 Biomass power gen-eration Sugar cane bagasse and trash CTCPNUD Piracicaba SP Brazilpp 270

Hattori T S Inanaga H Araki P An SMorita M Luxuva and A Lux 2005Application of silicon enhanced drought tolerance in Sorghum bicolorPhysiol Plant 123459ndash466

Hawley G C 2004 Wollastonite Mining Engineering 5652ndash54

Hayasaka T H Fujii and K Ishiguro 2008 The role of silicon in preventingappressorial penetration by the rice blast fungus Phytopathology981038ndash1044

Haynes R J O N Belyaeva and G Kingston 2013 Evaluation of industrialwastes as sources of fertilizer silicon using chemical extractions and plantuptake J Plant Nutr Soil Sci 176238ndash248

Haysom M B C and L S Chapman 1975 Some aspects of the calcium sil-icate trials at Mackay Proc Aust Sugar Cane Technol 42117ndash122

HaysomM B and Z A Ostatek-Boczynski 2006 Rapid wet oxidation proce-dure for the estimation of silicon in plant tissue Comm Soil Sci PlantAnal 372299ndash2306

Heckman J R S Johnston and W Cowgill 2003 Pumpkin yield and diseaseresponse to amending soil with silicon HortScience 38552ndash554

Heckman J 2012 Silicon and Soil Fertility The Soil Profile 201ndash12 Availableonline at httpsnjaesrutgersedupubssoilprofilesp-v20pdf

Heath M C and M A Stumpf 1986 Ultrastructural observation of penetrationsites of the cowpea rust fungus in untreated and silicon-depleted French beancells Physiol Mol Plant Path 2927ndash39

Hodson M J P J White A Mead and M R Broadley 2005 Phylogeneticvariation in the silicon composition of plants Ann Bot 961027ndash1046

Hogendorp B K R A Cloyd and J M Swiader 2012 Determination ofsilicon concentration in some horticultural plants HortScience471593ndash1595

HoubenD P Sonnet and J Cornelis 2014 Biochar fromMiscanthus A poten-tial silicon fertilizer Plant Soil 374871ndash882

Huang C H P D Roberts and L E Datnoff 2011 Silicon suppresses Fusar-ium crown and root rot of tomato J Phytopathol 159546ndash554

Hurney A P 1973 A progress report on the calcium silicate investigationsProc Aust Sugar Cane Technol 40109ndash113

Imaizumi K and S Yoshida 1958 Edaphological studies on silicon supplyingpower of paddy soils Bull Natl Inst Agric Sci B 8261ndash304

Inal A D J Pilbeam and A Gunes 2009 Silicon increases tolerance to borontoxicity and reduces oxidative damage in barley J Plant Nutr 32112ndash128

Industrial Minerals 1999 Wollastonite Industrial Minerals No 379 April p 19

Janislampi KW 2012 Effect of silicon on plant growth and drought toleranceUSUAll Graduate Theses and Dissertations Paper 1360 Available on-lineat httpdigitalcommonsusueduetd1360

Jones R L 1969 Determination of opal in soil by alkali dissolution analysisSoil Sci Soc Am Proc 33976ndash978

Jones L H P and K A Handreck 1965 Studies of silica in the oat plant IIIUptake of silica from soils by plant Plant Soil 2379ndash96

Jones L H P and K A Handreck 1967 Silica in soils plants and animalsAdv Agron 19107ndash149

Kalapathy U A Proctor and J Shultz 2002 An improved method for produc-tion of silica from rice hull ash Bioresour Technol 85285ndash289

Kamenidou S T J Cavins and S Marek 2009 Evaluation of Si as a supple-ment for greenhouse zinnia production Sci Hort 119297ndash301



Kamenidou S 2002 Silicon supplementation affects greenhouse produced cutflowers MS thesis Oklahoma State University Stillwater OK

Keeping M G O L Kvedaras and A G Bruton 2009 Epidermal silicon insugarcane Cultivar differences and role in resistance to sugarcane borerEldana saccharina Environ Exp Bot 6654ndash60

Khalid R A J A Silva and R L Fox 1978 Residual effects of calcium sili-cate in tropical soils II Biological extraction of residual soil silicon SoilSci Soc Am J 4294ndash97

Knight C T G and S D Kinrade 2001 A primer on the aqueous chem-istry of silicon In Silicon in Agriculture Vol 8 Studies in Plant ScienceDatnoff L E G H Snyder and G H Korndoumlrfer (eds) Amsterdam TheNetherlands Elsevier 57ndash84

Kobayashi NMMorioka T Komiyama T Ito andM Saigusa 2008 Siliconcontent in livestock manure compost and a simple estimation method for it(in Japanese with English summary) J Japan Soc Waste Mgt Experts19150ndash154

Korndoumlrfer G H M N Coelho G H Snyder and C T Mizutani 1999Avaliaccedilatildeo de meacutetodos de extraccedilatildeo de siliacutecio para solos cultivados com arrozde sequeiro Rev Bras Ci Solo 23101ndash106

Korndoumlrfer G H G H Snyder M Ulloa G Powell and L E Datnoff 2001Calibration of soil and plant silicon analysis for rice production J PlantNutr 241071ndash1084

Kraska J E and G A Breitenbeck 2010a Simple robust method for quanti-fying silicon in plant tissue Comm Soil Sci Anal 412075ndash2085

Kraska J E and G A Breitenbeck 2010b Survey of the silicon status offlooded rice in Louisiana Agron J 102523ndash529

Lanning F C T L Hopkins and J C Loera 1980 Silica and ash content anddepositional patterns in tissues of mature Zea mays L plants Ann Bot45549ndash554

Latshaw W L 1924 Elemental composition of corn plant J Ag Research27845ndash860

Laruelle G G V Roubeix A Sferratore B Brodherr and D Ciuffa 2009Anthropogenic perturbations of the silicon cycle at the global scaleKey role of the land-ocean transition Global Biogeochem Cycles 23GB4031Leningrad 5ndash33

Lemes E C L Mackowiak A Blount J J Marois D L Wright L Coelhoand L E Datnoff 2011 Effects of silicon applications on soybean rust de-velopment under greenhouse and field conditions Plant Dis 95317ndash324

Lewin J and B E F Reimann 1969 Silicon and plant growth Annu RevPlant Physiol 20289ndash304

Li Q F C C Ma and Q L Shang 2007 Effects of silicon on photosynthesisand antioxidative enzymes of maize under drought stress Ying Yong ShengTai Xue Bao 18531ndash536

Liang Y H Hua Y Zhu J Zhang C Cheng and V Romheld 2006 Impor-tance of plant species and external silicon concentration to active silicon up-take and transport New Phytol 17263ndash72

Liang Y C T S Ma F S Li and Y J Feng 1994 Silicon availability and re-sponse of rice and wheat to silicon in calcareous soils Soil Sci Plant Anal252285ndash2297

Liang Y W Sun Y Zhu and P Christie 2007 Mechanisms of silicon-mediatedalleviation of abiotic stresses in higher plants A review Environ Pollut147422ndash428

Lindsay W L 1979 Chemical Equilibria in Soils Wiley Interscience New York

Lipman C B 1938 Importance of silicon aluminum and chlorine for higherplants Soil Sci 45189ndash198

Lux A M Luxovaacute S Morita J Abe and S Inanaga 1999 Endodermal silic-ification in developing seminal roots of lowland and upland cultivars of rice(Oryza sativa L) Can J Bot 77955ndash960

Ma J F S Goto K Tamai and M Ichii 2001 Role of root hairs and lateralroots in silicon uptake by rice Plant Physiol 1271773ndash1780

Ma J F N Mitani S Nagao S Konishi K Tamai T Iwashita and M Yano2004 Characterization of the silicon uptake system and molecular mappingof the silicon transporter gene in rice Plant Physiol 1363284ndash3289


Ma J F and E Takahashi 2002 Soil Fertilizer and Plant Silicon Research inJapan Elsevier Science Dordrecht The Netherlands

Ma J F K Tamai N Yamaji NMitani S KonishiMKatsuharaM IshiguroY Murata and M Yano 2006 A silicon transporter in rice Nature440688ndash691

Ma J F N Yamaji N Mitani K Tamai S Konishi T FujiwaraM Katsuharaand M Yano 2007 An efflux transporter of silicon in rice Nature448209ndash212

Makabe S K Kakuda Y Sasaki T Ando H Fujii and H Ando 2009 Rela-tionship betweenmineral composition or soil texture and available silicon inalluvial paddy soils on the Shounai Plain Japan Soil Sci Plant Nutr55300ndash308

Marschner H 1995 Beneficial Mineral Elements In Mineral Nutrition ofHigher Plants (2nd ed) Academic Press London pp 405ndash434

Marxen A T Klotzbuumlcher R Jahn K Kaiser V S Nguyen A Schmidt MSchaumldler and D Vetterlein 2016 Interaction between silicon cycling andstraw decomposition in a silicon deficient rice production system PlantSoil 398153ndash163

Matichencov V V and E A Bocharnikova 2001 The relationship between sil-icon and soil physical and chemical properties In Silicon in AgricultureVol 8 Studies in Plant Science Datnoff L E G H Snyder and G HKorndoumlrfer (eds) Amsterdam The Netherlands Elsevier 209ndash219

Matichenkov V V D V Calvert and G H Snyder 1999 Silicon fertilizers forcitrus in Florida Proc Fla State Hort Soc 1125ndash8

Maxim L D R Niebo S LaRosa B Johnston K Allison and E EMcConnell 2008 Product stewardship in wollastonite production InhalToxicol 201199ndash1214

Maxwell W 1989 Lavas and Soils of the Hawaiian Islands Hawaiian SugarPlantersrsquo Association Honolulu Hawaii pp 189

McCray J M and RMylavarapu 2010 Sugarcane nutrient management usingleaf analysis Florida Cooperative Extension Service Pub SS-AGR-335httpedisifasufleduag345

McCray J M P R Newman R W Rice and I V Ezenwa 2011 Sugarcaneleaf tissue sample preparation for diagnostic analysis Florida CooperativeExtension Service Pub SS-AGR-259 httpedisifasufledusc076

McKeague J A andM G Cline 1963 Silica in soil solutions I The form andconcentration of dissolved silica in aqueous extracts of some soils Can JSoil Sci 4370ndash82

Mehlich A 1984 Mehlich 3 soil test extractant A modification of Mehlich 2extractant Comm Soil Sci Plant Anal 151409ndash1416

Meunier J D F Guntzer S Kirman and 2008 Terrestrial plant-Si and envi-ronmental changes Mineral Mag 72263ndash267

Meunier J D 2003 Le rocircle des plantes dans le transfert du silicium agravela surfacedes continents CR Geosci 3351199ndash1206

Meyer J H and M G Keeping 2005 The impact of nitrogen and siliconnutrition on the resistance of sugarcane varieties to Eldana saccharina(Lepidoptera Pyralidae) Proc S Afr Sug Technol Ass 79363ndash367

Meyer J H and M G Keeping 2001 Past present and future research of therole of silicon for sugar cane in southern Africa In Silicon in AgricultureVol 8 Studies in Plant Science Datnoff L E G H Snyder and G HKorndoumlrfer (eds) Amsterdam The Netherlands Elsevier 257ndash275

Mitani N and J F Ma 2005 Uptake system of silicon in different plant spe-cies J Exp Bot 561255ndash1261

Monger H C and E F Kelly 2002 Silica minerals In Soil Mineralogy WithEnvironmental Applications Soil Science Society of America MadisonUSA pp 611ndash636

Moore P 2003 Changing tracks Industrial Minerals No 43269ndash73

Narayanaswamy C and N B Prakash 2009 Calibration and categorization ofplant available silicon in rice soils of south India J Plant and Nutr321237ndash1254

National Resources Conservation Service 2014 Soil Extent Mapping ToolAccessed on January 2 2015 at httpwwwceipsuedusoiltoolsemtoolhtml

wwwsoilscicom 17


Nonaka K and K Takahashi 1988 A method of measuring available silicatesin paddy soils Jpn Agric Res Q 2291ndash95

Norton L D G E Hall N E Smeck and J M Bigham 1984 Fraginap bond-ing in a late-Wisconsian loss-derived soil in East-Central Ohio Soil SciSoc Am J 481360

Novozamsky I R van Eck and V J G Houba 1984 A rapid determination ofsilicon in plant material Commun Soil Sci Plant Anal 15205ndash212

Paces T 1983 Rate constants of dissolution derived from the measurements ofmass balance in hydrological catchments Geochim Cosmochim Acta471855ndash1863

Park C S 2001 Past and future advances in silicon research in the Republic ofKorea In Silicon in Agriculture Vol 8 Studies in plant science DatnoffL E G H Snyder and G H Korndorfer (eds) Amsterdam TheNetherlands Elsevier 351ndash371

Pilon-Smits E A C F Quinn W Tapken M Malagoli and M Schiavon2009 Physiological functions of beneficial elements Current Opinion inPlant Biol 12267ndash274

RaghupathyB 1993 Effect of lignite fly ash on rice Int RiceRes Notes 1827ndash28

Raleigh G J 1939 Evidence for the essentiality of silicon for growth of the beetplant Plant Physiol 14823ndash828

Raven J A 1983 The transport and function of silicon in plants Biol Rev58179ndash207

Reidinger S MH Ramsey and SE Hartley 2012 Rapid and accurate analy-ses of silicon and phosphorus in plants using a portable X-ray fluorescencespectromete New Phytol 195669ndash706

Reimers N F 1990 Natural uses Dictionary-reference book Moscow Misl

Renard K G G R Foster G A Weesies D K McCool and D C Yoder1997 Predicting soil erosion by water A guide to conservation planningwith the Revised Universal Soil Loss Equation (RUSLE) In US Depart-ment of Agriculture Handbook 703 US Government Printing OfficeWashington DC

Richmond K E and M Sussman 2003 Got silicon The non-essential bene-ficial plant nutrient Curr Opin Plant Biol 6268ndash272

Rizwan M J Meunier H Miche and C Keller 2012 Effect of silicon on re-ducing cadmium toxicity in durumwheat (Triticum turgidum L cv ClaudioW) grown in a soil with aged contamination J Hazard Mater 209ndash210326ndash334

Rodrigues F A L E Datnoff G H Korndorfer K W Seebold and M CRush 2001 Effect of silicon and host resistance on sheath blight develop-ment in rice Plant Dis 85827ndash832

Rodrigues F A N Benhamou L E Datnoff J B Jones and R R Beacutelanger2003 Ultrastructural and cytochemical aspects of silicon-mediated riceblast resistance Phytopathology 93535ndash546

Rodrigues F A L J Dallagnol H S S Duarte and L E Datnoff 2015a Sil-icon control of foliar diseases in monocots and dicots In Silicon and PlantDisease Rodrigues F A and L E Datnoff (eds) Springer InternationalPublishing Switzerland pp 67ndash108

Rodrigues F A D J McNally L E Datnoff J B Jones C Labbeacute NBenhamou J G Menzies and R R Beacutelanger 2004 Silicon enhancesthe accumulation of diterpenoid phytoalexins in rice A potential mecha-nism for blast resistance Phytopathology 94177ndash183

Rodrigues F AWM Jurick L E Datnoff J B Jones and J A Rollins 2005Silicon influences cytological and molecular events in compatible and in-compatible rice-Magnaporthe grisea interactions Physiol Mol PlantPathol 66144ndash159

Rodrigues F A R S Resende L J Dallgnol and L E Datnoff 2015b Siliconpotentiates host defense mechanisms against infection by plant pathogensIn Silicon and Plant Disease Rodrigues F A and L E Datnoff (eds)Springer International Publishing Switzerland pp 109ndash138

Sauer D and W Burghardt 2000 Chemical processes in soils on artificial ma-terials Silicate dissolution occurrence of amorphous silica and zeolites InProceedings of First International Conference on Soils of Urban IndustrialTraffic and Mining Areas Essen 1 pp 339ndash346

18 wwwsoilscicom

Sauer D and W Burghardt 2006 The occurrence and distribution of variousforms of silica and zeolites in soils developed from wastes of iron produc-tion Catena 65247ndash257

Sauer D L Saccone D J Conley L Herrmann and M Sommer 2006 Re-view of methodologies for extracting plant-available and amorphous Sifrom soils and aquatic sediments Biogeochem 8089ndash108

Savant N K L E Datnoff and G H Snyder 1997a Depletion ofplant-available silicon in soils A possible cause of declining rice yieldsCommun Soil Sci Plant Anal 281145ndash1152

Savant N K G H Snyder and L E Datnoff 1997b Silicon Management andSustainable Rice Production Adv Agron 58151ndash199

Schachtschabe I P and C G Heinemann 1967 Wasserlo sliche Kieselsa urein Lo szligbo den Z Pflanzenern Bodenk 11822ndash35

Schulthess C P and Y Tokunaga 1996 Metal and pH effects on adsorption ofpoly (vinilalcohol) by silicon oxide Soil Sci Soc Am J 6092

Sebastian D 2012 Silica SLV Results presented at the Association ofAmerican Plant Food Control Officials Lab Services Committee MeetingSan Antonio TX 2012 httpwwwaapfcoorgmeetings_aapfcohtml(accessed May 8 2012)

Sebastian D H Rodrigues C Kinsey G Korndoumlrfer H Pereira G Buck LDatnoff S Miranda and M Provance-Bowley 2013 A 5-day method fordetermination of soluble silicon concentrations in nonliquid fertilizer mate-rials using a sodium carbonate-ammonium nitrate extractant followed byvisible spectroscopy with heteropoly blue analysis Single-laboratoryvalidation J AOAC International 96251ndash258

Seebold KW Jr 1998 The influence of silicon fertilization on the developmentand control of blast caused byMagnaporthe grisea (Hebert) Barr in uplandrice PhD Dissertation Univ Fla 230

Seyfferth A and S Fendorf 2012 Silicate mineral impacts on the uptake andstorage of arsenic and plant nutrients in rice (Oryza sativa L) Environ Sciand Tech Am Chem Soc 4613176ndash13183

Shaw B T H Thomas and D T Cooke 2002 Responses of sugar beet(Beta vulgaris L) to drought and nutrient deficiency stress PlantGrowth Regul 3777ndash83

Sidhu J K M J Stout D C Blouin and L E Datnoff 2013 Effect of siliconsoil amendment on performance of sugarcane borer Diatraea saccharalis(Lepidoptera Crambidae) on rice Bull Entomol Res 103656ndash664

Silva J A 1973 Plant mineral nutrition In Yearbook of Science and Technol-ogy McGraw-Hill Co New York NY p 338ndash340

Smis A FJA Murguzur E Struyf EM Soininen JGH Jusdado P Meireand KA Brathen 2014 Determination of plant silicon content with nearinfrared reflectance spectroscopy Front Plant Sci 5(496)1ndash9

Snyder G H 1991 Development of a silicon soil test for Histosol-grown riceIn EREC Res Rpt EV-1991-2 University of Florida BelleGlade

Snyder G H 2001 Methods for silicon analysis in plants soils and fertilizerIn Silicon in Agriculture Datnoff L E G H Snyder and G HKorndoumlrfer (eds) Elsevier Science BV New York pp 185ndash207

SnyderGH D B Jones andG J Gascho 1986 Silicon fertilization of rice onEverglades Histosols Soil Sci Soc Am J 501259ndash1263

Snyder G H V V Martichenkov and L E Datnoff 2007 Silicone In Hand-book of Plant Nutrition Barker A V and D J Pilbean (eds) CRC Taylorand Francis New York USA pp 551ndash568

Soil Survey Staff 1999a Soil Taxonomy The Twelve Soil Orders 2nd EditionNatural Resources Conservation Service US Department of Agriculture

Soil Survey Staff 1999b Soil Taxonomy A basic system of soil classificationfor making and interpreting soil surveys 2nd edition Natural ResourcesConservation Service US Department of Agriculture Handbook 436

Sommer A L 1926 Studies concerning the essential nature of aluminum andsilicon for plant growth Univ Calif Publ Agri Sci 557ndash81

Sommer M D Kaczorek Y Kuzyahov and J Breuer 2006 Silicon pools andfluxes in soils and landscapesmdashA review J Plant Nutr Soil Sci169310ndash329



Song Z H Wanh P J Strong and S Shan 2014 Increase of available siliconby Si-rich manure for sustainable rice production Agron Sustain Dev34813 doi101007s13593-013-0202-5

Summer M D B M Jenkins P R Hyde J F Williams R G Mutters S CScardacci and MW Hair 2003 Biomass production and allocation in ricewith implications for straw harvesting and utilization Biomass Bioenerg24163ndash173

Sun L and K Gong 2001 Silicon-based materials from rice husks and theirapplications Ind Eng Chem Res 405861ndash5877

Svendrup H 1990 The Kinetics of Base Cation Release Due to ChemicalWeathering Lund University Press Lund Sweden

Taber H G D Shogren and G Lu 2002 Extraction of silicon from plant tis-sue with dilute HCl and HF and measurement by modified inductivecoupled argon plasma procedures Commun Soil Sci Plant Anal331661ndash1670

Takahashi E J F Ma and Y Miyake 1990 The possibility of silicon as essen-tial element for higher plants Comments Agric Food Chem 299ndash122

Takahashi K 1981 Effect of slags on the growth and the silicon uptake by riceplant and the available silicates in paddy soil Bull Nat L Shikoku AgricExp Stn 3875ndash114

Treacuteguer P DM Nelson A J van Bennekom D J DeMaster A Leynaert andB Queacuteguiner 1995 The silica balance in the world ocean A reestimateScience 268375ndash379

Tubana B C Narayanaswamy J Lofton Y Kanke M Dalen and L Datnoff2012 Impact of silicon fertilization to sugarcane grown on alluvial soils inLouisiana J Am Soc Sugar Cane Tech 3275

Tubana B M Kongchum L Datnoff and T Babu 2013 Effect of siliconsources on rice biomass silicon uptake and grain yield In ASA-CSSA-SSSA International Annual Meetings Tampa FL pp 3ndash6 2013

Tubana B L Datnoff C Narayanaswamy B White T Babu and J Yzenas2014a Changes on plant-available silicon level of selected soils from theMidwest and South USA applied with different rates of silicate slag In6th International Conference on Silicon in Agriculture StockholmSweden pp 2014

Tubana B W Paye T Babu P Dupree B White S Chanda M Dalen SMaia MMartins and D Harrell 2014b Impact of silicate slag fertilizationon grain yield silicon accumulation and plant essential nutrient content ofrice In ASA-CSSA-SSSA International Annual Meetings Long BeachCA pp 2ndash5 2014

Tubana B T and J R Heckman 2015 Silicon in soils and plants In Siliconand Plant Disease Rodrigues F A and L E Datnoff (eds) Springer Inter-national Publishing Switzerland pp 7ndash51

USDA Economic Research Service 2013 Latest US Agricultural Trade DataEd StephenMacDonald USDA 4 Sept 2013Web 28 Sept 2013 lthttpwwwersusdagovdata-productsforeign-agricultural-trade-of-the-united-states-(fatus)latest-us-agricultural-trade-dataaspxUkckR_Pn-M8gt

USDA National Agricultural Statistic Service 2015 Crop Production 2014Summary Accessed April 22 2016 at httpwwwusdagovnassPUBSTODAYRPTcropan15pdf

USDA National Agricultural Statistic Service 2007 Census of AgricultureAvailable at httpwwwagcensususdagovPublications2007Full_Re-portindexasp

Vasanthi N L M Saleena and S A Raj 2012a Silicon in day today lifeWorld Appl Sci J 171425ndash1440

Vasanthi N D Chandrasekeran and S A Raj 2012b Phytosil as an alternativecarrier to talc for biocontrol agents In Proc Natl Symp Recent AdvBioinoculatns Techn Agricultural College amp Research Institute Madurai

Velvel M A 1986 The mathematical basis for determining rates of geo-chemical and geomorphic processes in small forested watersheds by


mass balance Examples and implications In Rates of ChemicalWeathering of Rocks and Minerals Colman S M and D P Dethier(eds) Academic Press Orlando FL pp 349ndash451

Viator H J Richard and G Williams 2004 The response of LCP 85ndash384to silicate slag application LSU AgCenter Sugar Research StationAnnual Report 2004

Virta R L 2004 WollastonitemdashUS Geological Survey Minerals Year-book 821ndash3

van Bockhaven J L Spichal O Novak M Strand T Asano S Kikuchi MHofte and D de Vleesschauwer 2014 Silicon induces resistance to brownspot fungus Cochliobolus miyabeanus by preventing the pathogen fromhijacking the rice ethylene pathway New Phytol 206761ndash773

Vivancos J C Labbeacute J G Menzies and R R Beacutelanger 2015Silicon-mediated resistance of Arabidopsis against powdery mildew in-volves mechanisms other than the salicylic acid (SA)-dependent defensepathway Mol Plant Pathol 16572ndash582

Wagner F 1940 Die Bedeutung der Kieselsaumlure fuumlr das Wachstum einigerKulturpflanzen ihren Naumlhestoffhaushalt und ihre Anfaumllligkeit gegen echteMehtaupilze Phytopathol Z 12427ndash479

Wallace A 1993 Participation of silicon in cation-anion balance as possiblemechanism for aluminum and iron tolerance in some gramineae J PlantNutr 16547ndash553

Wang J J S K Dodla and R E Henderson 2004 Soil silicon extractabilitywith seven selected extractants in relation to colorimetric and ICP determi-nation Soil Sci 169861ndash870

Wedepohl K H 1995 The composition of the continental crust GeochimCosmochim Acta 591217ndash1239

White A F 1995 Chemical weathering rates of silicate minerals in soils InWhite A F and SL Brantley (eds) Chemical Weathering Rates of SilicateMinerals Rev Min 31407ndash461

White B H Mascagni Jr P Dupree T Babu and B Tubana 2014 Effect ofvarying rates of silicon and nitrogen fertilizer on grain yield yield compo-nents and nutrient uptake of wheat ASA-CSSA-SSSA International An-nual Meetings Long Beach CA

Williams D E and J Vlamis 1957 The effect of silicon on yield andmanganese-54 uptake and distribution in the leaves of barley plants grownin culture solutions Plant Physiol 32404ndash409

Williams D E and J Vlamis 1967 Manganese and silicon interaction in theGramineae Plant Soil 27131ndash140

Williams L A and D A Crerar 1985 Silica diagenesis II General mecha-nisms J Sed Pet 55312ndash321

Woolley J T 1957 Sodium and silicon as nutrients for the tomato plantPlant Physiol 32317ndash321

Xu G X Zhan L Chunhua S Bao X Liu and T Chu 2001 Assessingmethods of available silicon in calcareous soils Commun Soil Sci PlantAnal 32787ndash801

Yeo A R S A Flowers G Rao KWelfare N Senanayake and T J Flowers1999 Silicon reduces sodium uptake in rice (Oryza sativa L) in saline con-ditions and this is accounted for by a reduction in the transpirational bypassflow Plant Cell Environ 22559ndash565

Yoshida S D A Forno J H Cook and KA Gomes 1976 Routine procedurefor growing rice plants in culture solution In Laboratory Manual for Phys-iological Studies of Rice (3rd ed) The International Rice Research Insti-tute Los Banos Laguna Philippines pp 61ndash65

Yoshida S Y Ohnishi and K Kitagishi 1962 Chemical forms mobility anddeposition of silicon in the rice plant Soil Sci Plant Nutr 8107ndash111

Zippicotte J 1881 Fertilizer US Patent no 238240 Official Gazetter of theUnited States Patent Office 19 9 and 496

wwwsoilscicom 19

FIG 1 Top 10 produced crops in the world in 2012 Seven of thesecrops are classified as Si accumulators (gt10 Si in dry matter)The values inside the bar are the reported shoot Si content byHodson et al (2005)


commonly present in carbonaceous rocks such as limestones andcarbonites whereas rocks such as basalt and orthoquartzite con-tain high concentrations of Si (23ndash47) (McKeague andCline 1963 Wedepohl 1995 Monger and Kelly 2002) Thechemicalweathering of silicate-containing minerals is the ultimatesource of dissolved Si (as monosilicic acid H4SiO4) which con-tributes to continental soil formation through linked biogeochem-ical reactions (Basile-Doelsch et al 2005) Silicon release to soilsolution from weathering of silicate-containing minerals is ratherslow and is governed by precipitation and neoformation ofauthigenic Si constituents Si adsorptiondesorption on varioussolid phases uptake and assimilation by vegetation and microor-ganisms preservation of stable Si forms in the profile and addi-tion from external atmospheric inputs (Cornelis et al 2011)These are linked processes and the largest interpool Si transfertakes place between biomass (biogenic silica from phytolithsand microorganisms) and soil solution (dissolved Si in the formof H4SiO4) at rates ranging from 17 to 56 1012 kg Si yminus1

(Conley 2002) In the ocean the largest interpool Si transfer

FIG 2 Different fractions of Si in soils Adapted fromTubana andHeckmaSo in order to publish this adaptation authorization must be obtained bothe owner of copyright in the translation or adaptation A color version

2 wwwsoilscicom

is between biogenic silica from diatoms and dissolved Si at67 1012 kg Si yminus1 (Treacuteguer et al 1995 Matichencov andBocharnikova 2001) Laruelle et al (2009) estimated that theamount Si transformed into biogenic silica averages 25 1012 kg yminus1

Silicon in soils is grouped into liquid adsorbed and solidphase fractions The composition of these fractions of Si com-pounds in the soil is presented in Fig 2 (Matichencov andBocharnikova 2001 Sauer et al 2006) The solid Si phase con-sists of poorly crystalline and microcrystalline amorphous andcrystalline forms of Si The largest solid phase fraction of Si oc-curs in crystalline forms mainly as primary and secondary sili-cates and silica materials Amorphous solid phase Si originatesfrom either as biogenic (originating from plant residues and re-mains of microorganisms) or lithopedogenic (Si complexes withAl Fe heavy metals and soil organic matter) materials(Matichencov and Bocharnikova 2001) The amount of amor-phous Si typically ranges from less than 1 to 30 mg gminus1 on a totalsoil basis (Jones 1969 Drees et al 1989) The solubility of Si inthe solid phase significantly affects the concentration of Si in theliquid phase Larger contribution is expected from amorphous sil-ica than quartz a crystalline silicate material The solubility ofamorphous Si ranges between 18 and 2 mM compared withquartzrsquos 010 to 025 mM Si (Drees et al 1989 Monger andKelly 2002) Biogenic silica also contributes to the concentrationof Si in soil solution and with solubility 17 times higher thanquartz this contribution to the dynamics of plant-available Si insoil solution is rather significant (Fraysse et al 2006) Both theliquid and adsorbed phase fractions of Si consist of H4SiO4 aswell as polysilicic acids and those dissolved Si complex with in-organic and organic compounds The silicic acid occurring as mo-nomeric (H4SiO4) is the plant-available form of soil SiPolymerization a process by which monomeric units of silicicacid form a chain results in the formation of polymeric silica orhigh-molecular-weight silica (Williams and Crerar 1985) UnlikeH4SiO4 polysilicic acid has not been shown to be plant-availablehowever it can link soil particles through the creation of silicabridges which improve soil aggregation andwater-holding capac-ity (Norton et al 1984) The liquid Si and adsorbed Si along with

n (2015) Adaptations are themselvesworks protectedby copyrightth from the owner of the copyright in the original work and fromof this figure is available in the online version of this article

















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6 wwwsoilscicom





ShootBiomasspound

ShootSiβ




693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts


vested area








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Authordagger


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11073967Bazilevich 1993 21101250




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8 wwwsoilscicom














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10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19
















wwwsoilscicom 3

















4 wwwsoilscicom















wwwsoilscicom 5






Crops







6 wwwsoilscicom





ShootBiomasspound

ShootSiβ




693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts


vested area








Crop












Authordagger


tons


11073967Bazilevich 1993 21101250




wwwsoilscicom 7





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19

















4 wwwsoilscicom















wwwsoilscicom 5






Crops







6 wwwsoilscicom





ShootBiomasspound

ShootSiβ




693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts


vested area








Crop












Authordagger


tons


11073967Bazilevich 1993 21101250




wwwsoilscicom 7





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19













wwwsoilscicom 5






Crops







6 wwwsoilscicom





ShootBiomasspound

ShootSiβ




693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts


vested area








Crop












Authordagger


tons


11073967Bazilevich 1993 21101250




wwwsoilscicom 7





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19






Crops







6 wwwsoilscicom





ShootBiomasspound

ShootSiβ




693 182 126059 9930781 136a 4209964 1291764 151 26 683 48948 417 395173 329933 154 143648 62

12704 139 1765738 592918 234dagger 682886 1408

384 151 57966 1608753 245 2144278 108

9552395 107b

eets etc)

ts


vested area








Crop












Authordagger


tons


11073967Bazilevich 1993 21101250




wwwsoilscicom 7





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19






Crop












Authordagger


tons


11073967Bazilevich 1993 21101250




wwwsoilscicom 7





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19





8 wwwsoilscicom














wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19










wwwsoilscicom 9





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















wwwsoilscicom 13






14 wwwsoilscicom



































































wwwsoilscicom 15























16 wwwsoilscicom













































































wwwsoilscicom 17























18 wwwsoilscicom

































































wwwsoilscicom 19





10 wwwsoilscicom



TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








12 wwwsoilscicom








Source

Silicon Content



















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TABLE

4Extractio

nProc

edures

forEstim

atingPlan

t-Av

ailableSiBo

thin

SoilSo

lutio

nan

dAd

sorbed

Phase

Solution

Procedu

reSilicon

Fractions

References

H2O

10gin

50mL+01

NaN

3to

reduce

biologicalactivity

incubate

21datroom

temperaturewith

manualshaking

2tim

esaday

Water

soluble


10gin

100mL4

-hshaking

Water

soluble

Foxetal1967K

halid

etal1978

10gin


for2wk

Water

soluble


10gin

100mL1

-hshaking

Water

soluble


CaC

l 2001

MCaC

l 21

-gsamplein

20-m

Lsolutio

n16-h

shaking

Liquidphasereadily

available

Haysom

andChapm

an1975

001

MCaC

l 21

0-gsamplein

100mLsolutio

n1-hshaking

Liquidphasereadily

available


Naacetate+

aceticacid

018

NNaacetate+087


pH4

10-g

samplein

100mLsolutio



Imaizumiand

Yoshida1958

018

NNaacetate+087


pH4

10-g

samplein

100-mLsolutio

n1-hshaking



NH4acetate


topH

45ndash48with

01M

aceticacid1

-gsamplein

20-m

Lsolutio

n1-hshaking


Ayre1966C

heongandHalais1970


topH

48with

01M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



Acetic

acid

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshakingwith

12hresting


Snyder1991

05M

aceticacid1

-gsamplein

10-m

Lsolutio

n1-hshaking



05M

aceticacid1

0-gsamplein

25-m

Lsolutio

novernightrestin

g+2-hshaking


Snyder2001

Citricacid

01M

citricacid1

-gsamplein

50-m

Lsolutio

n2-hshaking

restingovernight+

1-hshaking


Acquaye

andTinsley1964

Nacitrate+NaH

CO3

80

03M

Nacitrate+20

1M

NaH

CO32

-gsamplein

50-m

Lsolutio

n5min

at80degC


sesquioxidesurfaces

Breuer1994

NH4citrate

1M

NH4citrate10-g

samplein

25-m

Lsolutio

n80-h

shaking



H2SO4

0005M

H2SO41

-gsamplein

200-mLsolutio

n16-h

shaking


Hurney1973

Mehlich-3

2gsoilin


n5-min

shaking


Mehlich1984

Adapted

from

Tubana

andHeckm

an(2015)A

daptations

arethem

selvesworks

protectedby

copyrightSo



bothfrom

theow

nerofthe

copyright


theow

nerof


adaptation








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Source

Silicon Content



















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A Review of Silicon in Soils and Plants and Its Role in US ...planttuff.com/wp-content/.../A_Review_of_Silicon_in... · Silicon in soils is grouped into liquid, adsorbed, and solid