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Boron fertilizers: use, mobility in soils and uptake by plants Fien Degryse Fertilizer Technology Research Centre
Boronfertilizers:use,mobilityinsoilsanduptakebyplants
FienDegryseFertilizerTechnologyResearchCentre
Borontoxicityanddeficiencyinplants
§ Boronisanessentialmicronutrientrequiredforseveral
functionsinplants,particularlyforcellwallsandfor
reproduction(flowering)
§ Uptakebyplantsispassiveandunregulated,sotoxicitycaneasilyoccur
§ Bisrelativelyimmobileinmostplantspecies,socropsare
adverselyaffectedbyevenshort-termdeficiencies
University of Adelaide
Btoxicity
www.acpfg.com.au
Bdeficiency
Bdeficiency
www.extension.umn.edu www.agric.wa.gov.au
Borontoxicityanddeficiencyinplants
§ ThewindowbetweendeficiencyandtoxicityforBisverynarrow,e.g.
§ Theoptimalrangeinsoilvariesbycrop,butisroughly0.5-5
mg/kghotwater-extractableboronformostspecies
University of Adelaide
Guptaetal1985,CanJSoilSci65:381
Borontoxicityanddeficiencyinplants
§ SpeciessensitivetoBdeficiency:legumes,Brassica,fruittrees
§ SpeciessensitivetoBtoxicity:– Severalcerealspecies(barley,wheat)(duetolowpectincontent?)
– Stoneandpomefruits
University of Adelaide
Shorrocks1997,PlantSoil193:121
Boroninsoil
§ TotalBconcentrationsinsoildependonparentmaterialandthe
degreeofweathering,withnaturalbackgroundconcentrations
usuallyrangingfrom2to100mg/kg(average∼20mg/kg;Power
&Woods1997)
§ Boronisneverfoundasasingleelementandisusuallyfound
combinedwithoxygenasborates
§ Boronmayalsobetightlyboundinsilicatemineralstoproduce
veryinsolubleminerals,e.g.claymineralsortourmalines
§ Adsorptiononoxidesandassociationwithorganicmatteroccurs
University of Adelaide
Boroninsoil
§ SolubleBinsoilexistsasaneutralspecies,H3BO3,inmost
soilsoralsoasB(OH)4-inhighpHsoils(pKa=9.2)
§ TheadsorptionofBinsoilsisweak,thoughgenerallyhigherinhighpHsoils(pH>8)
DatafromGoldbergetal2000,SSSAJ64:1356
0.1
1
10
100
1 10 100
Kd
(l/kg
)
CEC (cmolc/kg)
pH 9pH 7
Boroninsoil
§ ThelowretentionmakesBvulnerabletoleaching
⇒ExcessrainfallcanresultinlossofappliedBfromthetop
layer
University of Adelaide
0
5
10
15
20
25
30
0 0.5 1
Depth(in
ches)
HWB(mg/kg)
w3
w26
w52
DatafromWinsor1951,SoilSci71:91 Communar&Keren2005,SSSAJ69:311
Boroninsoil
AreaswhereBdeficiencyismostlikelytooccur
University of Adelaide
Shorrocks1997,PlantSoil193:121
Boroninsoil
§ ToxicBlevelsaremostlikelytooccurindryareas,particularlyin:
– soilsinherentlyhighinB
– soilsirrigatedwithB-richirrigationwater
§ HighBisoftenfoundinassociationwithsalinityproblems
§ ThehighestBconcentrationsareoftenfoundatdepth(>20cm),sotopsoilsamplingmaynotrevealtheissue
§ “Detoxifying”thesoilthroughexcessirrigationisoftennotpracticaloreconomical,soselecting/breedingcropcultivarswithtoleranceisusuallytheonlypracticalapproachto
increaseormaintainyieldsonhigh-BsoilsUniversity of Adelaide
Boroninsoilandplants-Summary
§ Boronishighlymobileinsoil(ifnotoccludedinminerals/
organicmatter)
§ Borondeficiencyismostcommonlyfoundinhumidregions,
asleachingremovesplant-availableB
§ ThereisanarrowrangebetweenBdeficiencyandtoxicity,withoptimalsoilconcentrationsgenerallybetween0.5-5mg/
kghot-waterextractableB
§ ThesensitivitytoBdeficiencyortoxicityisplantspeciesdependent
University of Adelaide
Boronfertilizer-Sources
§ BoronisprimarilyobtainedfromminedBminerals,located
mostlyinaridregionsofTurkeyandtheUSA,andalsoin
Argentina,Chile,Russia,China,andPeru
§ Approximately70%oftheworldsupplycomesfromtwo
corporateorganizations–EtiMineWorks(Turkey)andRio
Tinto(USBorax)
§ ItisestimatedthatTurkeyhas72%oftheworld’sBreserves
University of Adelaide
Boronfertilizer-Sources
§ Solubleborates/boricacid(boraxandrefinedborates)
University of Adelaide
Compound(Common/commercialname) Formula %B
Disodiumtetraboratedecahydrate(Borax,tincal) Na2B4O7.10H2O 11.3
Disodiumtetraboratepentahydrate(Fertibor,Granubor) Na2B4O7.5H2O 15.2
Disodiumoctaboratetetrahydrate(Solubor,Granubor) Na2B8O13.4H2O 20.9
Anhydrousborax(Dehybor) Na2B4O7 21.5
Boricacid H3BO3 17.5
Boronfertilizer-Sources
§ Crushedorrefinedores
University of Adelaide
Compound Formula %B
Colemanite Ca2B6O11.5H2O 15.8
Ulexite NaCaB5O9.8H2O 13.3
UlexiteColemanite
Boronfertilizer-Sources
§ Othersparinglysolublecompounds
– Boronfritsareproducedbymeltingsilicateswithboratesand
haveverylowsolubility
– Boronphosphateissynthesizedfromboricacidandphosphoric
acidanditssolubilitydependsonthetemperatureofsynthesis
(Abatetal.2014)University of Adelaide
Compound Formula %B
Boronfrits (boricoxideglass) 2-11
Boronphosphate BPO4 10.2
Boronfertilization
§ RecommendedratesdependonBcroprequirementsand
generallyrangefrom0.25to3kg/ha
§ Methodsofapplication:
– Soilapplication:mostlybroadcast,bandingnotrecommended
becauseoftoxicityrisk
– Foliarforselectedcrops
University of Adelaide
Boronfertilization-Foliar
§ Boronisphloem-mobileinsorbitol-richspecies,e.g.severalfruitcrops
§ Inmostspecies,Bisnotphloem-mobileandhencefoliarfertilizationisnoteffective
University of Adelaide
Brown&Hu1998,BetterCrops82:28Brownetal1999,PlantPhys119:17
WildType Transgenic
Boronfertilization
§ RecommendedratesdependonBcroprequirementsand
generallyrangefrom0.25-3kg/ha
§ Methodsofapplication:
– Soilapplication:mostlybroadcast,bandingnotrecommended
becauseoftoxicityrisk
– Foliarforselectedcrops
§ Typesofsoil-appliedfertilizer:– GranularfertilizerbulkblendedwithgranularNPKsources
– BoronatedNPKfertilizer
University of Adelaide
§ Bulkblendingresultsinpoorerfielddistributionandhencehigherriskoftoxicity/deficiencythanco-granulatedfertilizers
Boronfertilization–Bulkblendvsboronated
University of Adelaide
Co-granulated
Bulkblend
daSilvaetal,inpreparation7days
Co-granulatedproduct Bulkblend
62days
Co-granulatedproduct Bulkblend
IssueswithsolubleBfertilizer
§ SolubleBmaycausetoxicityinitiallywithsensitivecrops
§ RetentionofBinmostsoilsisnegligible,soBleacheseasily,
whichmayresultindeficiencylaterintheseason
University of Adelaide
Highconcentrationsmaycausetoxicity
Lowconcentrationsmayresultindeficiency
Leachingloss
Slowreleasefertilizers
§ Slowreleasefertilizerreducetheriskofbothleachinglosses(possiblyresultingindeficiency)andofseedlingtoxicity
§ Thereleaseshouldbeslowenoughtoprotectagainstleachingandharmfulconcentrations,butfastenoughto
supplythenutrientswithinareasonabletimeframe
University of Adelaide
Slowreleasefertilizers–Reducedleaching
Lessleachingforcoarse
colemanite
⇒AvailableBmaintainedat
optimallevelsoverlonger
period
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60
HWBinto
p6in(mgkg
-1)
Time(weeks)
borax
finecolemanite
coarsecolemanite
Winsor1951,SoilSci71:99
0
5
10
15
20
25
30
0 0.5 1
Depth(in
ches)
HWB(mg/kg)
w3
w26
w52
0
5
10
15
20
25
30
0 0.5 1
Depth(in
ches)
HWB(mg/kg)
w3
w26
w52
CoarsecolemaniteBorax
Slowreleasefertilizers–Reducedtoxicity
Seedlingtoxicitytest(Abatetal.2015)
§ Petridishfilledwithsoil
§ Fertilizergranule(MAPorMOPwith2%B)incentre
§ Seedsgerminatedundercontrolledconditions(23/15°C,day/
night)
§ Picturestaken7and11daysaftergerminationandprocessed
usingimaginganalysissoftware(GIMP)
University of Adelaide
50gmoistenedsoil10gmoistenedsoiland1gseeds
Fertilisergranule(MAP:30mg,MOP:40mg)
Slowreleasefertilizers–Reducedtoxicity
ToxicityandHWBconcentrationsaroundMAP/MOP+2%Bgranules
University of Adelaide Abatetal.2015,PlantSoil391:153
Borax=Ulex.=>Colem.*>BPO4(500)>BPO4(800)
Borax=Ulex.>Colem.=BPO4(500)>BPO4(800)
*ColemanitemoresolubleduetoCappt(Caphosphates)andlowerpHaroundMAP
Slowreleasefertilizers–Moreoptimalnutrientsupply
Pottrial(Abatetal.2015)
§ Sandyacidsoilwithlowhot-waterBconcentration(0.2mg/
kg)
§ FiveBsources:borax,ulexite,colemanite,BPO4(500)and
BPO4(800)co-granulatedwithMAPat1%B
§ Canolagrownfor12weeksin1-kgpots
§ After3months,leachingwith1400mlofwater,andsecond
canolacrop(12weeks)grown
§ Yieldandtissueanalysis
University of Adelaide
Slowreleasefertilizers–Moreoptimalnutrientsupply
University of Adelaide Abatetal.2015,SSSAJ79:97
Firstcrop Secondcrop
BoraxUlex.
Colem.
BPO4(500)
BPO4(800)MAP
BoraxUlex.
Colem.
BPO4(500)
BPO4(800)MAP
Slowreleasefertilizers–Moreoptimalnutrientsupply
University of Adelaide
§ Withmostsolublesources,toxicitysymptomsandyield
reductioninfirstcrop
Abatetal.2015,SSSAJ79:97
Slowreleasefertilizers–Moreoptimalnutrientsupply
University of Adelaide
§ Withmostsolublesources,toxicitysymptomsandyield
reductioninfirstcrop
§ Withmostsolublesources(boraxandulexite),
deficiencysymptomsinsecondcrop
Abatetal.2015,SSSAJ79:97
Conclusions§ Boronisanunchargedionandisnotstronglyretainedinsoils§ Boronisthereforeverymobileanddeficienciesaremost
commoninhighrainfallenvironments,especiallyonsandy
soils
§ The‘window’betweendeficiencyandtoxicityisnarrowforB,socareisneededinfertilizerformulationandplacementto
avoidBtoxicity
§ OnlysmallamountsofBarerequiredtoalleviatedeficiency(~0.5-3kg/ha)
Conclusions§ DuetopoorspatialdistributionofB,bulkblendscontainingB
saltsarelesseffectivethanco-granulatedproducts
§ TheuseofhighlysolubleBsourcescanresultinleachinglossesinhighrainfallenvironments,andalsoposesahigherriskoftoxicity
§ Slowreleasesourceshavemostpotentialtosupplyadequate
Bthroughouttheentireplantcycleormultiplecropcycles
Acknowledgments
University of Adelaide www.adelaide.edu.au/fertiliser
Organizers(DrCakmak)andsupportinginstitutions(Boren)
MikeMcLaughlinMargaretAbatRoslynBairdRodrigoCoquidaSilvaBogumilaTomczakColinRiversAshleighBroadbent
Issueswithsolubleboronfertilizers-ToxicityThank You
