Making more effective zinc fertilizers · Slide 8 Life Impact The University of Adelaide Pure Zn...

Making more effective zinc fertilizers

Mosaic-supported Fertilizer Technology Research Centre @ The University of Adelaide, Australia

Life Impact The University of Adelaide Slide 1

Zinc is an essential element for humans

l  Humans,animals,plantsneedzinctofunction

l  Affectsover300enzymesinthebody

l  Supportsnormalgrowthanddevelopment

l  Essentialformetabolismandcellulargrowth

l  Especiallyimportantduringpregnancy,childhoodandadolescence

l  Keyforimmunesystem

l  Activateswoundhealingl  Impactstaste,mood,hair,fingernails


Zinc deficiency – a global Issue

l  2billionpeopleatriskofzincdeficiency

l  195millionchildren<5yearsatriskofstunting

l  2millionchildren<5yearsdieduetopneumonia

l  1.5millionchildren<5yearsdieduetodiarrhea

l  800,000deathsattributedtozincdeficiency

l  450,000children<5yearsdieduetozincdeficiency

l  Subclinicalzincdeficiencyalsoprevalentindevelopednations


l  TheInternationalZincAssociation(IZA)incollaborationwithUNICEFhasaprogramtosupplementchildren’sdietswithZn

l  IZAisalsosupportingpromotionofzinc-fortifiedfertilizersindeficientareas

Zinc is an essential element for humans


Zinc nutrition of crops

l CropsrequireZninsmallamountstopromotephotosynthesis,seedproduction,growthregulationandforresistancetodisease

l DeficiencyofZnisaglobalproblemthataffectssoilsandcropsworldwide

l ThecrucialroleZnplaysinhumanhealthisnowrecognisedasaglobalissue


Zn

Zn

Zn

Zn Zn

l highCaCO3l highpHl highclaycontentl highFeandAloxidesl lowsoilmoisture

Zn

SOIL

LimitedZnuptake

What limits crop Zn uptake from soils? FertilizerZn

SoilSolutionZn2+

ZnCO3

ZnCO3

Zn3(PO4)2

AdsorbedZnPrecipitatedZn


Zinc nutrition of crops TherearetwomainfactorstoconsiderincropZnnutrition

l  Placement-physicalaccessibilityofZninsoilforaccessbycroprootsystems

l  Solubility-rateandextentofreleaseofZnfromfertilizertothegrowingcropinrelationtocropdemand


Zinc fertilizers

ZnOorZnSO4-enrichedNPKgranularfertilizerse.g.MAP,DAP,MESZ

GranularZnforbulkblendingwithNPKfertilizers

Znpowdersforfertigationorfoliar(commonlyZnOorZnSO4)

Znchelatesforfoliarorfertigation


Pure Zn fertilizers and solubility

l  ThemostsolubleZnsourceisZnsulfate,usuallysoldasZnsulfateheptahydrate(23%Zn)whichhasawatersolubilityof~960g/L

l  Zincoxide(ZnO)is80%Zn,buthasamuchlower(~200,000timeslower)watersolubility(1.5-5.0mg/L)thanZnsulfate

l  WhenZnOdissolvesithasanalkalinereaction(byconsumingacid)–asH+ionsareneededfordissolution,whichcausesitslowsolubility:

ZnO(solid)+2H+èZn2+(solution)+H2O



l  Despiteitslowwatersolubilityinwater,ZnOcanbeeffectiveifuniformlymixedthroughoutsoil

l  Thesoilprovidesa“pull”forZn,andcanstoppHincreasingaroundtheoxideparticleorprovideH+ions-allthesepromotedissolutionoftheoxide

l  However,ifZnOisbandedorpresentaslargeparticles,itseffectivenessisreducedcomparedtoZnSO4becauseofreducedsurfaceareafordissolution,thealkalinereactionandthelowerabilityofsoiltosorbtheZn



0

10

20

30

40

50

60

70

80

90

100

doubleband singleband surface uniform

PlantZ

nde

rived

from

fertilizer(%)

Placement

ZnO2

FP2

sulfate

e

f f

bc c

f

d

f

abababc aA

banded mixed


l  SegregationofpureZnfertilizersblendedwithothernutrients(e.g.N,P)resultsinpoordistributionofnutrientsinthefield

l  Granulessegregateaccordingtoparticlesizeratherthandensity

l  Particlesizesneedtobeidenticaltopreventgranulesegregation

Bulk blends of Zn with macronutrient fertilizers


Particlesizesegregationduringapplication



0

5

10

15

20

25

30

35

-2 -1 0 1 2

Distancefromtractorcentre(m)

Fertilizerd

istrib

ution(%

)

0.25-0.5mm

1-2mm

Granulesize

Source:Karnok(1986)TheSegregationofHomogeneousandBlendedGranularFertilizersfromaRotarySpreader,Agron.J.78:258-260

Ballisticsegregationfromrotaryspreaders



l TypicalratesofZnrequiredbycropsvaryfrom1to10kgZn/ha,generally2-3kg/ha

l AmountsofZnarelowandevenwithalowZncontentproducte.g.Znsulfateheptahydrate(23%Zn)thedistributionofZninsoilispoor

l Assumingnormalgranulesizeandbroadcastat2kg/ha,therewouldbeabout22Zngranules()persq.msoil

l Zincdoesnotdiffusefarfromthegranule–unlikelyplantrootswould“see”thisZneasily



l  Co-granulatedNP+Znproductsaretypically0.5-1%Znl  AssumingnormalgranulesizeandbroadcastZnat2kg/ha,

therewouldbeabout5001%Zngranulespersq.msoil–muchmorelikelyplantrootswould“discover”thisZn

l  AlsoaplacementadvantagethatZnisclosetoNandPnutrients–rootswill“gothere”

Co-granulated Zn with macronutrient fertilizers


l Co-granulatedproductsoffersignificantplacementadvantagesoverpureZnfertilizersorbulkblendsofZnfertiliserswithothernutrients

Co-granulated Zn with macronutrient fertilizers


Co-granulatedZn


FertilizerZnefficiencyislowinco-granulatedproducts

Ni62Cu63Zn64Cu65Zn66Zn67Zn68Ga69/int

INTENSITY

67Znenrichedplant

<0.5%ofaddedfertilizerZntakenupinfirstyear

McBeath T.M., McLaughlin M.J., Kirby J.K., Degryse F. (2013) A stable isotope methodology for measurement of soil applied zinc fertilizer recovery in Durum wheat (Triticum durum). Journal of Plant Nutrition and Soil Science (in press).

Chromosol

Kandosol

Calcarosol

Sodosol0.0

0.1

0.2

0.3

0 2 4 6 8 10 12 14

Fertilizere

fficien

cy(%

ofadd

ed)

LabilesoilZn(mgkg-1)

Znadded/Znuptake=115

Znadded/Znuptake=20


l  ThesolubilityoftherawZnmaterialsusedtoco-granulatewithphosphaticfertilizersisnotofgreatimportanceforfinalZnwatersolubility

l  Co-granulatingeitherZnsulfateorZnoxidewithNPfertilizersresultsinthesameformsofZninthefinalproduct–predominantlyZnphosphateorZnammoniumphosphate

Issues with co-granulating Zn in P fertilizers

3ZnO+2H3PO4⇔Zn3(PO4)2+3H2O

3ZnSO4+2H3PO4⇔Zn3(PO4)2+3H2SO4


Issues with co-granulating Zn in P fertilizers l Theacidityatwhichgranulationisperformed(measuredbypH)controlstherelativeamountsofeachoftheseminerals

l WehavemeasuredZnmineralsinMESZusingsynchrotronx-raymethods


l SpeciationofZninMicroessentialsandcompetitorgranules



l Inco-granulatedproducts,releaseofZnfromthegranuleislimitedinmostsoilsduetotheinsolubilityofZnphosphate

l AMAP+Zngranulewasincubatedinsoilfor4weeksandZnmappedinandaroundthegranuleusingsynchrotronradiation

90% of Zn remained in co-granulated MAP + Zn, 4 weeks after application to soil



l GranulechemistrycanaffecthowwatersolubleanddiffusibletheZnbecomesongranuledissolution


DAP+Zn MAP+S+Zn

GranulesplacedinsoilincentreofPetridishandmovementofZnfromgranuleevaluatedcolorimetrically


Speciation of Zn and granule pH


Water solubility of Zn and granule pH


Hopeite (Zn3(PO4)2) mineral controls Zn solubility

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

3 4 5 6 7 8

Totaldissolved

Zn(M

)

pH

0.01MMAP

0.1MMAP

ZAP

hopeite


Dissolution result

Rate of Zn release from granules


What about Zn in potash?


Agronomic effectiveness of Zn

R2 = 0.78

0

20

40

60

80

100

0 50 100Water soluble Zn (%)

Rel

ativ

e ag

rono

mic

ef

fect

iven

ess

(%)

ZnSO4ZnO

EarlyresearchfromMortvedtandGiordano(1969)demonstratedthathighwatersolubilityoffertilizerZnisneededforfast-growingannualcrops


Agronomic effectiveness of Zn l  WatersolubilityofZninthefertilizeristhekeyattribute

leadingtofertilizerefficiencyforannualcrops

l  ThelinkbetweenZnspeciesinthefertilizerandwatersolubilityisnotstrong

l  AkeyattributetocontrolisgranulepH

Low Medium High


Controlling granule pH

TypicalGranulationwindow(MAP)

MESZWindow


Increasing water soluble Zn in MESZ

l  NeedtoretainflexibilityinoperatingplantwindowforpHtoallowgoodgranulation

l  StrategiestoincreasewatersolubleZn

l  PhysicallyseparateZnfromPcoreofgranulewithcoatingspostgranulation

l  AddchelateseitherpriororpostgranulationtocomplexZnandreduceformationofhopeiteondissolution

l  Addacidifyingagentspostgranulationtoimprovesolubilityofhopeite


Barrier coatings to separate Zn from P

MAPgranule

Cu/Zncoating

“barrier”coating

USPOApplicationNumber61/309,894filed3March2010


Zinc effectiveness in barrier-coated products

K-Mag+PEI SOP+PEI

ZnSO4

Urea+PEI

Amm.Sul+PEI

MAP-Zn


Acidifying agents - products tested

PHOSPHATEFERTILISERSMESZwith1%Znwt/wtand2,3,4%acidcoatings

MOP-BASEDFERTILISERSAllwith1%Znwt/wtCompactedandCoated

MESZ+sulfamicacid MOPZnSO4

MESZ+oxalicacid MOPZnO

MESZ+citricacid MOPZnO+1.5%sulfamicacid

MESZ+peKacid MOP

MESZ(control)


Sulfamic acid coated MESZ

MESZwith

WSZn(%)

TotalZn(%)

WS/Total(%)

pH(1:10)

2%acid 0.71 1.07 66.6 3.88

3%acid 0.79 1.09 71.9 3.67

4%acid 0.91 1.13 81.1 3.49


Acidifying agents and Zn solubility

AcidifyingagentswereeffectiveinincreasingWSZn


Acidifying/chelating agents and Zn diffusion

AcidifyingagentsandEDTAwereeffectiveinincreasingZndiffusionfromgranules


Acidifying/chelating agents and Zn diffusion

CitricandsulfamicacideffectiveinincreasingZnsupplytoplantinadeficientsoil


Zn response curve

0.100 0.50 1 5

1 23 4

5

0.25 1042

1-1.5

54-4.5 5

CourtesyIsmailCakmak,SabanciUniversity


67.13MES10 67.1 67.4 67.3

12.5

2.5 - 3 33 -3.5

Score: 1 (bad) 5: very good

MESZuncoated

MESZ+SA2%

MESZ+OA2%

MESZ+SA4%



72.14 72.13 72.11 72.10

22 - 2.5 2.5 - 3

3.5 4

72.9


MAP+4%APP

MAP+2%APP

MAP+5%EDTA

MAP+2.5%EDTA

MAPuncoated



Co-compacted MOP products

MOP

WSZn(%)

TotalZn(%)

WS/Total(%)

pH(1:10)

1%ZnasZnSO41.14 1.17 98 5.79

1%ZnasZnO0.06 0.99 6 6.55

1%ZnasZnO+sulfamicacid 0.45 1.06 42 6.22CompactedMOP - -- 7.03


Acidifying/chelating agents and Zn diffusion - MOP

SulfamicacideffectiveinincreasingZndiffusionfromZnOaddedtoMOP.


Acidifying/chelating agents and Zn uptake - MOP


8 9 3 2

12

3 - 3.54

5

10


MOP MOP+ZnOcomp.

MOP+1%ZnSO4+0.1%PEI

MOP+ZnOcoat

MOP+ZnOcoat+1%SA



Keeping Zn water solubility in perspective

l  Fast-growingannualcrops(corn,wheat,soybean,canola,potato,etc.)intemperateanddrylandregionsrequirerapidZnsupplyfromsoil/fertilizer

l  Perennialcrops(fruit,stonefruit,nuts,forestry)inhighrainfallenvironmentsrequirealowerrateofZnsupplyfromsoil/fertilizeroveralongerperiod


Summary points

•  Zincmustbeaddedtoeachgranuletoensureuniformdistributioninthefield–bulkblendsnoteffective

•  HigherwatersolubleZnisdesirableforagronomicefficiencyofZnfertilizer

•  FormofZnaddedtoPfertilizersorpresentinfertilizerisnotimportantasZn-phosphatecompoundsformingranuleandin/aroundgranuleondissolution

•  GranulepHisastrongdeterminantofwatersolubilityandagronomicperformance

•  UsinggranulationpHtocontrolwatersolubilityofZnisdifficultasthegranulationpHwindowisthenrestricted


Summary points

•  WatersolubleZninPfertilizerscanbeimprovedbyaddingchelatesoracidifyingagentspostgranulation

•  ForMOPnoprecipitationofZnoccursin/onthegranuleandifasolubleZnsourceisused,dissolution/diffusionisrapid

•  Acidifyingagents(e.g.sulfamicacid)canbeaddedtoimproveeffectivenessofZnOinMOP

•  CoatingZnisbetterthanco-compaction•  SmallamountsofPEIincreasedeffectivenessofZnSO4with

MOP


Way forward

•  ContinuetosearchformoreeffectivechelatesoracidifyingagentsforimprovingwatersolubilityofZn

•  Seekgranulationaidstoallowawider(i.e.lower)pHwindowforeffectivegranulation

•  Evaluatepromisingformulationsinfieldtrials


Thank you for your attention! !

Making more effective zinc fertilizers · Slide 8 Life Impact The University of Adelaide Pure Zn...

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