养分含量 部分作物带走量.docx
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养分含量 部分作物带走量.docx
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养分含量部分作物带走量
Mehlich3ExtractionforMacro-andMicronutrients
HailinZhang,DavidHardy,RaoMylavarapu,andJimWang
ApplicationandPrinciple
Mehlich3(M3)estimatesplantavailabilityofmostmacro-andmicro-nutrientsonsoilsacidtoneutralpHusingadiluteacid-fluoride-EDTAsolutionofpH2.5.Themethodhasshowntobewellcorrelatedtocropresponsetofertilizerphosphorus(P)andapplicableforthedeterminationofextractablepotassium(K),calcium(Ca),magnesium(Mg),sodium(Na)andmicronutrients,suchasmanganese(Mn),iron(Fe),copper(Cu)andzinc(Zn).DuetothecorrosivenatureofchlorideintheMehlich2extractant(Mehlich,1978)anditsinabilitytoextractmicronutrientsonawiderangeofsoils,particularlycopperonorganicsoils,Mehlich3wasfirstimplementedinNorthCarolina’ssoiltestingprogramin1981,afterusingMehlich2fortwoyears.Dr.Mehlich’soverallgoalwastodevelopauniversalextractantthatwouldbeapplicableacrossawidespectrumofsoilsinregardtotheirreaction(pH)andmineralogy.Themethod(Mehlich,1984)wasofficiallypublishedafterMehlich’sdeathin1984,andhasbeenwidelyadoptedbymanylaboratoriesacrossthecountry.
Intheprocessofextraction,phosphorusissolubilizedunderdifferentmechanisms.Acidityofthetwoacids,nitricandacetic,increasesthesolubilityofironandaluminumphosphatesandextractsaportionofcalciumphosphatesifpresent.Fluorideservestocomplexaluminumcationsthatpotentiallybindwithphosphatestherebyincreasingthequantityoforthophosphateinsolution.AbenefitofaceticacidistokeepthesolutionbufferedbelowpH2.9topreventcalciumfluoridefromprecipitating.Ammoniumexchangeswithpotassium,calciumandmagnesiumandEDTAchelatesiron,manganese,zinc,andcopper.
PhosphorusandcationscanbedeterminedbyICP-AESinstrumentationsimultaneously.Phosphoruscontentinsolutioncanalsobedeterminedspectrophotometricallyatanacidityof0.20MH2SO4(Rodriguezetal.,1994)byreactingwithammoniummolybdateusingascorbicacidasareductantinthepresenceofantimony(MurphyandRiley,1962).However,differencesintheamountofPintheextracthavebeenfoundbetweenthetwoanalyticalmethods(Pittmanetal.,2005).
EquipmentandApparatus
1.Soilscoopcalibratedto2.0g(1.7cm3)andlevelingrod
2.60mLextractionbottles
3.Automaticsolutiondispenser
4.Reciprocatingshaker
5.ICP-AESand/orspectrophotometer,automatedFlowInjectionAnalysis(FIA)ifcolorimetricdeterminationofPisneeded
6.Reciprocatingsyringepumpcalibratedat20mL
Note:
Theoriginalpublishedmethod(Mehlich,1984)isstrictlyonavolumetricbasis(2.5ccsoil–25mLofextractant)makingnoassumptionsinsoilbulkdensity.Thepurposeofthisisduetothefactthatsoilscanvarysignificantlyindensities(0.5to1.7g/cc)anderroneousassumptionscanleadtolargeerrorsinfinalresultsobtained.
Reagents
SolutionsaremadewithASCreagentgradechemicalsanddistilledwaterunlessotherwisenoted.
1.Ammoniumnitrate(NH3NO3),fw=80.05,CAS#6484-52-2
2.Ammoniumfluoride(NH4F),fw=37.04,CAS#12125-01-8
3.Nitricacid(HNO3),68-70%,fw=63.02,15.5N,CAS#7698-37-2
4.Ethylenediaminetetraaceticacid(EDTA),(HOOCCH2)2NCH2CH2N(CH2COOH)2,fw=292.25,CAS#60-00-4
5.Aceticacid,glacial[CH3COOH]fw=60.05,CAS#64-19-7
6.Ammoniumfluoride-EDTAstocksolution(3.75MNH4F—0.25MEDTA):
Dissolve138.9gofNH4Fin600mLofdeionizedwaterandadd73.06gEDTA(or93.06gofNa2-EDTA•2H2O),dissolveanddiluteto1000mL.
7.Mehlich-3extractingsolution(0.2NCH3COOH—0.25NNH4NO3-0.015NNH4F-0.013NHNO3-0.001MEDTA@pH-2.50±0.05).Dissolve80.05gNH4NO3inabout3,000mLofdeionizedwater.Add16.0mLof3.75MNH4F-0.25MEDTAstocksolutionandmixwell.Add46mLofconcentratedglacialCH3COOHand3.3mLofconcentratedHNO3andbringto4,000mLfinalvolume.ThefinalpHshouldbe2.50±0.05.
8.CalibrationsStandards.Fromastandardsolutioncontaining1,000mgL-1oftheanalytesprepare1LofstandardsinMehlich3extractingsolutioncontainingthehighestconcentrationsofeachelement.Then,prepare250mLofothercalibrationstandardsfromdilutingthemostconcentratedone.Belowistherecommendedrangeofcalibrationstandards:
P
K
Ca
Mg
Na
Fe
Mn
Cu
Zn
B
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
0
0
0
0
0
0
0
0
0
0
10
10
20
10
10
10
2
2
2
2
25
25
50
25
25
25
5
5
5
5
50
50
100
50
50
50
10
10
10
10
Procedure
Extraction
1.Scooporweigh2.0±0.05gofairdriedsoilpulverizedtopass10meshsieve(<2.0mm)ina50-mLglassorplasticErlenmeyerflask.
2.Add20.0mLofMehlich3extractingsolution.Includeamethodblankandchecksamplesasdeterminedbythelab.
3.Placeextractionflask(s)onreciprocatingmechanicalshaker(200,4-cmrecips/minute)forfive(5)minutes.
4.Filtersuspensionimmediatelyandcollecttheextractin40mLplasticvials,refilteriffiltrateiscloudy.
Analysis
1.CalibratetheICPusingmultipleelementstandardsfollowingmanufacturer’srecommendationsintheoperationandcalibrationoftheinstrument.
2.Analyzingsamples.Dilutionshouldbemadeifasamplehasconcentrationsabovethehigheststandard.
Calculations
1.Soilmass—partspermillion
ReportsoilMehlich3extractablemacronutrientstothenearest0.1mgkg-1andmicronutrientstothenearest0.01mgkg-1:
Soilnutrientsmgkg-1=(mgL-1inextract-methodblank)×10
2.Soilvolume—partspermillion
ReportsoilMehlich3extractablemacronutrientstothenearest0.1mgdm-3andmicronutrientstothenearest0.01mgdm-3
Soilnutrientsmgkg-1=(mgdm-3inextract-methodblank)×10
3.Poundsperacrefurrowslice(AFS)
Nutrientsinlbs/acre,assumingAFSis15cm(or6inch)withsoildensityof1.35g/cc
Soilnutrientslb/acre=soilnutrientsmgkg-1×2
AnalyticalPerformance
1.ThemodernICPcanreliablydetectmacronutrientsto0.1ppmandmicronutrientsto0.01ppm,whicharesatisfactoryformakingfertilizerrecommendations.TherepeatabilityandreproducibilityofM3forplantavailablemacro-andmicro-nutrientswerethoroughlyevaluatedthroughinter-laboratorystudiesbyZhangetal.(2009)andSchroderetal.(2010).Overall,therepeatabilityandreproducibilityofM3werewithintheacceptablerange.
Interpretation
1.ThemethodoutlinedhereisconvenientinextractionandquantifyingplantavailablenutrientsinthesoilwithanICPinstrument.However,thecorrespondingfertilizerrecommendationsmustbebasedonfieldresponseevaluation(calibration)conductedunderlocalsoil-climate-cropconditions.
2.CautionsareneededwhenuseICPresultswithPrecommendationsdevelopedusingcolorimetricmethodsincetherecouldbedifferencesintheamountofPquantifiedespeciallyatthelowlevelwherefertilizersareneeded.ICPhasbeenreportedtogivehigherPvaluethanthatofcolorimetricmethodfromthesameextract(Pittmanetal.,2005).
EffectsofStorage
1.Air-driedsoilsmaybestoredseveralmonthswithoutaffectingtheM3Pmeasurement.
2.TheM3extractionsolutionisstableandcanbestoredforseveralweeksduetoitsacidicnature.Aspecificshelflifeisnotknown.
Safetyanddisposal
1.Thechemicalsusedinthisprocedureposenosafetyriskandthereforecanbestoredanddisposedofaccordingtoroutinelaboratoryprocedures.SomelabsmayrequireneutralizationbeforepouringextractedM3solutionintothesinkduetolowpH.
References
Mehlich,A.1978.Newextractantforsoiltestevaluationofphosphorus,potassium,magnesium,calcium,sodium,manganese,andzinc.Commun.SoilSci.PlantAnal.9(6):
477-492.
Mehlich,A.1984.Mehlich-3soiltestextractant:
amodificationofMehlich-2extractant.Commun.SoilSci.PlantAnal.15(12):
1409-1416.
Murphy,J.,andP.Riley.1962.Amodifiedsinglesolutionmethodfordeterminationofphosphatesinnaturalwaters.Anal.Chim.Acta27:
31-36.
Pittman,J.,H.Zhang,J.L.Schroder,andM.E.Payton.2005.Differencesofphosphorusinmehlich3extractsdeterminedbycolorimetricandspectroscopicmethods.Commun.SoilSci.andPl.Anal.36:
1641-1659.
Schroder,J.L.,H.Zhang,J.R.Richards,andM.E.Payton.2010.Aninter-laboratoryvalidationofMehlich3asauniversalextractantforplantnutrients.J.AOACInternational(accepted).
Rodriguez,J.B.,J.R.Self,andP.N.Soltanpour.1994.Optimalconditionsforphosphorusanalysisbytheascorbicacid-molybdenumbluemethod.SoilSci.Soc.Am.J.58:
866-870.
Zhang,H.,S.Kariuki,J.Schroder,M.Payton,andC.Focht.2009.Inter-laboratoryvalidationoftheMehlich3forextractionofplant-availablephosphorus.J.AOACInternationalVol.92
(1):
91-102.
主要作物养分含量表
注:
据多点多年土壤监测资料汇总得出,供计算作物吸收量时参考。
作物名称
果 实
茎 叶
N%
P%
K%
N%
P%
K%
水稻
1.212
0.300
0.370
0.773
0.130
1.804
玉米
1.465
0.317
0.528
0.748
0.412
1.266
小麦
2.160
0.370
0.425
0.565
0.067
1.280
棉花
3.920
0.628
0.921
1.167
0.245
1.731
油菜
3.966
0.679
1.236
0.782
0.149
1.506
大豆
6.272
0.636
1.713
1.289
0.173
1.287
花生
4.182
0.305
0.723
1.343
0.127
0.841
豌豆
4.377
0.410
1.100
1.400
0.153
0.415
大麦
2.016
0.287
0.838
0.479
0.103
1.099
高粱
1.326
0.385
0.397
0.436
0.170
1.206
谷子
1.456
0.267
0.592
0.595
0.068
1.718
荞麦
1.100
0.180
0.230
0.850
0.310
1.810
蚕豆
3.959
0.534
1.100
4.160
0.100
1.102
红豆
5.850
1.450
2.500
1.195
0.810
0.495
红薯
0.671
0.264
0.596
1.453
0.296
1.333
马铃薯
1.167
0.181
1.259
0.987
0.086
0.668
芝麻
3.028
0.668
0.502
0.386
0.107
2.107
烤烟
2.634
0.184
1.849
1.626
0.286
2.714
甘蔗
0.221
0.048
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