S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 227
Chemical solubility and agricultural performance of P-containing recycling fertilizers
SylviaKratz*,1SilviaHaneklaus*andEwaldSchnug*
*1 JuliusKühn-Institut,FederalResearchCentreforCultivatedPlants,InstituteforCropandSoilScience,Bundesallee50,38116Braunschweig,Germanycorrespondingauthor:[email protected]
Abstract
158P-containingfertilizers,standardmineralandrecyc-lingproducts,wereanalyzedfor theirchemicalsolubilityusing10differentmethods.Correlationsbetweenmethodswerehighlysignificant,indicatingthatareductionofof-ficialmethodsisviable.AmodifiedNeubauerpottrialwascarriedoutwithdifferentP-recyclingproductsto investi-gatewhichmethodwasbestsuitedtodescribetheirplantavailability.Thebestcorrelationbetweenshort-termplantPuptakeandchemicalsolubilitywasfoundforwaterex-traction,whilemidtolong-termPavailabilityisbetterde-scribedbyextractionswithammoniumcitrate.ForreasonsofpracticabilityitisrecommendedtousetheEUmethodof neutral ammonium citrate extraction to evaluate thenutritivevalueofP-recycling fertilizers.The tradable (so-calledtotal)PcontentofafertilizercanbedescribedbytheEUmineralacidextractionwithH2SO4+HNO3oraqua regiadigestion.
Keywords: Recycling fertilizers, P solubility, chemical ex-traction methods, P plant availability, Neubauer pot trial
Zusammenfassung
Löslichkeit und agronomische Qualität von P-hal-tigen Recyclingdüngern
158 phosphorhaltige Düngemittel, darunter Standard-mineraldünger und Recyclingprodukte, wurden mit 10verschiedenenMethoden auf ihre chemische Löslichkeituntersucht.HochsignifikanteKorrelationenzwischendenMethoden legtennahe,dassesmöglich ist,dieVielzahlderoffiziellenMethodenzurBeschreibungderP-Löslich-keitzureduzieren.MithilfeeinesmodifiziertenNeubauer-KeimpflanzenversucheswurdeunterEinsatzverschiedenerP-Recyclingprodukte untersucht, welche Methode ambesten zur Beschreibung der Pflanzenverfügbarkeit die-serProduktegeeignetist.DiebesteKorrelationzwischenkurzfristiger Pflanzenaufnahme und chemischer Löslich-keitwurde fürdieWasserextraktiongefunden,währendsichdiemittel-bislangfristigeP-Verfügbarkeitbessermit-tels Extraktionen mit Ammoniumcitrat beschreiben ließ.AusPraktikabilitätsgründenistdieEU-MethodezurExtrak-tion mit neutralem Ammoniumcitrat zu empfehlen, umdasDüngepotentialvonP-Recyclingdüngernzubewerten.Der marktfähige (“so genannte totale”) P-Gehalt einesDüngers kann mittels Mineralsäureextraktion nach EU-Vorschrift (H2SO4 + HNO3) oder Königswasseraufschlussbeschriebenwerden.
Schlüsselwörter: Recyclingdünger, P-Löslichkeit, chemische Extraktionsmethoden, P-Pflanzenverfügbarkeit, Neubauer-Keimpflanzenversuch
228
1 Introduction
The German Fertilization Ordinance (Düngeverord-nung–DüV)holds anobligation for farmers to fertilizetheir crops according to Good Agricultural Practice, i.e.accordingtocropnutrientdemands.In§5DüV,thebal-ancesurplusforphosphateislimitedto20kgP2O5/ha*yr.PrerequisiteforthisisanefficientPfertilizationwithmini-mizedPlosses.Inordertorealizethis,apreciseestimateof theplant available (“efficient”) shareof fertilizer P isneeded.Theextractionwithchemicalsolventsgivesafirstorientationabouttheefficiencyoffertilizers.TheGermanFertilizerOrdinance(Düngemittelverordnung–DüMV,An-nex2, Table4)offers11options todescribephosphatesolubility, most of them identical to themethods givenby theEU regulation2003/2003on fertilizers.The largenumberofdifferentmethodshashistoricalroots.Itisim-perativethatmethodsarecomparableinordertocalculatereliablefertilizerrates.Forthisreason,theGermanFederalMinistryforNutrition,AgricultureandConsumerProtec-tion(BMELV)initiatedaresearchprojectonthe“Standard-izationofphosphateanalysisandcharacterizationoffertil-izers”,whichwascarriedoutbytheJuliusKühn-Instituteintheyears2008and2009.Theprojecthadthreemainaims:
• to reduce the multitude of chemical extraction me-thodsforcharacterizingphosphatesolubility,
• tofindaclearandsimpledefinitionofmethodswithregardtotheirexplanatorycontentaboutthesolubilityofthefertilizer,i.e.
- Water:immediatelyavailable(initialeffect) -Weak acid: available within the first vegetation period
- Strongacid(mineralacid):maximumamountofP whichmaypotentiallybecomeavailable/tradable totalcontent,
• toexaminethecorrelationbetweenchemicallyextrac-tablePcontentandagronomicalefficiencyusingare-presentativeselectionofPcontainingfertilizerswhicharecurrentlymarketedincludingorganicfertilizers(far-myardmanure,sewagesludge,compost,animalresi-dues)and„new“products(suchasfertilizersbasedonsewagesludgeash).
2 Material and methods
2.1 Laboratory screening of fertilizers
P-containingfertilizersweremainlysuppliedbybranchesofthegovernmentalfertilizercontrol(Düngemittelverkehrs-kontrolle). Further samples of „new“ products such asthose fromwastewater treatmentoranimalwastepro-
ductswereprovidedbyBerlinerWasserbetriebe(BWB),awastewatertreatmentplantinGifhorn,theFederalInsti-tuteforMaterialsResearchandTesting(BAM)Berlin,Ash-DecUmweltAG,ReFoodGmbHandtheAssociationforTechnologyandStructuresinAgriculture(KTBL)DarmstadtaswellasfromthecollectionsofJKI.Table1givesanover-viewofthesamplesanalyzedinthisproject.
Table1:
Overviewoftheanalyzedfertilizersamples(N=158)
Group Type descriptionNo. of
samples
Mineral fertilizers 77
StraightPfertilizersSingle(SSP)andTripleSuper-phosphate(TSP)
2+6
(Soft)groundrockphosphate 4
Partiallyacidulatedrockphosphate
7
Compoundfertilizers NPKfertilizer 30
NPfertilizer 15
PKfertilizer 11
LimewithP 2
Organic and organo-mineral fertilizers and products based on them
81
Sewagesludge OrganicNPfertilizer 11
OrganicPandNP(MAP)fromwastewaterprecipitation
1+1
Sewagesludgeash 6
P,PKandNPKfromthermo-chemicallytreatedsewagesludgeash
22+5+2
Biowastecompost OrganicNPK/PKfertilizer 5
Fermentationresidues OrganicNPKfertilizer 4
Slurry(cattleandpig) OrganicNPKfertilizer 16
Meatandbonemeal(+ash)OrganicNP(+mineralP)fertilizer
6+1
Vegetableresidues(vinasse/melasse)
OrganicNPKfertilizer 1
Total: 158
Samplepreparation:Inthecaseofmineralfertilizersandmineralproductsfromsewagesludgeash/meatandbonemealash,theoriginalsubstance,conditionedat40°Candfine-groundtoaparticlesizeof<60µminaRetschRS1vibratingdiscmillwithzirconiumoxidegrindingequip-ment,wasusedforallextractionsanddigests.Fermenta-tionresiduesandslurriesdeliveredas liquidsamples (ex-ceptforonesolidsample)weredriedinaventilatedovenat60°Candfine-groundtoaparticlesizeof<60µminatungstencarbidemortarorvibratorydiscmillwithzirco-niumoxidegarniturebeforeextraction.
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 229
Thefollowingmethodswereusedtodescribethesolu-bilityofthefertilizersamples(Table2).Fortheslurries,onlyaselectionof theabove listedmethodswasapplied (W,CAL,CA,AR).
Table2:
ChemicalextractionmethodsusedforthedescriptionofPsolubility
Code Method
MinALUFA MineralaciddigestaccordingtoVDLUFAII4.1.1.2(HNO3+H2SO4+CuSO4)
MinAEU MineralaciddigestaccordingtoEU-method3.1.1(HNO3+H2SO4)
AR Aqua regiadigestaccordingtoDINEN13346/2001-04
FA Extractionwith2%formicacid(VDLUFAII4.1.2)
CA Extractionwith2%citricacid(VDLUFAII4.1.3)
NACEU ExtractionwithneutralammoniumcitrateaccordingtoEU-method3.1.4
W+NACFN ExtractionwithwaterandneutralACaccordingtoFresenius-Neubauer(VDLUFAII4.1.4)
AAC ExtractionwithalkalineammoniumcitrateaccordingtoPetermannat20°C(VDLUFAII4.1.5)
W Extractionwithwater(VDLUFAII4.1.7)
CAL ExtractionwithcalciumacetatelactateaccordingtoSchül-ler(1969)/BGKeVbookofmethods
P determination was done colorimetrically (Molyb-denum-Blue) according to Murphy & Riley (1962) with(NH4)6Mo7O24x4H2O.TheLUFA-andtheEU-methodformineralaciddigestion
yieldedcomparableresults(R2=0.999,p<0.01),there-foretheEU-methodwasusedexclusivelyforthecompletesampleset.Highlycorrelatingresultswerealsoobtainedfor AR andMinAEU digestion (P-AR (mg/kg) = 0.986*P-MinA(mg/kg)+1595(withp<0.0005;R2=0.993)).ThusexistingdataforARdigestionofsewageslusdgeashprod-uctscouldbeusedforcalculatingtheMinAEUcontent.
2.2 Modified Neubauer trial
TheaimoftheNeubauertrialwastoexaminethecor-relationbetweenchemicalPsolubilityofPrecyclingfertil-izersandPuptakeandeffectsonyield,respectively.Thequestion tobeansweredwaswhichchemicalextractionmethodisbestsuitedtoassessthebioavailabilityofPinrecycling fertilizers. To answer this question, amodifiedshort-termNeubauer trialwassetup:PrincipleoftheNeubauermethodistouseplantroots
as “reagents” to determine the amount of “root solu-ble” and thus plant available nutrients.A largenumberofplants(100ryeseeds)onasmallamountof(fertilized)substratemakessurethatrootsolublenutrientsareusedupwithin a short periodof time (14 to18days), given
thatabioticfactorsareoptimum(NeubauerandSchneider,1923;Neubauer,1931).450 g of fertilized substratewere filled into transpar-
entpolystyrolvessels(diameter12cm,height6cm)andseededwith100ryeseeds.Theexperimentwasdesignedasan“exhaustiontrial”,meaningthatafterafirstcutofshootsafter16days(atBBCH12/13)(Straußetal.,1994)plantswerefurthercultivateduntilvisiblesymptomsofnu-trientdeficiencywereobserved,accompaniedbyretardedgrowth.Asecondandathirdcutwerecarriedoutafter29(BBCH12)and43days(BBCH11/12),togetherwitharecoveryofroots.Astestplant,thesummerryecultivarArantes (thousand
grainweight:41.3g,germinability:89%),wasusedun-dressed.ThetestsubstratewasP-freequartzsand[grad-ing:“fine“sand:0.1to0.4mm,coarsesand0.7to1.2mm].Quartzsandwasfilledintothevesselsinthreelayers:Thebottomlayerconsistedof50gcoarseand100gfinesand,whichwasmixedwith the ground test fertilizers.Thislayerwasalsosprinkledwiththesupplementalfertiliz-ersolutions.Ontopofthis,alayerof150gfinesandwasplaced.Ryeseedswereevenlyspreadontopofthesecondlayerandcoveredwithathirdlayerof150gfinesand.SeedingdatewasMay20,2009.Thefirstcutwashar-
vested16dayslateratBBCH12/13(Straußetal.,1994)onJune5,2009.Thesecondcutwasperformed29daysaftersowingatBBCH12onJune18,2009andthethirdcutafter43daysatBBCH11/12onJuly2,2009.Allpotswerebrought toapproximately65%offield
capacitywithde-ionizedwater.Duringthetrial,waterwassuppliedindividuallyaccordingtopotweight.
Fertilizationstrategy:• Definedamountsof P coming fromdifferent P recy-cling fertilizers seeTable3+4 (calculationbasedontotalPsolubleinMinAEU)
• Plevels(severePdeficiency–optimum–Psurplus):20–40–60mgP(determinationofoptimumratewascalculatedbasedonPuptakeofshootdrymatterinapilottrialatanassumedPutilizationof20%)
• Supplementationof liquidN forall treatmentsup totheNamountsuppliedbyanN-containingtestfertili-zer(withoutconsiderationoffertilizerno.7)(Table5).Additionally,Nwasappliedatarateof10and5mg/potN,respectively,aftereachcut.
• UniformsupplementationofK,Ca,MgandSinliquidform(calculationbasedondrymatteryield fromthepilotexperimentandaveragenutrientcontent,consi-deringnutrientinputbytestfertilizers)(Table5)
• No micronutrients (as indicated by the pilot experi-ment)
• Controltreatmentswithseveralstandardmineralfer-tilizers(singlesuperphosphate,fullysolubleNP,partly
230
digestedrockphosphate),analyticalgrademonocalci-umphosphate(MCP)andazeroPtreatment,suppliedwithallothermacronutrientsinliquidformlikethetestfertilizers
Table3:
TestfertilizersusedintheNeubauertrial
Tr.1 Sample name
Description
ZeroP
1 OrgNPBM OrgNPfrombonemeal(Beckhornbonemealsteamed)
2 OrgNPMBM OrgNPfrommeatandbonemealcat.3(AntonKnollcompany)
3 MBMA Ashfrommeatandbonemealcat.1(Rethmann/ReFood)
4 OrgNPSS OrgNPfromsewagesludge(precipitation,WWTPGifhorn)
5 Struvite MAP(struvite)fromwastewaterprecipitation(BerlinerWasserbetriebe)
6 P-SSATC StraightPfromthermochemicallytreatedsewagesludgeash(MgCl2-type,BAM)
7 NPK-SSATC NPKfromthermochemicallytreatedsewagesludgeash(MgCl2-type,AshDec)
Controls:
8 MCP Monocalciumphosphateanalyticalgrade(p.a.)
9 SSP Singlesuperphosphate
10 DAP Diammoniumphosphate
11 paRP Partlyacidulatedrockphosphate
1Tr.=treatment
Table5:
Fertilizersolutionsandnutrientdosageappliedperpot intheNeu-bauertrial
Nutrient Compound used Dosage (mg pure nutrient per pot)
N NH4NO3,KNO3,Ca(NO3)2 89.5
K KNO3,K2SO4 60.0
Ca Ca(NO3)2 20.0
Mg MgSO4 4.0
S MgSO4,K2SO4 5.3
ForthedeterminationofP,theplantmaterialwasdriedinaventilatedovenat60°Cuntil constancyofweight.Then thematerial was fine-ground to a particle size of< 0.12 mm employing an ultra-centrifugal mill (RetschZM1)withtitaniumgrindingequipment.0.5gplantmate-rialwasdigestedwith4mlHNO3+1mlH2O2inamicro-wave(CEM/Mars)at600Wattfor27minutes,raisingthetemperatureupto200°C.Aftercoolingdownthedigestwasfilledupto50mlwithdeionizedwater.Pconcentra-tionwasdeterminedbyICP-OES(SpectroM120S).
3 Results and discussion
3.1 Laboratory investigations
Figure 1 showsmedian, quartiles and ranges of P2O5contents of the different fertilizer types determined inmineralacid(MinAEU)andaqua regia(AR).Pcontentsintheseextractantsaregenerally termed“so-called total”,
Table4:
Pcontentandrelativesolubility(in%ofMinA-P2O5)ofthefertilizersusedintheNeubauertrial
Tr. Type MinA-P2O5 (%) Relative solubility (in % of MinA-P2O5) in ...
FA CA NACEU W+NACFN AAC W
1 OrgNPBM 15.0 76 34 27 33 8.5 0.93
2 OrgNPMBM 17.4 91 74 48 65 16.0 0.99
3 MBMA 25.9 48 50 15 15 7.0 0.01
4 OrgNPSS 8.9 57 84 88 86 80.0 0.40
5 Struvite 27.6 97 100 92 51 6.3 0.73
6 P-SSATC 21.4 75 65 21 21 4.8 0.13
7 NPK-SSATC 7.4 101 103 92 92 70.0 73.00
8 MCP 57.4 97 98 97 98 95.0 96.00
9 SSP 20.9 101 88 84 87 83.0 76.00
10 DAP 45.8 115 101 102 103 107.0 87.00
11 paRP 41.6 76 69 65 71 66.0 53.00
FA-formicacid;CA–citricacid;NACEU-neutralammoniumcitrate;W+NACFN-waterandneutralAC;AAC-alkalineammoniumcitrate;W–water(Tr.=treatment)
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 231
Figure1:
Mineralacid(MinA)andaqua regia(AR)solubleP2O5contentsoftheanalyzedfertilizers(%oforiginalsubstance)–median,quartilesandranges
(1=organicfertilizers,2=solublemineralfertilizers,3=rockphosphates(RP),4=Pfertilizerswithlime,5=productsfromsewagesludgeash(SSA),6=productsfromwastewater(WW)treatment,7=meatandbonemealash)=outlier,*=extremevalue,numbersrefertoBMELV-samplenumberandthusareonlydescriptive
60
50
40
30
20
10
0
Fertilizer type
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
124
60
50
40
30
20
10
0
Fertilizer type
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
7015
12
3
1***P
O_
Min
A(%
)2
5
PO
_A
R(%
)2
5
becauseonlynon-destructivemethodssuchasXRFdeter-mine the real total content (Haneklausetal.,1994).Ex-pectedly(seeabove)bothmethodsyieldedsimilarresults.Similarly, therewas a strong relationship between the
GermanandEU-method forextractionwithneutralam-moniumcitrate(Table6).
Table6:
PearsoncorrelationcoefficientsfortherelationshipbetweenGermanandEU-methodforthedeterminationofPsolubilityinneutralammo-niumcitrate(W+NACFNandNACEU)
Group of samples n r p
Allsamples 143 0.993 0.01
Mineralfertilizersonly 75 0.999 0.01
Organicfertilizersonly 27 0.983 0.01
Sewagesludgeash(products)only 35 0.676 0.01
While there was a very strong and highly significantcorrelationbetweentheGermanandtheEU-methodformineralaswellas fororganic fertilizers, itwasdistinctlyweakerforsewagesludgeashesandtheirproducts.Ascanbeseenfromthecorrelationmatrices(Table7to
10),therewerecloserelationshipsbetweenallexaminedextractionmethodswhenallfertilizerswereviewedasonegroup. However, when the different types of fertilizersweregroupedseparately,therewereobviousdifferences:Whilecommonmineralfertilizersshowedverystrongandhighlysignificant(p<0.01)correlationsinallcases,sew-
agesludgeashesandtheirproductsshowedaheteroge-neous picture,with only occasionally significant correla-tionsbetweendifferentextracts.Itisspeculatedthatthismightbeduetotheheterogeneityintheproducts.Incon-trasttotheashproducts,thegroupoforganicfertilizersshowedformostextractions–exceptwater–mediumtovery strong, significant to highly significant correlations.Thereasonfortheunpredictableresultsforthewaterex-tractionisprobablythefactthatthedriedorganicsampleshadhydrophobicsurfacesandwerethereforedifficulttomoisteninwater.Figure2givesanoverviewofrelativePsolubilitiesoffer-
tilizertypesindifferentextractants.Sincethelargegroupofash-basedfertilizerswasnotdigestedinmineralacid,relativesolubilitiesarereferredtoaqua regiahere.Relativesolubilityinthegroupoforganicfertilizers(1-org)showedahighvariability.Acomparablebehaviorwasalsofoundinotherextractstestedinthisstudy(figuresnotshownhere).Thiswasnotonlybecause thisgroupwas composedofdifferentsubtypes(farmyardmanure,biowastecompost,sewagesludge,meatandbonemeal, fermentation resi-duesandvegetableresidues)butalsoduetotheinternalheterogeneityofeachofthesesubgroups,whichdidnotallowapreciseevaluationoftheirquality.The products from sewage sludge ash also showed a
highlyvariablesolubility(type5:SSA,SSA-P,SSA-PK,SSA-NPK), inparticular thegroupofP fertilizers fromunpro-cessed thermochemically treated ash. This group com-prised22samples(SSA-P).Obviously,thismaterialwasstill
232
Table7:
Pearsoncorrelationcoefficientsfortherelationshipbetweendifferentextractionmethods,calculatedforallfertilizers(seeTable1)
MinAEU AR FA CA W+NACFN NACEU AAC W
MinAEU 1
AR 0.992** 1
FA 0.967** 0.942** 1
CA 0.958** 0.942** 0.981** 1
W+NACFN 0.944** 0.877** 0.961** 0.956** 1
NACEU 0.941** 0.890** 0.960** 0.962** 0.993** 1
AAC 0.902** 0.838** 0.911** 0.918** 0.969** 0.966** 1
W 0.889** 0.827** 0.923** 0.923** 0.964** 0.959** 0.966** 1
CAL 0.920** 0.926** 0.961** 0.966** 0.974** 0.976** 0.957** 0.973**
MinALUFA-Mineralaciddigest;MinAEU-Mineralaciddigest;AR-Aqua regia;FA-2%formicacid;CA-2%citricacid;NACEU-neutralammoniumcitrate;W+NACFN-waterandneutralAC;
AAC-alkalineammoniumcitrate;W-water;CAL-calciumacetatelactate;Significances:**=p<0.01,*=p<0.05,n.s.=notsignificant
Table8:
Pearsoncorrelationcoefficientsfortherelationshipbetweendifferentextractionmethods,calculatedformineralfertilizers(seeTable1)
MinAEU AR FA CA W+NACFN NACEU AAC W
MinAEU 1
AR 0.997** 1
FA 0.974** 0.978** 1
CA 0.959** 0.962** 0.987** 1
W+NACFN 0.954** 0.958** 0.984** 0.994** 1
NACEU 0.948** 0.953** 0.983** 0.994** 0.999** 1
AAC 0.922** 0.924** 0.948** 0.967** 0.970** 0.972** 1
W 0.924** 0.926** 0.957** 0.977** 0.979** 0.981** 0.968** 1
CAL 0.912** 0.918** 0.949** 0.958** 0.969** 0.971** 0.947** 0.967**
MinALUFA-Mineralaciddigest;MinAEU-Mineralaciddigest;AR-Aqua regia;FA-2%formicacid;CA-2%citricacid;NACEU-neutralammoniumcitrate;W+NACFN-waterandneutralAC;
AAC-alkalineammoniumcitrate;W-water;CAL-calciumacetatelactate;Significances:**=p<0.01,*=p<0.05,
n.s.=notsignificant
Table9:
Pearsoncorrelationcoefficientsfortherelationshipbetweendifferentextractionmethods,calculatedforproductsfromsewagesludgeash(seeTable1)
MinAEU AR FA CA W+NACFN NACEU AAC W
MinAEU 1
AR n.c. 1
FA n.c. n.s. 1
CA n.c. 0.341* 0.820** 1
W+NACFN n.c. n.s. 0.550** 0.467** 1
NACEU n.c. 0.378* n.s. n.s. 0.676** 1
AAC n.c. n.s. -0.472** -0.414* n.s. 0.515** 1
W n.c. -0.503** n.s. n.s. n.s. n.s. 0.416* 1
CAL n.c. n.c. n.c. n.c. n.c. n.c. n.c. n.c.
MinALUFA-Mineralaciddigest;MinAEU-Mineralaciddigest;AR-Aqua regia;FA-2%formicacid;CA-2%citricacid;NACEU-neutralammoniumcitrate;W+NACFN-waterandneutralAC;
AAC-alkalineammoniumcitrate;W-water;CAL-calciumacetatelactate;Significances:**=p<0.01,*=p<0.05,
n.s.=notsignificant,n.c.=notcalculated
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 233
Figure2:
Relativesolubility(referredtoaqua regia(AR))ofdifferentfertilizertypesinwater(W),neutralammoniumcitrate(NACEU),citricacid(CA)andformicacid(FA)–median,quartilesandranges
(1=organicfertilizers,2=solublemineralfertilizers,3=rockphosphates(RP),4=Pfertilizerswithlime,5=productsfromsewagesludgeash(SSA),6=productsfromwastewater(WW)treatment,7=meatandbonemealash)=outlier,*=extremevalue,numbersrefertoBMELV-samplenumber
120
100
80
60
40
20
0
Fertilizer type
CA
(%A
R)
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
120
100
80
60
40
20
0
Fertilizer type
NA
C(%
AR
)E
U
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
Fertilizer type
120
100
80
60
40
20
0
W(%
AR
)
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
2
104
3198
1926
2427
39
98
5999
70
61
17
28
99
19
13117
170
22
19
17
33
3359
27
26
19
* *
**
*
140
120
100
80
60
40
20
0
Fertilizer type
FA
(%A
R)
1-org2-m
inPK
5-SSA-P
6-WW
-P
2-minN
P
3-paRP
5-SSA
7-MBM
A
2-minN
PK
3-RP
5-SSA-N
PK
2-minP
4-P-lim
e
6-WW
-NP
103
23
23
33
61
rather heterogeneous in its speciationdespite the treat-mentandmilling.Thestandardmineralfertilizers(types2,3and4)stood
outwiththeir inmostcasescomparably lowvariationindifferentextractants.Formineralfertilizersandsewagesludgeashproducts,
thewaterextractdidnotfollowthetrenddescribedhere:While the ash products showedmostly a uniformly low
watersolubility,thestandardmineralfertilizersdisplayedvaryingwater solubilitydependingon theirdifferentde-greeofacidulation.Duetotheobservedvariation insolubilitybothwithin
andbetweengroupsitwasnotpossibletoderivereliablestatisticalparameterssuchasconfidenceintervalsormeansolubility factorsfromthissampleset.Thiswill requirealargersetofsamples.
234
Table10:
Pearsoncorrelationcoefficientsfortherelationshipbetweendifferentextractionmethods,calculatedfororganicfertilizers(seeTable1)
MinAEU AR FA CA W+NACFN NACEU AAC W
MinAEU 1
AR 0.984** 1
FA 0.951** 0.952** 1
CA 0.933** 0.900** 0.834** 1
W+NACFN 0.945** 0.899** 0.844** 0.977** 1
NACEU 0.897** 0.825** 0.744** 0.958** 0.983** 1
AAC 0.755** 0.631** 0.505* 0.875** 0.866** 0.934** 1
W n.s. n.s. n.s. n.s. n.s. n.s. n.s. 1
CAL 0.777** 0.584** 0.878** 0.821** 0.741** 0.692** n.s. 0.902**
MinALUFA-Mineralaciddigest;MinAEU-Mineralaciddigest;AR-Aqua regia;FA-2%formicacid;CA-2%citricacid;NACEU-neutralammoniumcitrate;W+NACFN-waterandneutralAC;
AAC-alkalineammoniumcitrate;W-water;CAL-calciumacetatelactate;Significances:**=p<0.01,*=p<0.05,
n.s.=notsignificant
3.2 Modified Neubauer trial
3.2.1 Dry matter yield
Thetotalyieldofallthreecutsincludingrootsdifferedsignificantlybetweenzerocontrolandallothertreatments(Table11).Ingeneral,differencesbetweenPformsprovedtobenotsignificant.Acleardifferentiationbetweencon-ventionalandrecyclingfertilizerswasnotpossible.Treat-ment7(NPK-SSATC)displayedloweryieldsatcut2and3,whichmightbeduetotheexcessiveNsupplyforcedbytheparticularcompositionofthisfertilizer(unsuitableN:P-ratio)1.Inaddition,supplementationofpotassiumbyuseofKClmighthaveweakenedtheplantsinthistreatment,since therewas no buffering in the sand substrate (salteffect). Surprisingly, treatment 8 (MCP) produced loweryieldsthanallothertreatmentsalthoughitsPcontentwascompletely water-soluble. Treatment 10 (diammoniumphosphate)showedsignificantlyhigheryieldsthansomeoftheothertreatments.
1 Treatment7wasamultinutrient(NPK)fertilizerbasedonsewagesludgeash.InordertotestthequalityofthePcomponent,itwasdecidedtosupplyPsolelyfromthatfertilizerdespitethefactthatthismeantanexcessiveNsup-plyatthesametime(Plevel20:126mgN,Plevel60:378mgNperpot).Whileplantswereabletotoleratethisuptothefirstcut,therewasaclearyielddepressionatPlevels40and60atcut2,followedbyatotalcollapseoftheplantsbeforecut3.
Table11:
Meandrymatter yields (gDM/pot) of the different fertilizer treat-mentsintheNeubauertrial,cuts1to3(shoots)+roots(drymatteryieldzeroP:1.78g/pot)(Tr.=treatment)
P level 20 P level 40 P level 60
Tr. DM (g/pot) Tr. DM (g/pot) Tr. DM (g/pot)
6 3.53a 7 2.80a 7 3.01a
11 3.61ab 8 2.83a 6 3.30ab
3 3.74abc 9 2.93ab 8 3.68ab
5 3.82abc 4 3.73bc 9 3.72b
9 3.98abc 11 3.74bc 11 3.81b
2 3.99abc 6 3.87c 4 3.82b
4 4.00abc 1 3.91c 5 3.82b
7 4.06abc 5 3.95c 10 3.88b
8 4.11abc 10 4.00c 2 3.89b
1 4.25bc 2 4.11c 3 3.90b
10 4.42c 3 4.11c 1 3.93b
differentlettersindicatesignificantdifferencesbetweentreatments(Tukey,p<0.05)
3.2.2 P content of plants
IncreasingPlevelsfrom20to60mgperpotweredis-playedinanincreasingPcontentofshoots(Table12).Thiseffectwasnotclearintreatment3:cuts1to3,treatment4:cut3,treatment6:cut1andtreatment9:cut2.In the treatments suppliedwith recycling fertilizers (tr.
1to7),Pcontentsofshootsincreasedconsistentlyfromcut1tocut3.Incomparisontothisfinding,thePcontentin the treatments fertilizedwith standardmineral fertil-izers (fully water-soluble products aswell as rock phos-phatebasedproducts, tr.8 to11) remainedconstantordecreased.
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 235
Table12:
MeanPcontentofshoots inthedifferentPfertilizertreatmentsoftheNeubauertrial
P level 20 P level 40 P level 60
Tr. P (mg/kg) Tr. P (mg/kg) Tr. P (mg/kg)
Cut1(ContentofzeroPtreatment:4019mg/kgP)
1 3182a 1 3181a 1 3072a
5 3253a 3 3603a 3 3650ab
2 3523ab 2 3853a 2 3856ab
3 3570ab 5 3859a 5 4194bc
4 4079bc 4 4654b 6 5010cd
6 4649c 6 4983b 4 5248d
7 6025d 9 7916c 11 9040e
8 6101d 7 8090c 9 9432e
11 6201d 11 8457cd 7 10562fg
9 6466d 8 8527cd 10 10649g
10 6475d 10 9319e 8 11061g
Cut2(ContentofzeroPtreatment:5229mg/kgP)
1 3682a 1 4102a 3 4216a
3 4340ab 3 4190ab 1 4410a
2 4512bc 2 5256bc 6 5750b
7 4591bcd 6 5515cd 2 6043b
4 4658bcd 4 5712cd 4 6083b
10 4720bcde 5 6240cde 5 6753bc
5 4921bcde 7 6632def 9 7881d
9 5038bcde 11 6956efg 11 7887d
6 5146cde 10 7227efg 7 8254de
8 5301de 9 7678fg 8 9105e
11 5455e 8 7871g 10 9359e
Cut3(nomorebiomassproductionfromzeroPtreatment)
1 4226 3 4408 3 4450
3 4666 1 4590 1 4691
7 4729 6 5732 6 5913
2 4858 2 6498 4 6493
10 5032 11 6617 2 7430
9 5086 4 6619 9 7442
6 5134 10 6948 11 7779
4 5291 9 7027 5 8755
8 5408 8 7294 8 8793
11 5489 5 7578 10 9311
5 6557
differentlettersindicatesignificantdifferencesbetweentreatments(Tukey,p<0.05)
(forcut3,noanalysisofvariancewaspossible,becauseduetoscarceplantbiomass
repetitionswerejoinedintoamixedsampleforchemicalanalysis)
Drymatter yieldsof all 11 treatmentsdecreased fromcut1tocut3(Table11).Thus,theobserveddifferencesinPcontentbetweenrecyclingandmineralfertilizerscannotbeexplainedbyadilutioneffectduetoincreasingbiomass
production.Rather,adifferentqualityorPavailabilityofthefertilizercanbeassumedasthemainreason.Thestan-dardmineralfertilizerswereinstantlyavailableandthere-foretakenuptoalargerextentbeforethefirstcut,whilePinrecyclingfertilizerswasmoreslowlyavailable,yetre-leasedandtakenupcontinuouslybytheplantsthrough-outtheentireexperimentof43days.
3.2.3 Plant P uptake
Tables13to15giveanoverviewofthenetplantPup-take (roots, shoots and total produced biomass). Net PuptakewascalculatedbysubtractingthePuptakeofthezeroP treatment (representingP reserves in seeds) fromthatofthefertilizedtreatments.ThePutilizationratewascalculatedforcut1andtotalyield(includingroots).PlantssuppliedwithmineralPfertilizersclearlyshowa
highertotalPuptakethanthosewhichreceivedrecyclingfertilizers (Table13).Graded ratesof standardmineralPfertilizerswere reflected in increasingPuptake. In com-parison,Pwastakenupatlowratesfromrecyclingfertil-izersandresponsestothedoseweremarginalatbest.ThisindicatesthelimitedPpotentialoftherecyclingfertilizers.In thegroupofmineral fertilizers,diammoniumphos-
phate(tr.10)showedthehighestPuptake,while inthegroupof recycling fertilizers, struvite (tr.5)was theonewith the highest P uptake. However, the difference be-tween treatment 5 and treatments 4 (org NPSS), 2 (orgNPMBM) and6 (P-SSATC)proved tobenot significant (seeTable13).Bonemeal(tr.1)andmeatandbonemealash(tr.3)displayedthelowestPuptakeofalltestedproducts.OneexceptiontothegeneraldifferencebetweenmineralandrecyclingfertilizerswasNPK-SSATC(tr.7),ahighlysol-ubleproduct,whichcontainedTSPtoadjustitsPcontent.ThisproductyieldedasimilarPeffectasstandardmineralPfertilizersatthefirstcut.ItsunsuitableN:Pratio,however,increasinglyimpaireditsperformancewithgradedPlevels(seefootnote1).Withreferencetothetotalproducedbiomass(rootsand
shoots), utilization rates were extraordinarily high withup to 92%of the P supply. This ismore than 4 timeshigher than theaverage valueof20%given in the lit-erature(Finck,1992).Thisdifferencecanbeexplainedbytheparticular set-upof theNeubauer testwith its largenumberofseedsonasmallamountofsubstrate,whichisexplicitlydesignedtoachievecompleteutilizationofPoranestimateofthetotalpotentiallyavailableP.Theresultsofthisexperimentsuggestthatthepotentialofthetestedfertilizers should preferably be evaluated and comparedbasedontheresultsforPlevel20ashighutilizationrateswerealreadyrealizedatthatlevel.Lookingindividuallyatthedifferentcuts(Table14),the
first harvest reflected differences between treatments in
236
Table13:
MeannetPuptakeandutilizationrate(UR,in%ofPsupply)oftotaldrymatteryield(cut1to3includingroots)inthedifferentPfertilizertreat-ments(Tr.=treatment)
P level 20 P level 40 P level 60
Tr. P uptake (mg) UR (%) Tr. P uptake (mg) UR (%) Tr. P uptake (mg) UR (%)
1 07.9a 40
3 08.1a 40 1 08.0a 20 1 08.3a 14
2 09.4a 47 3 09.4ab 23 3 09.1ab 15
6 09.5ab 47 6 11.5ab 29 6 10.9abc 18
5 10.0ab 50 4 11.8ab 30 2 12.5abc 21
4 10.3ab 51 2 12.1b 30 4 13.9bc 23
11 13.0bc 65 5 12.7b 32 5 15.1c 25
7 14.9cd 74 9 17.8c 44 11 24.0d 40
9 15.7cd 78 8 18.4c 46 9 24.7d 41
8 16.0cd 80 11 21.5cd 54 8 25.5d 42
10 18.3d 92 10 24.2d 61 10 29.3d 49
differentlettersindicatesignificantdifferencesbetweentreatments(Tukey,p<0.05)
thesamewayasthesumofallcuts.Thismirrorsthead-vantageofthewater-solublePfertilizersduringtheinitialgrowthstage.Incut1,theplantsfertilizedwithNPK-SSATC(tr.7)werestillperformingextraordinarilywell.Thiswasthe only recycling fertilizer reaching the same level of Puptake as themineral fertilizers. Following treatment 7,thesecondhighestPuptakeofrecyclingfertilizerswasob-servedforP-SSATC(tr.6)andorgNPSS(tr.4),respectively.Bonemeal(tr.1)displayedthelowestPuptake.With15to52%atPlevel20and5to23%ofPsupplyatPlevel60,Putilizationratesatcut1wereratherhigh.Atthesecondharvest(cut2,after29days)differences
between standard mineral and recycling fertilizers wereconsiderably smaller. The reasonmightbe thatby then,thenon-water solubleportionof the recycling fertilizershadbecomeavailable.Apparently,theinitialadvantageofthewater-solublePwasover timecompensatedat leastpartiallybynonwater-solubleP forms (particularly thosesolubleinneutralammoniumcitrate).However,Puptakeintherecyclingfertilizertreatmentswasstillbelowthatinthestandardmineral fertilizerstreatments, thoughthesedifferenceswerenotsignificantinallcases(Table14).Thistime,therecyclingfertilizerwiththehighestPuptakewasstruvite(tr.5),followedbymeatandbonemeal(tr.2).Intreatment7 (NPK-SSATC), P uptake at P level 40 and60was clearly reduced due to the yield depression,which,asdiscussedabove,hadbeencausedpresumablybytheunsuitableN:PratioresultinginanexcessiveNsupply.
Atthethirdharvest,thedifferenceinPuptake2betweenstandardmineralandrecyclingfertilizerswasinmostcasesnolongersignificant,ornotobservedatall.Obviously,theinitialadvantageofthemineralfertilizersbytheirwater-solublePwasalmostleveledoutbytheslowlyavailablePportionoftherecyclingfertilizersbythen(Table14).How-ever,comparedtocut1withPuptakesupto15mgperpot, Puptake at cut3was comparably low in all treat-ments.ThisindicatesthatplantavailablePreservesweremoreor lessusedupat that time.Thisassumptionwasstrengthened by the observation of signs of root decay(browncolor)ofdifferentextentfrompottopot,andbyamassivelyreducedbiomassproductioncomparedtocut1.The P content in the substrate determined by CAL-P,however,deliverednoadditionalevidence(seeFigure2).Recyclingtreatment7didnotproduceanybiomassafter
cut2.Thebestrecyclingtreatmentwasagainstruvite(tr.5) followedbyorgNPMBM (tr.2).Bonemeal (tr.1),meatandbonemealash(tr.3)andP-SSATC(tr.6)alldisplayedaverylowPuptake.Like changes in root morphology, P uptake of roots
variedconsiderablybetweenthedifferent fertilizer treat-ments(Table15).ThereexistedacleardifferencebetweenstandardmineralandrecyclingfertilizerswithregardtoPuptakeinrelationshiptothePlevel:Exceptfortreatment7(NPK-SSATC),onlythestandardmineralfertilizersshowedanincreaseinPuptakewithincreasingPlevel.
2 SincethezeroPtreatmentdidnotproduceanymorebiomassaftercut2,netPuptakeofshootsatcut3isidenticalwithgrossPuptake.
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 237
Table14:
MeannetPuptakeandutilizationrate(UR,in%ofPsupply,onlyforcut1)ofdrymatteryieldinthedifferentPfertilizertreatmentsfortheindi-vidualcuts
P level 20 P level 40 P level 60
Tr. P uptake (mg) UR (%) Tr. P uptake (mg) UR (%) Tr. P uptake (mg) UR (%)
Cut1
1 2.92a 15 1 2.82a 7 1 2.95a 5
5 2.95a 15 3 3.99a 10 3 3.81a 6
3 3.63a 18 5 4.07a 10 2 4.87a 8
2 3.64a 18 2 4.58a 11 5 5.1a 8
4 4.37a 22 4 4.83a 12 6 5.3a 9
6 5.00ab 25 6 5.3a 13 4 6.4a 11
11 7.2bc 36 9 10.1b 25 9 12.3b 21
8 8.2cd 41 7 10.7b 27 11 12.3b 21
9 8.7cd 43 8 10.9b 27 8 13.0b 22
7 8.7cd 44 11 11.9bc 30 7 13.1b 22
10 10.4d 52 10 14.2c 36 10 14.1b 23
Cut2
3 1.59a 7 1.01a 7 1.22a
6 1.60a 1 1.92ab 3 1.86ab
1 1.67ab 3 1.95ab 1 1.94ab
4 1.88ab 6 1.96ab 6 2.17abc
7 2.02abc 4 2.05b 4 2.49abcd
2 2.09abc 2 2.63bc 2 2.67bcde
9 2.12abc 5 2.83bcd 5 3.50cde
11 2.14abc 8 3.32cd 9 3.65def
5 2.23abc 9 3.46cd 11 3.87def
8 2.49bc 10 3.58cd 8 3.97ef
10 2.77c 11 3.74d 10 4.94f
Cut3
6 1.98a 7 0 7 0
3 2.11a 6 2.44a 3 2.37a
1 2.36ab 3 2.48ab 1 2.46a
7 2.49ab 1 2.57ab 6 2.63a
9 2.53ab 4 2.81ab 4 3.07a
11 2.54ab 12 3.37ab 9 3.80ab
4 2.57ab 8 3.43ab 2 3.81ab
2 2.68ab 9 3.51ab 12 4.02ab
12 2.76ab 2 3.74ab 11 4.22ab
8 2.95ab 10 3.82ab 8 4.25ab
10 3.38b 5 3.94ab 5 5.1b
5 3.48b 11 3.97b 10 5.3b
differentlettersindicatesignificantdifferencesbetweentreatments(Tukey,p<0.05)
Since the test substrate did not contain any P, P-CALcontentsattheendoftheexperimentshouldgiveanindi-cationifandtowhichextenttheplantavailableamounts
ofPsuppliedbyfertilizationwereinfactexhaustedbytheplants(seeabove).ThenetP-CALcontentwascalculatedbysubtractingtheP-CALcontentofthezeroPtreatment.
238
Figure3demonstratesthatPwasmoreorlesscompletelytakenupbyplantsonlyatP level20.Adirect compari-sonshows that,asexpected, standardmineral fertilizersdeliveredhigheramountsofCAL-solublePthanrecyclingfertilizers.TheonlyexceptionwasNPK-SSATC(tr.7),whichshowedveryhighCALcontents.Asexplainedabove,thissewagesludgeashbasedfertilizerwasenrichedwithtri-plesuperphosphatetomaintainapredefinedPcontent,inadditiontheproductcontainedKCl,whichexplainsitshighersolubility.Thewitheringoftheplantsaftercut1inthis treatmentcausedthehighexcesssubstrate-Pat theend of the trial. Apart from this treatment, the highestamount of plant-available P among the recycling fertil-izerswas supplied byOrgNPMBM, Org NPSSand struvite,whilethelowestamountsofplant-availablePcamefromP-SSATC,MBMAandorgNPBM.
Table15:
MeannetPuptakeofrootsinthedifferentfertilizertreatments
P level 20 P level 40 P level 60
Tr. P uptake (mg) Tr. P uptake (mg) Tr. P uptake (mg)
3 0.72a 8 0.21a 6 0.83a
6 0.89a 1 0.67ab 1 0.90a
2 0.94a 9 0.70ab 3 1.08a
1 0.99a 3 0.97abc 2 1.11a
11 1.19ab 2 1.19abc 5 1.48a
5 1.38ab 7 1.45abcd 4 2.03a
4 1.44ab 6 1.78bcd 11 3.55b
7 1.67ab 5 1.82bcd 7 3.81b
10 1.73ab 11 1.97bcd 8 4.23b
9 2.35b 4 2.11cd 10 4.94b
8 2.37b 10 2.60d 9 4.98b
differentlettersindicatesignificantdifferencesbetweentreatments(Tukey,p<0.05)
3.2.4 Relationship between chemical solubility and P up-take in the Neubauer trial
ThehighestPuptakeswererealizedbythoserecyclingfertilizerswhichdisplayedthehighestsolubilityinneutralammoniumcitrate(andcitricacid).Acorrelationanalysiswas performed to investigate the statistical relationship
Figure3:
Plant-availablenetPcontent(P-CAL)inthesubstrateofdifferentfertilizertreatmentsafterthefinalharvest(soiltestlevelA=low;fertilizerde-scriptionseeTable3)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
org NP (BM) org NP (MBM) MBMA org NP (SS) Struvite P-SSA(TC) NPK-SSA(TC) MCP SSP DAP pa RP
Fertilizer type
NetP
-CA
L(m
g/k
g)
P level 20 mg
P level 40 mg
P level 60 mg
upper limit of soil test level A
S. Kratz, S. Haneklaus, E. Schnug / Landbauforschung - vTI Agriculture and Forestry Research 4 2010 (60)227-240 239
betweenchemicalsolubilityofthefertilizersandPuptakeintheNeubauertrial.Table16showsthat–lookingatthemeanofall11testedtreatments–thestrongestcorrela-tionwas found betweenwater-soluble P and P uptake.Also,astrongcorrelationwasfoundbetweenPsolubilityin alkaline ammonium citrate (AAC) and P uptake, fol-lowed by solubility in water+neutral ammonium citrate(W+NAC).ThiswastruefortotalPuptake(allcuts)andPuptakeatcut1. Incontrasttothis,atcut2thestron-gestcorrelationwithPuptakewasfoundforPsolubilityinmineralacid,followedbywaterandammoniumcitrate,whileatcut3,extractionwithNACEUshowedthebestcor-relation,followedbythestrongerextractantsformic(FA)andcitricacid(CA).Thisresultmirrorsthestrongerinitialeffectofwater-solublefertilizersandtheslowreleaseofnon-watersolublePforms.Lookingseparatelyatstandardmineralorrecyclingfer-
tilizers, the extracts with ammonium citrate correlatedbestwithPuptake inthecaseofmineralfertilizers.Sig-nificantcorrelationswerefound,however,theywereonlyweak(Table17).
Table16:
Pearsoncorrelationcoefficients(r)fortherelationshipbetweenabsolute(MinA)/relativePsolubilityindifferentchemicalextractsandPuptakeinthepottrial,calculatedforall11testfertilizersincommon
Shoots cut 1 Shoots cut 2 Shoots cut 3 Roots Shoots cut 1 to 3 + roots
n 142 139 134 141 133
MinA-P(%) 0.494** 0.565** 0.368** 0.292** 0.619**
FA(%MinA) 0.541** 0.435** 0.472** 0.362** 0.552**
CA(%MinA) 0.489** 0.352** 0.458** 0.392** 0.503**
NACEU(%MinA) 0.590** 0.453** 0.488** 0.473** 0.615**
W+NACFN(%MinA) 0.704** 0.450** 0.402** 0.501** 0.684**
AAC(%MinA) 0.773** 0.451** 0.285** 0.531** 0.724**
W(%MinA) 0.849** 0.469** 0.310** 0.520** 0.777**
Significances:**=p<0.01,*=p<0.05
Table17:
Pearsoncorrelationcoefficients(r)fortherelationshipbetweenabsolute(MinA)/relativePsolubilityindifferentchemicalextractsandPuptakeinthepottrial,calculatedformineralfertilizers(Types9to11)
Shoots cut 1 Shoots cut 2 Shoots cut 3 Roots Shoots cut 1 to 3 + roots
n 48 48 48 48 48
MinA-P(%) 0.289* 0.193 0.257 0.025 0.239
FA(%MinA) 0.228 0.197 0.215 0.195 0.250
CA(%MinA) 0.180 0.217 0.239 0.181 0.230
NACEU(%MinA) 0.293* 0.218 0.243 0.202 0.295*
W+NACFN(%MinA) 0.295* 0.221 0.248 0.202 0.297*
AAC(%MinA) 0.278 0.247 0.281 0.195 0.297*
W(%MinA) 0.227 0.186 0.201 0.196 0.245
Significances:**=p<0.01,*=p<0.05
For the recycling fertilizers, the strongest correlationswithnetPuptake(shootsandroots)wereobservedforex-tractionswithcitricacid(CA),followedbyneutralammo-nium citrate (NACEU orW+NACFN).However, therewerealsocleardifferencesbetweenthefirstandthefinalyield:Whilethepositiveinitialeffectofwater-solublefertilizerswasseenatcut1,atcut3therewerestrongerrelation-shipsbetweenPuptakeandthemorepowerfulextract-antscitricacid(CA),NACEUandformicacid(FA)(Table18),confirming again that the prompt advantage of water-soluble P forms can be at least partly compensated byslowlyavailablePformswithtime.
240
Table18:
Pearsoncorrelationcoefficients(r)fortherelationshipbetweenabsolute(MinA)/relativePsolubilityindifferentchemicalextractsandPuptakeinthepottrial,calculatedforrecyclingfertilizers(Types1to7)
Shoots cut 1 Shoots cut 2 Shoots cut 3 Roots Shoots cut 1 to 3 + roots
n 84 81 76 84 76
MinA-P(%) -0.550** 0.303** 0.222 -0.365** -0.150
FA(%MinA) 0.414** 0.241* 0.469** 0.249* 0.395**
CA(%MinA) 0.590** 0.277* 0.488** 0.530** 0.722**
NACEU(%MinA) 0.479** 0.271* 0.480** 0.540** 0.625**
W+NACFN(%MinA) 0.588** 0.086 0.283* 0.518** 0.550**
AAC(%MinA) 0.611** -0.170 -0.060 0.516** 0.385**
W(%MinA) 0.865** -0.323** -0.093 0.461** 0.387**
Significances:**=p<0.01,*=p<0.05
4 Conclusions
Itcanbeconcludedfromtheclosecorrelationsbetweenvariouschemicalextractionmethodsfoundformineralaswellasorganicfertilizersthatitiseasilypossibletoreducethenumberofstandardmethodstothreeorfour.Thiswillbemuchmoredifficultforproductsfromsewagesludgeash.However,withregardtotheheterogeneityofthesematerialsitisquestionablewhethertheirqualitycanasyetbedefinedwithsufficientaccuracytomakethematrad-ablefertilizer,i.e.moredevelopmentandresearchontheproductionengineeringside(stabilityandabilitytocontrolthethermochemicalprocess)isnecessary.Thisshouldin-cludethequestiontowhichextentnewconstituentsun-predictablydevelopingduringthethermochemicalprocessimpairthedeterminationofPsolubilitywithconventionalchemicalextractionmethods.The statistical calculations on correlations between
chemical solubility and agricultural performance in theNeubauerpottrialconfirmedarelationshipbetweenwa-tersolubilityofafertilizerandits initialeffect,whilethemid-termeffectofnon-watersolublefertilizerswasbestdescribedbyanextractionwithammoniumcitrate.Sinceitiseasiertohandleinthelaboratory,theEUmethodofneutralammoniumcitrateextractionwithoutaprecedingwaterextractionisrecommended.Inordertoestimatethetradable total P contentofa fertilizer, it is suggested tomaintainthemineralacidextractionalreadypracticedonEUlevel.However,sincethismethodshowsclosecorrela-tionwith theaqua regiaextraction, it isalsopossible tochoosethelatteroneforso-calledtotalP.Anadvantageoftheaqua regiaextractisthefactthatthisisatthesametime thestandardmethod toquantify totalheavymetalcontentsinfertilizersandsoils.
References
Bundesgütegemeinschaft Kompost (1998) Methodenbuch zur Analyse vonKompost.Stuttgart:VerlAbfallNow,154p
DINEN13346:2001-4CharakterisierungvonSchlämmen–BestimmungvonSpurenelementenundPhosphor-ExtraktionsverfahrenmitKönigswasser.Berlin:Beuth
FinckA(1992)DüngerundDüngung:GrundlagenundAnleitungzurDüngungderKulturpflanzen.Weinheim:VCH,488p
SchnugE,HaneklausS,VogelW(1994)Determinationofenvironmentalele-mentsincontaminatedsoilbyaquaregiaextractionandX-rayfluorescencespectroscopy (X-RF). In: Etchevers BJD (ed) 15thWorld Congress of SoilScience,Acapulco,Mexico,July10-16,1994:transactions;vol.3a,Com-missionII:symposia.Mexico:InternSocSoilScience,pp509-516
MurphyJ,RileyJP(1962)Amodifiedsinglesolutionmethodforthedetermina-tionofphosphateinnaturalwaters.AnalChimActa27:31-36
Neubauer H, SchneiderW (1923) Die Nährstoffaufnahme der KeimpflanzenundihreAnwendungaufdieBestimmungdesNährstoffgehaltsderBöden.ZPflanzenernDüngungAWissTeil2:329-362
NeubauerH(1931)DieKeimpflanzenmethodenachNeubauerundSchneider.In:HoncampF(ed)DüngemittelundDüngung.Berlin:Springer,pp882-902,HandbuchderPflanzenernährungundDüngerlehre2
SchüllerH(1969)DieCAL-Methode,eineneueMethodezurBestimmungdespflanzenverfügbarenPhosphatsimBoden.ZPflanzenernBodenkd123:48-63
StraußR, BleiholderH, BommT vanden,Buhr L,HackH,HeßM,KloseR,MeierU,WeberE(1994)EinheitlicheCodierungderphänologischenEnt-wicklungsstadienmono-unddikotyler Pflanzen : erweiterteBBCH-Skala:Allgemein,Kulturen.Basel:Ciba-Geigy
VDLUFA (2007) Die Untersuchung von Düngemitteln. Darmstadt : VDLUFA-Verl,VDLUFA-MethodenbuchBandII
Legal norms
Düngemittelverordnung(DüMV)vom16.12.2008,BGBlI(60):2524-2581,ge-ändertam03.11.2004,Bundesgesetzblatt:Teil1/BundesministerderJu-stizI:2767
Düngeverordnung (DüV)–VerordnungüberdieAnwendungvonDüngemit-teln, Bodenhilfsstoffen und Kultursubstraten nach den Grundsätzen dergutenfachlichenPraxisbeimDüngenvom27.02.2007,Bundesgesetzblatt:Teil1/BundesministerderJustiz,p221
EU-VerordnungüberDüngemittelVO(EG)2003/2003v.13.10.2003,EU-Amts-blattL304,mitÄnderungsverordnungenVO(EG)Nr.2076/2004,EU-Amts-blattL359,S.25ff.undVO(EG)Nr.162/2007,AmtsblattderEuropäischenUnion2007/L51:7