As durum wheat productivity is affected by nitrogen fertilisation management in Central Italy

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ContentslistsavailableatSciVerseScienceDirect

European

Journal

of

Agronomy

j our na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / e j a

As

durum

wheat

productivity

is

affected

by

nitrogen

fertilisation

management

in

Central

Italy

Laura

Ercoli

a,∗

_,

_Alessandro

_Masoni

b

_,

_Silvia

_Pampana

b

_,

_Marco

_Mariotti

c

_,

_Iduna

_Arduini

b

a_Scuola_Superiore_Sant’Anna,_p.zza_Martiri_della_Libertà_33,₅₆₁₂₇_Pisa,_Italy

b_Dipartimento_di_Scienze_Agrarie,_Alimentari_e_{Agroambientali,}_via_del_Borghetto_80,₅₆₁₂₄_Pisa,_Italy c_Dipartimento_di_Scienze_Veterinarie,_viale_delle_Piagge_2,₅₆₁₂₄_Pisa,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received8May2012

Receivedinrevisedform26July2012 Accepted13August2012 Keywords: Triticumdurum Nfertilisation Nsplitting Nsource Nleaching

a

b

s

t

r

a

c

t

OptimisationofNfertilisationisacentralissueandgoalofappliedresearchinagriculturalsystems. Site-speciﬁcmanagementtechniquesareneededinordertocloselymatchavailabilitywith require-mentthroughoutcropcycleandtoreduceasmuchaspossibleenvironmentaldispersionofN.Lysimeter experimentswereconductedincentralItalyintwosubsequentseasonstoinvestigatetheresponseoftwo commercialdurumwheatcultivarstodifferentNfertilisersappliedbeforeseedingandattopdressing, andtosplitapplicationsofN.Grainyieldandyieldcomponents,NuptakeandNleachingwere deter-mined.Ammoniumsulphate(AS)andureacontainingthenitriﬁcationinhibitor3,4-dimetihylpyrazole phosphate(Entec®₄₆₎_were_applied_before_seeding;_AS,_ammonium_nitrate_sulphate_containing_the

nitriﬁcationinhibitor3,4-dimetihylpyrazolephosphate(Entec®_26),_and_urea_were_applied_at_5th_leaf

unfoldedstage.SixN-fertilisertreatmentswithatotalNamountof180kgNha−1_were_tested,_consisting

ofsplittingapplicationbeforeseeding,atGS15andGS30respectivelyof0-180-0,0-90-90,30-150-0, 30-75-75,60-120-0and60-60-60kgNha−1.Inbothyears,fertilisersplittingaffecteddurumwheatgrain yieldandNconcentration;variationsduetosplittingreached1tingrainyieldand7gkg−1_in_N

concentra-tionofgrain,correspondingto4%increaseinproteincontent.Highestgrainyield,proteinconcentration, nitrogenuseefﬁciency(NUE),andnitrogenuptakeefﬁciency(NUpE)wereobtainedwiththeapplication of30kgNha−1_before_seeding._The_yield_advantage_was_related_to_higher_number_of_kernels_per_spike,

resultingfromhighernumberoffertilespikeletsperspike.Grainyieldwasnotaffectedbynitrogensource appliedbeforeseeding,butwasmodiﬁedbytopdressingNfertiliser.Yieldincreasedby0.4tha−1with urea,comparedtoASandEntec®_26,_owing_to_a_greater_number_of_kernels_per_spike._Nitrogen_leaching

wascloselyrelatedtorainfall:totalamountofNlostduringwheatcyclewasalmostentirelyaccounted forNleachinginwinter,beforetopdressingNapplication.Asaconsequence,thequantityofNlostby leachingincreasedwiththeincreaseofNrateappliedbeforeseeding,whiletopdressingfertiliserdidnot affectlosses.

1. Introduction

OptimisationofmineralNfertilisationaimedtoincreaseNuse efficiencyisacentralissueandgoalofappliedresearchin agricul-turalsystems.Nitrogenuseefficiencyofworldwidecerealcrops wasestimatedtobenear33%(RaunandJohnson,1999),ranging from14to59%inwheat(Melajetal.,2003;López-Bellidoetal., 2005);whichsuggeststhatcurrentNstrategiesareextremely inef-ficient.

Nitrogenuseefﬁciency(NUE)incerealgrainproductionmay belowowingtolossesofNbyvolatilisation,denitriﬁcationand

∗ Correspondingauthor.Tel.:+39050883357;fax:+39050883215. E-mailaddress:[email protected](L.Ercoli).

leaching.Ammonium-basednitrogenfertiliserproductsare sus-ceptibletovolatilisationlossesofnitrogenifsurface-appliedand not incorporated. Bouwman et al. (2002) estimated that NH3 volatilisationlossesfromsyntheticNfertilisersappliedtoboth win-terandsummercropsamountsto7%inindustrialisedcountries. InEurope,fertiliserNlossesviadenitriﬁcationwereestimatedat 0.2–2.9%oftheNappliedtocereals(Kaiseretal.,1996).

Leachinglossesoccurwhenrainfallexceedscrop evapotranspi-rationanddownward watermovement throughthesoilproﬁle takesplace,whichcorrespondstothefall-winterperiodinhumid Mediterranean climate (Arregui and Quemada, 2006). Leaching N–NO3lossesfromdurumwheatcropwereestimatedincentral Italyat21–32kgNha−1yr−1,correspondingto12–22%ofthetotal Napplied(Ercoliet al.,2012).Nitrate leachingina 3-yearcrop rotationwheat–barley–rapeseedinsimilarconditionsinSpainwas

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estimatedat31–35kgNha−1y−1,or25–29%ofthetotalNapplied (ArreguiandQuemada,2006).Thus,asageneralrule,Nleachingin MediterraneanclimatecanberegardedasthegreatestsourceofN lossandthemajordeterminantoflowNutilisationefﬁciency.

Durumwheat is widely cultivated throughout the Mediter-raneanregion,wherethecropistypically plantedinNovember andharvestedatthebeginningofJuly.Heavyrainfallandlowcrop evapotranspirationratescanbeexpectedbetweenNovemberand March,resultinginhigherriskofNleachinglosses.Toreduce leach-inglosses,fertiliserapplicationshouldaimtomatchasmuchas possibletherequirementofplantNwiththeavailablenitrogenin soil,minimisingtheexcessofNinsoiluselesstotheplant.Thus, applicationshouldbethelatestpossiblecompatiblewiththestage ofdevelopmentthatstillpermitsrapidNuptake,inordertoreduce theopportunitiesforNlossesofunusedN(Raunetal.,2008).

Anumberofexperimentsinwintercerealhaveshownthatsplit applicationsofNfertiliserinvolvingequalquantitiesofNapplied beforeandafterseedingareagronomicalstrategiestoimproveN utilisationefﬁciency(Alcozetal.,1993;Deloguetal.,1998; López-Bellidoetal., 2005,2012;Dilz, 1988).Sowers etal. (1994)and

Strong(1995)foundthattheNfertiliserappliedinautumn,owing toincreasedNleaching,hadalowerefﬁciencythanwhenthe nitro-genwassplittedinfallandspring.Garrido-Lestacheetal.(2004)

observedthattimingandsplittingofNfertiliserinﬂuencedgrain proteincontent,whichpeakedwhenhalforone-thirdoftheNrate (150kgNha−1)wasappliedatstemelongation,andinsomecases whenNwasappliedonlyattillering.However,theeffectof split-tingNrateongrainqualitywasunclearinotherstudies(Ayoub etal.,1994;Garrido-Lestacheetal.,2005).Fuertes-Mendizábaletal. (2010)foundthatthesplittingofthesameNrateinthree amend-ments(stagesGS20,GS30,andGS37,accordingtoZadoksscale) insteadoftwo(stagesGS20andGS30)didnotmodifygrainyield butimprovedgrainproteincontent,indicatingthatalateN applica-tionmayhavemoreimpactonNmetabolismandNremobilisation thanonbiomassaccumulationandgrainyield.Ottmanetal.(2000)

showedhighergrainproteincontentswiththeapplicationofhigh Nratesatanthesis.

AnotherstrategytoreduceNleachinglossesandtoincreaseN utilisationefficiencyistheuseoffertilisersreleasingreducedand controlledamountofnitricN.Severalstudieshaveshown bene-ficialeffectsoftheuseofslowandcontrolled-releasefertilisers, stabilisedfertilisers and/ornitrificationand ureaseinhibitorsto enhanceproductivityofagriculturalandhorticulturalcrops(Prasad andPower,1995;Pasdaetal.,2001;Carreresetal.,2003).Inother studies,however,nopositiveresultshavebeenreported follow-ing theapplication of fertilisers that delay nutrient availability (Cartagena etal.,1995;Diezetal.,1997;ArreguiandQuemada, 2008).Inconsistenciesinresultsmayappearsincesoilproperties and/orclimaticconditionsaffectbothnutrient-releaseratesfrom fertilisers and processes leading toleaching and denitrification lossesandimmobilisationinsoil.

The present work was undertaken to determine the effects ofdifferentsourcesofNfertiliserdistributedbeforeseedingand topdressingandsplitapplicationsofNongrainyield,yield compo-nents,NuptakeandNleachingofdurumwheat,andtoidentifyN fertiliserandtypeofsplittingthatoptimisedNuptakeandretention inMediterraneanenvironments.

2. Materialandmethods

Lysimeterexperimentswereconductedintwosuccessive grow-ingseasons,2008–2009and2009–2010attheexperimentalstation oftheDepartmentofScienzeAgrarie,AlimentarieAgroambientali oftheUniversityofPisa,Italy,thatislocatedatadistanceof approx-imately10kmfromthesea(43◦40N,10◦19E)and3mabovesea

level.Theclimateofthesiteiscold,humidMediterraneanwith meanannualmaximumandminimumdailyairtemperaturesof 20.2and9.5◦C,respectively(Moonenetal.,2001).Forbothyears, dailyweatherdatawereobtainedfromameteorologicalstation locatedwithin100mfromtheexperimentalﬁelds.

Inbothyearsafullfactorialoftwodurumwheatvarieties,two Nfertilisersbeforesowing,threetopdressingNfertilisersandsix splitapplicationsofNwasreplicatedtwotimesandarrangedina randomised,complete-block design.Thedurumwheat(Triticum durum Desf.) varieties were Latinur and Svevo, currently used in local production. The two N fertilisers before sowing were ammonium sulphate (AS), and ureacontaining thenitriﬁcation inhibitor3,4-dimetihylpyrazolephosphate(Entec®_46)._The_three topdressing N fertilisers were AS, ammonium nitrate sulphate containingthenitriﬁcationinhibitor3,4-dimetihylpyrazole phos-phate (Entec® _26), _and _urea, _and _were _applied _at _the _5th _leaf unfolded stage.TotalNamountof180kgha−1 wassplit among pre-seeding,at5thleafunfoldedstageandatpseudostem erec-tionasfollows:0-180-0,0-90-90,30-150-0,30-75-75,60-120-0 and 60-60-60kgNha−1.Growthstages of5thleafunfolded and pseudo stem erection wereindividuated following the scale of Zadoks(Zadoksetal.,1974),correspondingrespectivelytoGS15 andGS30.

Open-air lysimeter installation consisted of 144 lysimeters of 0.50-m length, 0.50-m width and 0.4-m height (100-L vol-ume),arrangedinfourrowsof36,spaced20cmandembedded in expanded clay tosmooth daily ﬂuctuations in soil tempera-ture.Lysimeterswereﬁlledwithasoiltampedtoaboutoriginal soil bulk density,and wereattachedtoa 3-cmrigid PVCdrain thatendedinacentralcollectionfacility.Soilchemical–physical properties were: 68.5% sand (2mm>Ø>0.05mm); 25.9% silt (0.05m>Ø>0.002mm); 5.6% clay; 7.0 pH; 2.0% organic matter (Walkley andBlackmethod); 0.8gkg−1 totalnitrogen(Kjeldahl method);26.0mgkg−1 availableP(Olsenmethod);76.3mgkg−1 availableK(BaCl2+TEAmethod).

Phosphorusandpotassiumwerehandappliedpreplantingas triple mineral phosphate and potassium sulphate at a rate of 150kgha−1P2O5and150kgha−1K2O.Nitrogenwashandapplied beforeseedingandatGS15accordingtothetreatmentsandatGS30 asurea.

Thedurumwheatvarieties,LatinurandSvevo,weresownon 18November2008and25November2009,withintheoptimum plantingtimeforwheatproductioninCentralItaly.Arateof100 viableseedspercontainer,correspondingto400viableseedsm−2, in rows spaced15cm apart,wasapplied.Plant emergencewas recordedon5December2008and9December2009.Weedcontrol wasperformedthroughoutwheatcyclebyhandhoeing.

Leachatesfromeachlysimeterwerecollectedduringtheentire researchperiodinbothyearsaftereachmajorrainfalleventina 20-LPVCtank.LeachatevolumesweremeasuredandtheirN–NO3 concentrationsweredeterminedwithanOrionionanalysermodel 502A(OrionResearchInc.,Boston,MA,USA).Accumulatedmonthly leachatevolumeswerecalculatedandthemonthlyﬂow-weighted N–NO3 concentrationsweredeterminedbysummingupN–NO3 masscollectedforeachrainfalleventinamonthdividedbythe totalleachatevolumecollectedinthemonth.Averagely,a con-centrationof2.4mgN–NO3L−1wasdeterminedinrainfall.Forall treatments,timingofstageof1stleafemergence(GS10),5thleaf unfolded(GS15),pseudostemerection(GS30),inﬂorescence emer-gence (GS50),andphysiologicalripening(GS90)wererecorded, expressinginthermaltimethedurationoftheperiodsbetween stages(Table1).ThermaltimewascalculatedfollowingMcMaster and Wilhelm(1997),assuming2◦Casbasetemperature(Porter and Gawith,1999).At GS90 (22 June 2009 and 30 June 2010) plantsfromeachcontainerweremanuallycutatgroundleveland werepartitionedintoculms,leaves,chaffandgrain.Fordryweight

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Table1

Accumulatedgrowingdegreedaysandrainfallduringthewholewheatcycleand maingrowthperiods.GrowthstagesaredeﬁnedfollowingZadok’sscale(GS00 seed-ing,GS10emergence,GS155thleafunfoldedstage,GS30pseudostemerection,GS50 anthesis,GS90physiologicalmaturity).

Period GDD(◦_C) _Rainfall_(mm) 2008–2009 2009–2010 2008–2009 2009–2010 GS00–GS10 131.9 130.8 169.2 52.4 GS10–GS15 408.9 346.9 206.4 254.8 GS15–GS30 144.4 184.4 80.0 58.8 GS30–GS50 671.9 573.4 220.6 100.0 GS50–GS90 1048.7 1123.6 69.6 259.8 Wholecycle 2405.7 2358.9 745.8 725.8

determination,samplesfromallplantparts wereovendriedat 65◦Cuptoconstantweight.Meankerneldryweightwasalso mea-suredandnumberofkernelsperunitareaandharvestindex(HI) werecalculated.Samplesofeachplantpartwereanalysedfor nitro-genconcentration(Kjeldahlmethod);Ncontentswerecalculated bymultiplyingNconcentrationbydryweight.

Nitrogenefficiencyparameterswerecalculatedforeach treat-ment according to Moll et al. (1982) and López-Bellido et al. (2005).Nitrogenuseefficiency(kgkg−1)wastheratioofgrainyield biomasstoNfertiliser.Nitrogenuptakeefficiency(NUpE,kgkg−1) wastheratiooftotalaerialplantpartNuptaketoNfertiliser. Nitro-genutilisationefficiency(NUtE,kgkg−1)wastheratioofgrainyield biomasstototalNuptake.Nitrogenharvestindex(NHI)wasthe ratioofNingraintototalNuptake.

ResultsweretreatedbyANOVA.Themaineffectsofyear, vari-ety,Nfertiliserbeforeseeding,Nfertilisertopdressing,Nsplitting, andtheirinteractionsweretestedfordryweightofplantpartsand relativeNconcentrationandcontentandtotalNleached.Themain effectsofvariety,Nfertiliserbeforeseeding,Nfertilisertopdressing, Nsplitting,andtheirinteractionsweretestedfordrainagewater, NconcentrationandNleachinginthemonthsfromNovemberto Aprilin thetwoseasons. TheCoHortsoftwarepackagever. 6.4 (CoHortsoftware,Monterey,CA,USA)wasused.Signiﬁcantly dif-ferentmeanswereseparatedatthe0.05probabilitylevelbythe leastsigniﬁcantdifferencetest(Steeletal.,1997).

3. Results

3.1. Weatherconditions

Total rainfallduringwheatgrowingcyclewassimilarinthe 2008–2009and2009–2010growingseasons(Fig.1andTable1) andwasby42%highercomparedtothemeanrainfallforthearea overthelast 10 years(515mm).Rainfall fromseeding toGS30 wassimilarinbothyears,accountingforover50%oftotal rain-fallduringwheatcycle, whereasit differedduring jointingand grainﬁlling.Duringjointing,rainfallwasabout3-foldin2008–2009 comparedto2009–2010,whileduringgrainﬁlling itwasabout 3-foldin2009–2010compared to2008–2009.Temperaturewas lowerthanthelong-term averagein both seasons,asthe ther-maltimeuptomaturitywas2574◦Cinthelong-termaverage,vs. 2406◦Cin2008–2009and2359◦Cin2009–2010(Table1). Differ-encesbetweenseasonsinaccumulatedgrowingdegreedayswere recordedonlyintheperiodfromGS10toGS50.Thehighest differ-encebetweenseasonswasrecordedfromGS15toGS30,with28% highervaluein2009–2010comparedto2008–2009.

3.2. Grainyieldandyieldcomponents

Grain yields were always higher in 2009–2010 cropseason withallsplittings.Inbothgrowingseasonsthehighestyieldwas

Fig.1.Rainfall(bars),maximum(closedsymbol)andminimum(opensymbol) tem-peraturein2008–2009(up)and2009–2010(down)seasons.

obtainedwiththe30-150-0splitting,whiletheapplicationof 0-180-0in2008–2009and60-120-0in2009–2010resultedinthe lowestgrainyield(Fig.2).Differencesingrainyieldbetweenyears andsplittingswereduetovariationsinnumberofspikesperunit area,number ofkernelsperspikeandmeankernelweight.The averagenumberofspikesm−2was559in2009–2010seasonand 484in2008–2009(resultsnotshown)andwashigherwith 0-180-0andlowestwith60-60-60(Table2).Thenumberofkernelsper spikewashigherin2009–2010onlyfortheapplicationswithout Nbeforeseeding(0-180-0and0-90-90),whilefortheotherfour splittingsitwasthesameinthetwogrowingseasons(Fig.2).In bothyearsthehighestvalueswererecordedwith30-150-0, 60-60-60and30-75-75splittings,andlowestwith0-180-0.Maximum variationsduetodifferentsplittingswere8.4kernelsperspikein 2008–2009and6.1kernelsperspikein2009–2010.Meankernel weightdidnotvarybetweenyearswhilethehighestvaluesamong nitrogensplittingswereobtainedby30-75-75,60-60-60and 0-90-90treatments,andthelowestby60-120-0(Table2).Insummary, thehighestgrainyieldobtainedwiththetreatments30-150-0and 30-75-75derivedfromthecombinationoflownumberofspikes, highnumberofkernelsperspikeandmedium-highmeankernel weight.Conversely,thelowestgrainyieldrecordedinthe treat-ments0-180-0in2008–2009and60-120-0in2009–2010weredue

Table2

Harvestindex,spikenumber,andmeankernelweight.Nitrogensplittingmean values.

Nitrogensplitting Harvest index(%) Spikenumber (nm−2) Meankernel weight(mg) 0-180-0 33.3ab 595.6d 40.3b 0-90-90 37.2c 549.5c 41.4c 30-150-0 35.8bc 508.9b 40.2b 30-75-75 37.6c 494.9ab 41.8c 60-120-0 31.9a 509.4b 38.9a 60-60-60 36.3bc 468.8a 41.5c

Withincolumns,numbersfollowedbythesameletterarenotsigniﬁcantlydifferent atP≤0.05.

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Table3

Grainyield,vegetativedryweight,harvestindex,spikenumber,kernelnumberandmeankernelweight.Varietyandtopdressingnitrogenfertilisersmeanvalues. Treatments Grainyield(tha−1) Vegetatived.w.

(tha−1) Harvest index(%) Spikenumber (nm−2) Kernelnumber (nspike−1) Meankernel weight(mg) Variety Latinur 4.6b 8.2b 35.7a 555.9b 20.2a 41.9b Svevo 4.3a 7.9a 35.2a 486.5a 22.9b 39.4a

TopdressingNfertiliser

Ammoniumsulphate 4.4a 7.8a 36.0a 531b 20.6a 40.5a

Entec®₂₆ _4.2_a _8.1_b _33.9_a ₅₁₇_a _21.2_ab _40.6_a

Urea 4.7b 8.2b 36.4a 516a 22.8b 41.0a

WithintreatmentsvarietyandtopdressingNfertiliser,numbersfollowedbythesameletterarenotsigniﬁcantlydifferentatP≤0.05.

tothenumberofspikesthatwasmedium,thenumberofkernels perspikeandthemeankernelweightthatwerelow-medium.

GrainyieldofLatinurwas,onaverage,by7%higherthanthat ofSvevo(Table3).Theincreasewasattributedtoahighernumber ofspikesperunitarea(+14%),owingtoagreatertilleringrate,and meankernelweight(+6%).Conversely,numberofkernelsperspike ofSvevowasby13%higher.

Fig.2. Grainyield,vegetativedryweightandnumberofkernelsperspikeasaffected bycropseason×nitrogensplittinginteraction.Intheseandinthefollowingﬁgures, errorbarsindicateLDS.

Grainyieldwasnotaffectedbynitrogensourceappliedbefore seeding,butwasmainlymodiﬁedbytopdressingNfertiliser.Yield increasedby0.4tha−1 withurea,comparedtoASandEntec® ₂₆ averagevalue,owingtoagreaternumberofkernelsperspike(+9%) (Table3).

The response of thevegetative plant partto theinteraction year× splitting wasdifferentthan theoneof grain:dry weight washigherwith60-120-0and30-150-0splittingsandlowerwith 0-90-90 and 30-75-75 (Fig. 2).Differencesbetweenyears were detectedonlywithnoNfertiliserbeforeseeding,withhigher val-uesin2009–2010season.Dryweightofvegetativeplantpartwas higherinLatinurthaninSvevoandincreasedfromAStoEntec®₂₆ andurea(Table3).

HarvestIndexwasby17%higherin2009–2010comparedto 2008–2009seasonandwasmodiﬁedbyNsplitting,beinghighest with0-90-90and30-75-75andlowestwith60-120-0(Table2). DifferencesinHIbetweenvarietiesandtopdressingNfertiliser werenotstatisticallysigniﬁcant(Table3).

3.3. Nitrogenuptake

Nitrogenconcentrationofgrainandvegetativeplantpartwere signiﬁcantlyaffectedonlybytheinteractionyear×Nsplitting.The highest values were foundwith 0-90-90and 30-75-75 in both seasonsandwith0-180-0in2008–2009,andthelowestwith 0-180-0,30-150-0inbothseasonsandwith60-120-0in2009–2010 (Fig.3).FollowingthepatternsofdryweightandNconcentration, Ncontentofgrainandvegetativeplantpartwereaffectedbythe interactionyear×Nsplittingandbythemeaneffectof topdress-ingNfertiliser.Excludingthe60-120-0split,thehighestvaluesof grainNcontentwererecordedin2009–2010seasonatall split-tings,butwhilein2008–2009differencesamongsplittingswere low(max.18kgNha−1),in2009–2010thesplittings0-90-90, 30-75-75and60-60-60gavevaluesby28kgNha−1highercompared totheothersplittings(Fig.3).GrainNcontentincreasedfromAS to Entec® ₂₆ _(8.0%) _and _to_urea _(13.6%), _even _though_between theselasttwothenon-signiﬁcantincreaseduetotheureawasof 5.1kgNha−1(Table4).DifferencesforNcontentinvegetativeplant partwerealsodetected(Fig.3andTable4).Asaconsequence,total Nuptakebyaerialplantpartwasby34kgNha−1higherwith 0-90-90,30-75-75and60-60-60in2009–2010comparedtotheother

Table4

Nitrogencontentofgrainandvegetativeplantpart.Topdressingnitrogenfertiliser meanvalues.

TopdressingNfertiliser Nitrogencontent(kgha−1₎

Grain Vegetativeplantpart

Ammoniumsulphate 92.1a 36.9ab

Entec®₂₆ _99.5_ab _34.8_a

Urea 104.6b 37.8b

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Fig.3.Nitrogenconcentrationandcontentofgrainandvegetativeplantpartasaffectedbycropseason× nitrogensplittinginteraction.

splittings(Fig.3)andby13kgNha−1higherwithureacompared toAS(Table4).NUEwasaffectedbytheinteractionyear×splitting, andhadthesamepatternofgrainyield,beingtherateoffertiliser Nthesameforalltreatments(Table5).Similarlytograinyield, highestNUEwasachievedinbothyearwiththe30-150-0and 30-75-75splittings.Theseasoninﬂuenced alsoNUpEand NUtE.In 2008–2009variationsduetosplittreatmentsonbothindiceswere inconsistent,whilein2009–2010NUpEincreasedappreciablywith treatmentsinvolvinghigherNratesatGS30(0-90-90,30-75-75 and60-60-60),whileNUtEwashigherwhenhigherNrateswere appliedatGS15(0-180-0,30-150-0and60-120-0)(Table5).The proportionoftotalplantNintheseedsatmaturity(NHI)waslowest whenthesecondtopdressingfertilisationwasnotapplied(Fig.4).

3.4. Nitrogenleaching

The amountofdrainagewater recordedinthemonthsfrom NovembertoAprilwasnotaffectedbyanyofthetestedtreatments, but washigher during the 2008–2009crop season(430.3mm) comparedtothe2009–2010season(389.9mm).Highest percola-tionsoccurredin December2009and inDecemberandJanuary

Table5

Nitrogenuseefficiency(NUE),nitrogenuptakeefficiency(NUpE)andnitrogen util-isationefficiency(NUtE).Season×nitrogensplittinginteraction.

Season Nsplitting NUE

(kgkg−1₎ NUpE (kgkg−1₎ NUtE (kgkg−1₎ 2008–2009 0-180-0 18.1a 0.64a 28.4ab 0-90-90 20.6b 0.74bc 27.7a 30-150-0 23.6cd 0.73bc 32.3cd 30-75-75 22.5bc 0.75c 30.1abc 60-120-0 21.6bc 0.67abc 32.4cd 60-60-60 22.3bc 0.66ab 34.0d 2009–2010 0-180-0 27.1f 0.73bc 37.4e 0-90-90 27.0ef 0.91d 29.7abc 30-150-0 30.1g 0.76c 39.6e 30-75-75 28.6fg 0.91d 31.2bcd 60-120-0 24.9de 0.65ab 38.3e 60-60-60 27.8f 0.87d 31.8cd

Fig.4. Nitrogenharvestindexasaffectedbynitrogensplittingmeaneffect.

2010 (Fig. 5).High rainfall determinedhigh drainagefew days following pre seeding N application in the 2008–2009 season, while in 2009–2010drainage started aboutone month follow-ingNapplication.InNovember,DecemberandJanuary,drainage wateraccountedfor61%and80%oftotaldrainage,respectivelyin

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Fig.6.Nitrogenconcentrationindrainageandnitrogenleachedduring2008–2009and2009–2010seasonsasaffectedbynitrogensplittingmeaneffect.

2008–2009and2009–2010seasons.Theamountofdrainagewater wasclosetozerofollowingthesecondtopdressingfertilisation.

Inbothseasons,nitrogenconcentrationindrainagewaterand leachedNwereaffectedonlybyNsplitting.Nitrogenconcentration inwaterwashigherfollowingseedinganddecreaseduntilJanuary inbothyearsatallsplittings(Fig.6).Inthisperiod,Nconcentration increasedwiththeincreaseofNratebeforeseeding.Thereafter, valueswerelowerthan4mgNL−1andunaffectedbyNsplitting.

Averaged over all treatments, total amount of N lost with drainagewaterduringwheatcyclewasalmostentirelyaccounted forNleachinginDecember(63%and74%ofthetotalleachedN, respectivelyinthe2008–2009and2009–2010seasons)(Fig.6). IntheperiodfollowingﬁrsttopdressingNdistribution,Nleached accountedfor17%and4%oftotalNlostrespectivelyfor2008–2009 and 2009–2010 seasons. The quantity of N lost in both years increasedwiththeincreaseofNrateappliedbeforeseeding,while topdressingfertiliserdidnotaffectlosses(Fig.7).WhenNwasnot appliedbeforeseeding,Nlostwaslowandsimilarinthetwo sea-sons,whilewiththeothersplittingsNlostwashigherin2008–2009 comparedto2009–2010season.

Fig.7. TotalNleachedduring2008–2009and2009–2010seasonsasaffectedby nitrogensplittingmeaneffect.

4. Discussion

4.1. Nitrogenfertiliseratsowing

The applicationof SAand Entec® ₄₆ _before_seeding _did_not modifyeithergrainyieldandyieldcomponentsorNuptakeand leaching,indicatingthatinthisresearchtheinclusionofthe nitri-ficationinhibitordidnotshowanyadvantageincomparisonwith ammoniumfertiliser.Nitrificationinhibitorshavebeenshownto increaseyieldwhenthefertiliserisappliedinconditionsthatfavour nitratelossesbyleaching,thatis,inperiodsofhighrainfallor irriga-tion,orinsandyorhighlypermeablesoils(PrasadandPower,1995; Barthetal.,2001).Conversely,inotherstudiestheyieldadvantage wasnullorsmall,averagingjust5%,duetotheapplicationofN whenleachingwaslowandwhencropdemandwashigh(Hergert andWiese,1980;Pasdaetal.,2001;ArreguiandQuemada,2006, 2008).Inthisresearch,theapplicationofthenitrificationinhibitor wasperformedwhenleachingwashighandcropdemandwaslow, whichareconditionsthatwouldfavourtheinclusionof nitrifica-tioninhibitorsinfertiliser.Neverthelessnitrificationinhibitorwas notsuccessfultocontrolnitrateleachingduringtheperiodofhigh rainfall.

4.2. Nitrogensplitting

Climatic conditionsduring growingseasoninﬂuenced wheat grainyield,asinthe2008–2009theaveragegrainyieldwasby22% lowerthanin2009–2010.Thehighyieldin2009–2010wasdueto highernumberofspikesandgreaterspikesize,probablybecause ofgoodgrowingconditionsduringinitialstagesofcrop develop-mentthatfavouredthedevelopmentoftillersandpromotedthe ﬂoretfecundation,resultinginhighernumberofkernelsperspike. Fertilisersplittinginbothyearshadaconsiderableimpactongrain yieldandyieldcomponents.Theobserveddifferencesingrainyield andyieldcomponentscausedbytheinteractiveeffectsofdifferent Nsplittingsandweatherconditionsmaybeduetoprocessesinsoil andinplantaffectingNavailabilityincriticalphasesof determina-tionofyieldcomponents.Owingtotheschemeoftreatments(equal

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totalNrate,butdifferentsplittings)theeffectofthedifferentrates indifferentphasescannotbeseparatedinourresults,andattempts toclarifycausescanonlybeconsideredaspossiblereasons. Nev-ertheless,itwasdemonstratedthatitispossibletoimprovegrain yieldandNconcentrationbyvariationsinsplitapplicationsof fer-tiliserN:thevariationsduetosplittingreached1tingrainyield whiletheproteingraincontentincreasedby4%,correspondingto 7gkg−1 in Nconcentrationofgrain.Comparingtheeffectofall splittings,thehighestgrainyield(andNUE)andthehighest pro-teinconcentration(andNUpE)wereobtainedwith30-150-0and 30-75-75treatments,respectively.Theyieldadvantagewasrelated tothehighernumberofkernelsperspikeresultingfromthehigher numberofdifferentiatedspikeletsperspike.Thus,theapplication of30kgNha−1beforeseedingisrequiredtohavehighgrainyield, asmineralNinsoilderivingfrommineralisationofsoilorganic matterandnotleachedprobablywasnotsufficienttoensurehigh yield.Theothercharactersweredifferentlyaffectedby differen-tialNavailabilityduringcropgrowth,asyieldcomponentsvaried amongsplittreatmentsinthetwoseasons.TheapplicationofNonly topdressing(0-180-0and0-90-90)greatlyreducedgrainyieldby thereductionofthenumberofkernelsperspike.Theeffectwas par-ticularlyheavyintheseasonwithhighrainfallbeforeseeding,when themineralNamountpresentinthesoilatthetimeoffertiliser applicationwasverylowowingtoNleaching.Inthetreatment 0-180-0highNrateatGS15stimulatedtillering,butNdeficiency occurredduringthelastpartofwheatcycle(NappliedatGS15 wasprobablyimmobilisedintosoilandnotavailablethereafter). Nitrogenrestrictionduringthelastpartofwheatcycle(0-180-0, 30-150-0,60-120-0)leadtoareducedNaccumulationintograin, andfor60-120-0alsoareductionofcarbohydrateaccumulation intograin.Thismeansthatgraingrowthwasprobablyconstrained byNshortageduringgrainfilling.SinceNleachingincreasedwith theincreaseoftherateofNappliedbeforeseeding,itislikelythat theloweryieldwith60-120-0comparedto0-180-0isduetolower NavailabilityduetoNleached.

Insummary,theapplicationofNonlytopdressingisnotavalid optionsincesoilmineralNisnotsufﬁcienttosustainNuptake intheﬁrstthreemonthsofcropgrowth,whenrainfalland con-sequentlyNleachingarehigh.Conversely,theapplicationofthe highest rate (60kgNha−1) before seeding is not to be recom-mended,sinceitposesseriousenvironmentalconcernsowingto highriskofleachinglosses.Moreover,theapplicationofNintwo ratesbeforeseedingandtopdressingatearlycropstagesisalso notadvisable,sincedrymatterandNaccumulationintograinis reduced.ThesplittingoftheNrateinthreeamendmentsinstead oftwo withthethirdapplication atlater cropstageleadtoan increaseofgrainproteincontent,suggestinganimprovementof grainqualityparameters.

4.3. Topdressingnitrogenfertilisers

NsourceappliedtopdressingatGS15affectedgrainyieldand yieldcomponents,aswellasdryweightofvegetativeplantpart and N uptake. Conversely, N leaching was not affected as the weatherconditionsandthecropevapotranspirationfollowing fer-tiliserapplicationdidnotpromoteNO3−leaching.Indeed,water drainagewascloselyrelated torainfall,whichwasnegligiblein theperiodfollowingtopdressingNapplication.Theapplicationof urearesultedinthehighestgrainyield,owingtoagreaternumber ofkernelsperspikethatcompensatedthelowernumberofspikes perunitarea.Indurumwheat,spikeinitiationoccursintheperiod fromthedevelopmentofthe4thleaf,GS14,tostemelongation, GS(Arduinietal.,2009)andthenumberofinitiatedspikeletsis enhancedinpresenceofagoodNavailabilityinsoil(Masonietal., 2001).OurresultssuggestthattheprompterreleaseofNfromurea comparedtoASandEntec®₂₆_increased_N_available_in_the_period_of

floretinitiationanddifferentiation.Mulvaney(1994)showedthat nitrificationoccurredintheorderurea>AS.Likewise,EnoandBlue (1957)andMartikainen(1985)reportedthatureanitrifiesfaster thanAS.Thisdifferentialinnitrificationratehasbeenattributedin parttotheincreaseinsoilpHassociatedwiththehydrolysisofurea soonafterapplication,incontrasttothedeclineinsoilpH associ-atedwiththeapplicationofAS(Lindsayetal.,1962;Allredand Ohlrogge,1964).TheeffectofEntec® ₂₆_on_grain_yield_and_yield componentswassimilartothatofAS,thusthedelayedeffectofthe nitrificationinhibitorDMPPonNH4+nitrificationdidnotbenefit wheatgrowth.Entec®₂₆_contains_7.5%_NO

3–Nand18.5%NH4–N, whileAScontainsallnitrogeninNH4+form.Theprobablehigher persistenceofNH4+insoilinEntec®26thaninASplotshadnotany advantageforcropgrowthandthereductionofN–NO3duetothe inhibitionofnitriﬁcationinEntec®₂₆_compared_to_AS_is_probably compensatedbythepresenceofnitricN.Inaddition,wecannot excludethatpartofNH4+maybeﬁxedinclayminerals(Gioacchini

etal.,2006),thusreducingNavailabilitytoplants.

5. Conclusions

Ourresultsevidencednoclearadvantageofthedistributionto durumwheatofEntec®₄₆_before_seeding,_and_Entec®₂₆ topdress-ing,neitherintermsofincreasedgrainquantityandquality,nor intermsofhigherNutilisationefficiencyanddecreasedN leach-ing.SinceNfertiliserapplicationrepresentsanimportantcostin cropproductionandfertiliserscontainingthenitrificationinhibitor DMPPhavehigherpricesthanSAorurea,theiruseisnot advis-able in Central Italy. Further researches should investigate the applicationtodurumwheatofotherdelayed-releaseNfertilisers, focussingonthemechanismsofNreleaseinfieldconditions,in ordertosynchroniseitwithplantdemand.

ThesplittingofNfertiliseriscrucialtoimprovefertiliseruse effi-ciencyandtoincreasegrainyieldandgrainproteinconcentration. Theapplicationof30kgNha−1 beforeseedingis recommended, sincemineralisationofsoilorganicmattercouldnotensure ade-quatemineralNavailabilityforinitialcropdevelopment,resulting inagreatreductionofkernelnumberperspikeandconsequently grain yield. Conversely, 60kgNha−1 before seeding proved to exceedcropneeds,resultinginincreasedNleachingduringinitial cropstageandNdeficiencyatlatercropdevelopment.Topdressing distributioncanberecommendedbothentirelyat5thleafor split-tedhalfat5thleafandhalfatstemelongation.Inourresearch,the firstsplitting,i.e.30-150-0,gavethehighestgrainyieldwhilethe second,30-75-75,gavethehighestNconcentrationingrain.Finally, thedistributionofureaat5thleafisadvisablebecause,compared toammoniumsulphateandEntec®_26,_it_turned_into_higher_grain yieldwithlowerdistributioncosts.

References

Alcoz,M.M.,Hons,F.M.,Haby,V.A.,1993.Nitrogenfertilizationtimingeffecton wheatproduction,nitrogenuptakeefﬁciency,andresidualsoilnitrogen. Agron-omyJournal85,1198–1203.

Allred,S.E.,Ohlrogge,A.J.,1964.Principlesofnutrientuptakefrombands.VI. Ger-minationandemergenceofcornasaffectedbyammoniaandammonium phosphate.AgronomyJournal56,309–313.

Arduini,I.,Ercoli,L.,Mariotti,M.,Masoni,A.,2009.Sowingdateaffectspikelet numberandgrainyieldofdurumwheat.CerealResearchCommunications37, 469–478.

Arregui,L.M.,Quemada,M.,2006.Drainageandnitrateleachinginacroprotation underdifferentN-fertilizerstrategies:applicationofcapacitanceprobes.Plant andSoil288,57–69.

Arregui,L.M.,Quemada,M.,2008.Strategiestoimprovenitrogenuseefﬁciencyin wintercerealcropsunderrainfedconditions.AgronomyJournal100,277–284. Ayoub,M.,Guertin,S.,Fregeau-Reid,J.,Smith,D.L.,1994.Nitrogenfertilizereffecton breadmakingqualityofhardredspringwheatineasternCanada.CropScience 34,1346–1352.

(9)

Barth,G.,vonTucher,S.,Schmidhalter,U.,2001.Inﬂuenceofsoilparameterson theeffectof3,4-dimethylpyrazole-phosphateasanitriﬁcationinhibitor.Biology andFertilityofSoils34,98–102.

Bouwman,A.F.,Boumans, L.J.M.,Batjes, N.H.,2002. Estimationofglobal NH3

volatilizationlossfromsyntheticfertilizersandanimalmanureappliedtoarable landsandgrasslands.GlobalBiogeochemicalCycles16,1024–1037.

Carreres,R.,Sendra,J.,Ballesteros,R.,Valiente,E.F.,Quesada,A.,Carrasco,D.,Leganés, F.,Cuadra,J.G.,2003.Assessmentofslowreleasefertilizersandnitriﬁcation inhibitorsinﬂoodedrice.BiologyandFertilityofSoils39,80–87.

Cartagena,M.C.,Vallejo,A.,Diez,J.A.,Bustos,A.,Caballero,R.,Roman,R.,1995.Effect ofthetypeoffertilizerandsourceofirrigationwateronNuseinamaizecrop. FieldCropsResearch44,33–39.

Delogu,G.,Cattivelli,L.,Pecchioni,N.,DeFalcis,D.,Maggiore,T.,Stanca,A.M.,1998. Uptakeandagronomicefﬁciencyofnitrogeninwinterbarleyandwinterwheat. EuropeanJournalofAgronomy9,11–20.

Diez,J.A.,Roman,R.,Caballero,R.,Caballero,A.,1997.Nitrateleachingfromsoils underamaize–wheat–maizesequence,twoirrigationschedulesandthreetypes offertilisers.Agriculture,Ecosystems&Environment65,189–199.

Dilz,K.,1988.Efﬁciencyofuptakeandutilizationoffertilizernitrogenbyplants.In: Jekinson,D.S.,Smith,K.A.(Eds.),NitrogenEfﬁciencyInAgriculturalSoils.Elsevier AppliedScience,London,pp.1–26.

Eno,C.F.,Blue,W.G.,1957.Thecomparativerateofnitriﬁcationofanhydrous ammo-nia,urea,andammoniumsulfateinsandysoils.SoilScienceSocietyofAmerica Proceedings21,392–396.

Ercoli,L.,Arduini,I.,Mariotti,M.,Lulli,L.,Masoni,A.,2012.Managementof sul-phurfertilisertoimprovedurumwheatproductionandminimiseSleaching. EuropeanJournalofAgronomy38,74–82.

Fuertes-Mendizábal,T.,Aizpurua,A.,González-Moro,M.B.,Estavillo,J.M.,2010. ImprovingwheatbreadmakingqualitybysplittingtheNfertilizerrate.European JournalofAgronomy33,52–61.

Garrido-Lestache,E.,López-Bellido,R.J.,López-Bellido,L.,2004.EffectofNrate, tim-ingandsplittingandNtypeonbread-makingqualityinhardredspringwheat underMediterraneanconditions.FieldCropsResearch85,213–236.

Garrido-Lestache,E.,López-Bellido,R.J.,López-Bellido,L.,2005.Durumwheat qual-ityunderMediterraneanconditionsasaffectedbyNrate,timingandsplitting, NformandSfertilization.EuropeanJournalofAgronomy23,265–278. Gioacchini,P.,Ramieri, N.A.,Montecchio, D.,Marzadori,C.,Ciavatta,C.,2006.

Dynamicsofmineralnitrogeninsoilstreatedwithslow-releasefertilizers. Com-municationsinSoilScienceandPlantAnalysis37,1–12.

Hergert,G.W.,Wiese,R.A.,1980.Performanceofnitriﬁcationinhibitorsinthe Mid-west(west).In:Meisinger,J.J.,Randall,G.W.,Vitosh,M.L.(Eds.),Nitriﬁcation Inhibitors:PotentialsandLimitations,vol.38.Am.Soc.Agron.,Madison,WI,pp. 89–105(Spec.Publ.).

Kaiser,E.A.,Eiland,F.,Germon,J.C.,Heinermeyer,R.O.,Henault,C.,Lind,A.M.,Maag, M.,Saguer,E.,VanCleemput,O.,Vermoesen,A.,Webster,C.,1996.What pre-dictsnitrousoxideemissionsanddenitriﬁcationN-lossfromEuropeansoils? ZeitschriftfürPﬂanzenernahrungundBodenkunde159,541–547.

Lindsay, W.L., Frazier,A.W., Stephenson, H.F., 1962. Identiﬁcation of reaction productsfromphosphatefertilizersinsoils.SoilScienceSocietyofAmerica Proceedings26,446–452.

López-Bellido,L.,López-Bellido,R.J.,Redondo,R.,2005.Nitrogenefﬁciencyinwheat underrainfedMediterraneanconditionsasaffectedbysplitnitrogenapplication. FieldCropsResearch94,86–97.

López-Bellido, L., Mu ˜noz-Romero, V., Benítez-Vega, J., Fernández-García, P., Redondo,R.,López-Bellido,R.J.,2012.Wheatresponsetonitrogensplitting appliedtoavertisolsindifferenttillagesystemsandcroppingrotationsunder typicalMediterraneanconditions.EuropeanJournalofAgronomy43,24–32. Martikainen,P.J.,1985.NitriﬁcationinforestsoilofdifferentpHasaffectedbyurea,

ammoniumsulphateandpotassiumsulphate.SoilBiologyandBiochemistry17, 363–367.

Masoni,A.,Arduini,I.,Mariotti,M.,Ercoli,L.,Bonari,E.,2001.Numberofspikelets andleafappearancerateindurumwheatasaffectedbytemperature,daylength andnitrogenavailability.AgricolturaMediterranea130,57–65.

McMaster,G.S.,Wilhelm,W.W.,1997.Growingdegree-days:oneequation,two interpretations.AgriculturalandForestMeteorology87,291–300.

Melaj,M.A.,Echeverría,H.E.,López,S.C.,Studdert,G.,Andrade,F.,Bárbaro,N.O., 2003.Timingofnitrogenfertilizationinwheatunderconventionalandno-tillage system.AgronomyJournal95,1525–1531.

Moll,R.H.,Kamprath,E.J.,Jackson,W.A.,1982.Analysisandinterpretationofis fac-torswhichcontributetoefﬁciencyofnitrogenutilization.AgronomyJournal74, 562–564.

Moonen,C.,Masoni,A.,Ercoli,L.,Mariotti,M.,Bonari,E.,2001.Long-termchanges inrainfallandtemperatureinPisa,Italy.AgricolturaMediterranea131,11–22. Mulvaney,R.L.,1994.Nitriﬁcationofdifferentnitrogenfertilizers.In:Hoeft,R.G. (Ed.),IllinoisFertilizerConferenceProceedings.CooperativeExtensionService, UniversityofIllinois,Urbana,IL,pp.83–96.

Ottman,M.J.,Doerge,T.A.,Martin,E.,2000.Durumgrainqualityasaffectedby nitro-genfertilizationnearanthesisandirrigationduringgrainﬁll.AgronomyJournal 92,1035–1041.

Pasda,G.,Hahndel,R.,Zerulla,W.,2001.Effectoffertilizerswiththenew nitriﬁca-tioninhibitorDMPP(3,4-dimethylpyrazolephosphate)onyieldandqualityof agriculturalandhorticulturalcrops.BiologyandFertilityofSoils34,85–97. Porter,J.R.,Gawith,M.,1999.Temperaturesandthegrowthanddevelopmentof

wheat:areview.EuropeanJournalofAgronomy10,23–36.

Prasad,R.,Power,J.F.,1995.Nitriﬁcationinhibitorsforagriculture,health,andthe environment.AdvancesinAgronomy54,233–281.

Raun,W.R.,Solie,J.B.,Taylor,R.K.,Arnall,D.B.,Mack,C.J.,Edmonds,D.E.,2008.Ramp calibrationstriptechnologyfordeterminingmidseasonnitrogenratesincorn andwheat.AgronomyJournal100,1088–1093.

Raun,W.R.,Johnson,G.V.,1999.Improvingnitrogenuseefﬁciencyforcereal pro-duction.AgronomyJournal91,357–363.

Sowers,K.E.,Miller,B.C.,Pan,W.L.,1994.Optimizingyieldandgrainproteinin softwhitewinterwheatwithsplitnitrogenapplications.AgronomyJournal86, 1020–1025.

Steel,R.G.D.,Torrie,J.H.,Dickey,D.A.,1997.PrinciplesandProceduresofStatistics: ABiometricalApproach.McGraw-Hill,NewYork.

Strong,W.M.,1995.Nitrogenfertilizationofuplandcrops.In:Bacon,P.E.(Ed.), Nitro-genFertilizationintheEnvironment.MarcelDekker,NewYork,pp.129–169. Zadoks,J.C.,Chang,T.T.,Konzak,C.F.,1974.Adecimalcodeforthegrowthstagesof