Management of sulphur fertiliser to improve durum wheat production and minimise S leaching

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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

Management

of

sulphur

fertiliser

to

improve

durum

wheat

production

and

minimise

S

leaching

Laura

Ercoli

a,∗

_,

_Iduna

_Arduini

b

_,

_Marco

_Mariotti

b

_,

_Leonardo

_Lulli

b

_,

_Alessandro

_Masoni

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

b_Dipartimento_di_Agronomia_e_Gestione_{dell’Agroecosistema,}_via_S._Michele_degli_Scalzi_2,₅₆₁₂₄_Pisa,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received4October2011 Receivedinrevisedform 24November2011 Accepted19December2011 Keywords: Triticumdurum Sulphurfertilisation Sulphurleaching Sulphurbalance

a

b

s

t

r

a

c

t

OptimisationofSreleasefromdecomposingsoilorganicmatterandSfertiliserrelatedtoplantSuptake isacentralissueandgoalinappliedresearchinagriculturalsystems.Twolysimeterexperimentswere conductedincentralItalyintwosubsequentseasonsontwocommercialdurumwheatcultivarsto investigatetheeffectsonyield,SandNuptakeandleachingofdifferentratesofNandSfertilisers, soiltypeandsplitapplicationsofS.SulphurfertiliserincreasedgrainyieldandNandSuptakeofboth varieties.Grainyieldincreasewasmainlyduetoanincreaseofthenumberofkernelsperspike,which wasinterpretedasastimulationoftheinitiationofspikeletsand/orflorets,ortoareductionthefloret mortality.Asanaverageofthetwoseasons,Sleachingduringwheatcyclewas35kgSha−1_._Sulphur fertiliserrateincreasedSconcentrationindrainagewaterandconsequentlySleachedduringwheatcycle. Comparedtounfertilisedcontrol,Sleachedwasby13kgha−1higherat60kgSha−1andby19kgha−1 higherat120kgSha−1_._The_splitting_of_sulphur_fertiliser_during_crop_cycle_modified_both_grain_yield andSleaching.ThehighestgrainyieldandSplantuptakewasobtainedwiththesplittingofSrate into60kgSha−1beforeseedingand60kgSha−1atstemelongationandthelowestamountofSlostby leachingoccurredwiththeapplicationof36kgSha−1_before_seeding_and₈₄_kg_S_ha−1_at_stem_elongation. Sulphuroutputwasequallyaccountedforbyleachingandplantuptake.Theinput–outputbalanceofS waspositiveinbothexperimentsonlywhenthehigherSratewasapplied,asmoreSwasimportedthan removed.Thus,nosubstantialSdeficitmaybeexpectedinshortterm,providedthathighSfertiliserrate isappliedandtheavailabilityofSissynchronisedwithplantneeds.

1. Introduction

Sulphurisanessentialnutrientforplantssinceitisinvolvedin

keystepsofplantmetabolism.Duringthelastdecades,sulphur

deﬁciencyinagriculturalsoilshasbecomewidespreadin many

Europeancountries.ThisismainlycausedbythereductionsinSO2

emissions,theuseoflowS-containingfertilisers,thelowSreturn

withfarmyardmanure,andthedeclininguseofS-containing

fungi-cides(Schnug,1991;deRuiterandMartin,2001;Scherer,2001).

Fordurumwheat,itiswellestablishedthatSdeﬁciencycan

adverselyaffectplantgrowthandgrainqualitythroughitseffect

onprotein composition(Lerneretal.,2006;Ercoliet al.,2011).

Theresponseofwheattosulphurfertiliserwasfoundtovary

con-siderably betweensitesand years, due todifferences insoil or

climaticconditions(Pedersenetal.,1998).Especiallyvariationsin

soilorganicmattercompositionaswellaswinterrainfallandspring

∗ Correspondingauthor.Tel.:+39050883357;fax:+39050883215. E-mailaddress:ercoli@sssup.it(L.Ercoli).

temperaturemaygivedifferencesinthelevelofsulphateavailable

atthetimeofplantdemand(EriksenandAskegaard,2000).

Sulphurispresentinsoilininorganicandorganicforms,the

formerbeinggenerallymuch lessabundantinmostagricultural

soils,accountingforlessthan10%ofthetotalS(Bohnetal.,1986).

SulphateisthemostcommonformofinorganicSinsoilandcan

bepresentasSO42−eitherdissolvedinsoilsolutionoradsorbed

tosoilparticlesandinsolublesulphur(Barber,1995).Soilorganic

SexistsasC-bondedSorassulphateesters(Eriksen,2009).The

sulphurstockinsoilissubjecttobioticprocesses,causing

continu-ousdegradationandre-polymerisation,andtoabioticprocesses,as

precipitationphenomena,atmosphericdrydepositionorleaching

ofwater-solubleScompounds.Mineralisationandimmobilisation

ofSoccurconcurrently,andthereleaseorincorporationof

inor-ganicsulphateintosoilorganicmatteristhusanetresultofseveral

processes(Maynardetal.,1983;Ghanietal.,1993).Sulphurmay

beretainedinsoilviatwomajormechanisms:absorptiononthe

soilsolidphaseorincorporationintoorganicforms.Theretention

ofsulphateinsoilsbyabsorptiondependsonthenatureofthe

col-loidalsystem,pH,sulphateconcentrationandtheconcentrationof

otherionsinthesolution(HarwardandReisenauer,1966).Evenfor

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soilswithamarkedcapacitytoretainsulphate,thestrengthofthe

retentionisweak,asadsorbedsulphatecanberemovedbyrepeated

extractionwithwater(Chaoetal.,1962).ThusthefateofSreleased

frommicrobialdegradationoforganicmatterorfromfertiliseris

eithertobeleachedwhenthewatermovesverticaldownwardin

thesoilproﬁleorabsorbedbytheplant.

Leachingis potentially one of themost important

contribu-tors toSdepletion.Sulphuris leachedboth as sulphateand as

dissolvedorganicsulphur(DOS),butthelatterismuchless

abun-dantinleachatethantheformer(Arowoloetal.,1994;Zhaoand

McGrath,1994).Overathree-yearperiod,Rileyetal.(2002)

esti-matedthatDOSaccountedfor6±10%ofthetotalSlosttodrainage.

Estimatesofsulphateleachingbylysimetersandrivercatchments

generallyrangesfrom1to60kgSha−1y−1 (Eriksenetal.,1998;

Eriksen,2009), butalso higherﬁguresof 100kgSha−1y−1 have

beenreported(GuzysandAksomaitiene,2005).

Agriculturalmanagementcancauseconsiderablevariationsin

sulphateleaching.TominimisetherisksoflargeSleachinglosses

fromwheatcropthepatternofSdistributionneedstobeoptimised

inrelationtocropSdemand(Korentajeretal.,1984;Eriksenand

Askegaard,2000;Rileyetal.,2002).Thisisaccomplishedbymaking

SavailablejustpriortoorsynchronisedwithcropSuptake,whileS

mineralisationduringtimeperiodsoflowornocropuptakeshould

beminimised(Eriksenetal.,2002).OptimisationofSreleasefrom

decomposingsoilorganicmatterandSfertiliserrelatedtoplantS

uptakeisacentralissueandgoalinappliedresearchconcerningSin

agriculturalsystems,andalsointhispaper.Thepresentworkwas

thereforeundertakentodetermineSandNleachingandSfertiliser

responsefromdurumwheatcrop.TheeffectsofdifferentratesofN

andSfertilisers,soiltypesandsplitapplicationsofSwere

investi-gated.Sulphurinputandoutputbalancesweredeterminedinorder

toevaluatethelong-termpossibilityofanadequateSsupplyforthe

wheatcrop.

2. Materialandmethods

Twoexperimentswereconductedwithdurumwheat(Triticum

durumDesf.)intwosuccessivegrowingseasons,2003–2004and

2004–2005, at the experimental station of the Department of

AgronomyandAgroecosystemManagementoftheUniversityof

Pisa,Italy, thatis locatedat adistance ofapproximately10km

fromthesea(43◦40N,10◦19E)and1mabovesealevel.The

cli-mateoftheexperimentalsiteiscold,humidMediterraneanwith

meanannualmaximumandminimumdailyairtemperaturesof

20.2 and9.5◦C,respectively, andprecipitationof 971mm, with

688mmreceivedduringtheperiodofdurumwheatcultivation,

thatisfromNovemberthroughJuly(Moonenetal.,2001).

Bothexperimentswereconductedwiththreereplications in

randomisedcompleteblockdesignsutilisinganopen-airlysimeter

installation.Thisconsistedof thirty-sixlysimetersof 100-L

vol-ume(0.25-m2 _area_and _0.4-m_height),_arranged _in_two_rows _of

18,spaced15cmandembeddedinexpandedclaytosmoothdaily

ﬂuctuationsinsoiltemperature.Lysimeterswereﬁlledwithasoil

tampedtoaboutoriginalsoilbulkdensity,andwereattachedto

a5-cmrigidPVCdrainthatendedinacentralcollectionfacility.

Soilsamples(0–40cmdepth) werecollectedinDecember2003

andDecember2004beforewheatseedingforthedeterminationof

soilproperties(Table1).Sampleswereairdried,grounded,and

analysed fortexture (hydrometermethod),pH(saturated paste

method),organicmatter(WalkleyandBlackmethod),totalN

(Kjel-dahlmethod),availableP(Olsenmethod),availableK(ammonium

acetateextraction)andtotalS(drycombustionandinfrared

detec-tion,Schumacheretal.,1995).ThefertiliserSandNtreatments,

aswellastheP and Krates werecalculatedbased onthe

bal-anceapproach,whichisconsideredamorereliablemethodthan

traditionalsoilteststodetermineplantnutrientavailability(Zhao

etal.,1999).

Phosphorusandpotassiumwereappliedpreplantingastriple

mineralphosphateandpotassiumchlorideatarateof100kgha−1

P2O5andK2O.Theadditionsofnitrogenandsulphurfertilisersare

describedlaterforeachexperiment.

Twodurumwheatvarieties,CresoandSvevo,weresownata

rateof100viableseedspercontainer,correspondingto400viable

seedsperm2_,_in_rows_spaced₁₅_cm_apart_on₁₂_December₂₀₀₃_and

15December2005.Cresoisanoldvariety(releasedin1974)that

waswidelycultivatedinCentralItalyinthepast20yearsandisstill

inuse.Itischaracterisedbyamoderatebutconstantyield,medium

grainqualityandahighadaptabilitytodifferentenvironmental

conditions.Svevoisamorerecentvarietycharacterisedbytaller

size,higherproductivityandimprovedgrainquality.

Cropswereirrigatedwhennecessarytoavoidwaterstressthat

mayoccurinplantsgrownincontainers,especiallyduringgrain

ﬁlling.Inbothyears,noirrigationwasappliedbeforeanthesisand

twoirrigationswereappliedbetweenanthesisandmaturity,

utilis-ingamicroirrigationsystemuntilﬁeldcapacitywasreached.Weed

controlwasperformedthroughoutwheatcyclebyhandhoeing.

Leachatesfromeachlysimeterwerecollectedduringtheentire

researchperiodinbothyearsaftereachmajorrainfalleventina

20-LPVCtank.LeachatevolumesweremeasuredandtheirN NO3

andS SO4concentrationsweredeterminedwithaDionexion

cro-matographmodelDX-120.Theﬂow-weightedN NO3andS SO4

concentrationsforthewholeleachingperiodwerecalculatedby

summing up N NO3 and S SO4 mass collected in the period

dividedbythetotalleachatevolumecollectedintheperiod.N NO3

andS SO4concentrationsweredeterminedalsoinrainfalland

irri-gationwater.MeanN NO3concentrationwas2.4mgL−1inrainfall

and1.9mgL−1inirrigationwater.MeanS SO4concentrationwas

7.4mgL−1inrainfalland2.6mgL−1inirrigationwater.

Atphysiologicalmaturity(stage90ofthescaleofZadoksetal.

(1974)),plantsfromeachcontainerweremanuallycutatground

levelandwerepartitionedintoculms,leaves,chaffandgrain.Roots

wereseparatedfromthesoilbygentlywashingwithwateruntil

theyweretotally clean.For dry weightdetermination, samples

fromallplantpartswereovendriedat65◦Ctoconstantweight.

Meankerneldryweightwasalsomeasuredandnumberof

ker-nelsperunitareaandharvestindex(HI)werecalculated.Samples

ofeachplantpartwereanalysedfornitrogen(Kjeldahlmethod)

andsulphur(wetashingandinfrareddetectionmethod)

concen-trations;NandScontentswerecalculatedbymultiplyingNorS

concentrationbydryweight.

2.1. Experiment1–nitrogenandsulphurrates

Theresearchwascarriedoutinthe2003–2004wheatgrowing

season.ThevarietiesCresoandSvevoweregrownwithtwolevelsof

Napplication,low(120kgNha−1)andhigh(180kgNha−1),

here-afterreferredtoasN120andN180,respectively,andthreelevelsof

Sapplication,nil,high(60kgSha−1)andveryhigh(120kgSha−1),

hereafterreferredtoasS0,S60andS120,respectively.Nitrogen

wasappliedasurea. Therateof120kgNha−1 wassplittedinto

twoapplicationsof60kgNha−1,beforeseedingandatﬁrstnode

detectable(stage31–4April2004),thatof180kgNha−1was

split-tedintothreeapplicationsof60kgNha−1 beforeseeding,atﬁrst

nodedetectableand15daysafterthisstage(26May2004).Sulphur

wasappliedpreplantingasagriculturalgypsum(CaSO4·2H2O).The

soiltypewasloamaccordingtotheUSDAclassiﬁcation.

2.2. Experiment2– soiltypeandsplittingofsulphurfertilisation

Theresearchwascarriedoutinthe2004–2005wheatgrowing

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Table1

SoilpropertiesinExperiments1and2.

Parameter Unit Experiment1 Experiment2

Clay-loamsoil Sandy-loamsoil

Sand(2mm>Ø>0.05mm) % 48.6 38.9 64.9 Silt(0.05mm>Ø>0.002mm) % 33.6 28.7 24.0 Clay(Ø<0.002mm) % 17.8 32.4 11.1 pH 8.3 7.2 6.8 Organicmatter % 1.8 1.7 1.3 TotalN gkg−1 _0.9 _1.1 _0.8 AvailableP mgkg−1 5.4 5.2 0.8 AvailableK mgkg−1 68.7 80.2 16.5 TotalS gkg−1 _0.32 _0.34 _0.23

(sandy-loamandclay-loam,accordingtotheUSDAclassiﬁcation)

withthreesplittingsofSfertilisation:(i)completelybefore

seed-ing,(ii)splitted60kgSha−1preplantingand(iii)60kgSha−1atﬁrst

nodedetectable(2April2005)andsplitted34kgSha−1

preplant-ingand86kgSha−1atﬁrstnodedetectable,hereafterreferredtoas

S120–0,S60–60andS36–84,respectively.Sulphurwasappliedas

agriculturalgypsum(CaSO4·2H2O)atthetotalrateof120kgSha−1

foralltreatments.Nitrogenwasappliedattherateof180kgNha−1

and was splitted 60kgha−1 preplanting as ammonium nitrate,

60kgha−1atﬁrstnodedetectableand60kgha−115daysafterthis

stageasurea.

2.3. Dataanalysis

Statisticalanalysisofdatawasperformedseparatelyforthetwo

experiments.DataweretreatedbyANOVA;intheﬁrstexperiment

themaineffectsofvariety,Nrate,Srateandtheirinteractionswere

tested,inthesecondthemaineffectsofvariety,soiltype,splitting

ofSfertiliser,andtheirinteractionsweretested.Signiﬁcantly

dif-ferentmeanswereseparatedatthe0.05probabilitylevelbythe

leastsigniﬁcantdifferencetest(Steeletal.,1997).

3. Results

3.1. Experiment1–nitrogenandsulphurrates

3.1.1. Grainyieldandyieldcomponents

Grainyieldanditscomponentswerenotaffectedbythe

inter-actionsamongvarieties,NratesandSrates.GrainyieldofSvevo

was,onaverage,by17%higherthanthatofCreso(Table2).The

increasewasattributedtohighernumberofspikesperunitarea

(+21%),owingtoagreatertilleringrate,andnumberofkernelsper

spike(+30%).Conversely,meankernelweightofSvevowasby8%

lower.DryweightofallplantpartsexceptgrainwashigherinCreso

thaninSvevoand,consequently,harvestindexwaslowerinCreso

(resultsnotshown).

TheincreaseofNratefrom120to180kgNha−1increasedgrain

yieldby9%,owingtoanincreaseofthenumberofspikesperunit

area(13%).Moreover,theincreaseofNrateslightlyreducedmean

kernelweightanddidnotaffectthenumberofkernelsperspike

(Table2).TheincreaseofNratealsoincreasedplantdryweightby

12%,duetotheincreaseofallplantparts.

TheincreaseofSratefrom0to60and120kgSha−1

progres-sivelyincreasedgrainyield (by5.4%fromS0toS120),and dry

weightofculms(6.6%)andofroots(12.5%)(Table2).Highergrain

yieldwassolelyduetotheincreaseofthenumberofkernelsper

spike.

3.1.2. Sulphurconcentrationandcontent

Sulphurconcentrationinallplantpartswashigheratthehighest

NandSfertiliserrates,buttheeffectwasstatisticallysigniﬁcant

onlyingrainandroots.Sulphurconcentrationingrainincreased

from1.2ofthecontrolto1.5gkg−1ofthehighestNandSfertiliser

rates.TheinteractionbetweenNrateandSratewassigniﬁcant

onlyforScontentofroots.AtthelowerNfertiliserrate,thehighest

levelofSincreasedby7%Scontentinrootscomparedtounfertilised

control,whileatthehigherNratetheincreaseduetoSfertiliserwas

by25%(Fig.1).Averagedoverfertilisersrates,CresogavehigherS

contentingrainandlowerinleavesandculms,comparedtoSvevo

(Table3).

The increase of N fertiliser increased S content of all plant

parts, therate of increase ranged from18% in roots to 40% in

leaves(Table3).Conversely,theincreaseofSfertiliser

progres-sivelyincreasedonlytheScontentofgrainandculms,respectively

by28and23%.Allsummarised,theuptakeofSbythewholeplant

wasby9.1kgha−1greateratN180thanatN120andby7.1kgha−1

greateratS120,comparedtoS0.

3.1.3. Nitrogenconcentrationandcontent

TreatmentsdidnotaffectsigniﬁcantlyNconcentrationthatwas,

onaverage,20.1,7.6,3.1,7.1and8.8gkg−1respectivelyingrain,

leaves,culms,chaffandroots.Conversely,nitrogencontentofall

Table2

Experiment1–dryweightofgrain,leaves,culms,chaff,rootsandyieldcomponents.Variety,nitrogenrateandsulphurratemeaneffects.

Treatments Grain Leaves Culms Chaff Roots Spikenumber Kernelnumber Meankernelwt.

(tha−1₎ _(n_m−2₎ _(n_spike−1₎ _(mg) Variety Svevo 5.5a 1.0a 5.5a 1.7a 1.6a 470.3a 25.3a 46.3a Creso 4.7b 1.2b 6.3b 1.8b 1.9b 389.7b 23.5b 51.4b Nitrogenrate N120 4.9a 1.0a 5.6a 1.7 1.6a 404.3a 24.5a 49.3a N180 5.3b 1.2b 6.2b 1.9 1.9b 455.7b 24.3a 48.4b Sulphurrate S0 4.9a 1.1a 5.7a 1.8a 1.6a 432.0a 23.8a 48.4a S60 5.1ab 1.1a 6.0ab 1.8a 1.7ab 431.5a 24.4ab 49.1a S120 5.2b 1.1a 6.1b 1.8a 1.9b 426.5a 25.0b 49.1a

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10 12 14 16 18 S0 S60 S120 Root N content (kg ha -1) Sulphur rate N120 N180 LSD p<0.05 12 14 16 18 20 S0 S60 S120 Root S content (kg ha -1) Sulphur rate N120 N180 LSD p<0.05

A B

Fig.1.Experiment1– nitrogen(A)andsulphur(B)contentofrootsasaffectedbynitrogenratexsulphurrateinteraction.

Table3

Experiment1–sulphurcontentofgrain,leavesandculms.Variety,nitrogenrate andsulphurratemeaneffects.

Treatments Grain Leaves Culms

(kgha−1) Variety Svevo 8.1a 1.5a 13.2a Creso 5.8b 2.0b 14.9b Nitrogenrate N120 6.0a 1.4a 12.1a N180 8.0b 2.0b 15.9b Sulphurrate S0 6.1a 1.6a 12.6a S60 7.0ab 1.8a 14.0ab S120 7.8b 1.8a 15.4b

Withintreatmentsvariety,NrateandSrate,numbersfollowedbythesameletter arenotsigniﬁcantlydifferentatP<0.05.

plantpartsexceptchaffvariedbetweenvarietiesandwasaffected

byNandSrates.GrainNcontentofSvevowasby28%higherthan

thatofCreso,whichhadinsteadhigherNcontentinleaves(+15%),

culms(+15%)and roots(+25%)(resultsnotshown).Asa

conse-quence,Nharvestindexwasby11%higherinSvevocomparedto

Creso.TheuptakeofNwiththehigherNratewas186kgha−1in

Svevoand166kgha−1inCreso.

AtthelowerNfertiliserrate,thehighestlevelofSincreasedby

33%Ncontentinrootscomparedtounfertilisedcontrol,whileat

thehigherNratetheincreaseduetoSfertiliserwasby10%(Fig.1).

BothNandSfertilisersincreasednitrogencontentingrain,leaves

andculms.Asaconsequence,theuptakeofNofthewholeplant

wasby39kgha−1greateratN180and18kgha−1greateratS120,

comparedtothelowerfertiliserrates(resultsnotshown).

3.1.4. Sulphurleaching

No signiﬁcant differences were observed in drainage water

amonganyofthetreatmentstested.Drainagewaterwasroughly

correlatedtorainfall,beinghigherinJanuary,FebruaryandApril

when thehighestrainfalls occurred. Rainfall during2003–2004

wheatgrowingseasonwasclosetonormalvaluesforthesite.

Sul-phurconcentrationindrainagewaterandleachedSwereaffected

onlybySfertilisation.IntheperiodfromJanuarytoApril,S

concen-trationwashigherthan16mgL−1andincreasedwiththeincrease

ofSrate(Fig.2).ThehighestSconcentrationsfromtheSfertilised

treatmentsoccurredinMarch,whilefromunfertilisedtreatmentit

occurredearlier,inFebruary.InMarch,a2-foldhigherS

concen-trationwasrecordedinleachatesfromSfertilisedsoilscompared

tounfertilisedone.

ThequantityofSlosttothedrainagewaterfromSfertilisedand

controltreatmentswashighestinJanuaryandFebruary.Sulphur

leacheduptoAprilincreasedwiththeincreaseofSrate,whilein

MayvalueswerelowandunaffectedbySfertiliser.Overthewheat

cycle,SleachedfromS60andS120wasby13and19kgha−1higher

respectivelythanfromtheunfertilisedcrop(Fig.2).

3.1.5. Nitrogenleaching

NosigniﬁcantdifferenceswereobservedinNconcentrationin

drainageand Nleaching betweenanyof thetreatmentstested.

Nitrogenconcentrationinwaterwashigherfollowingseeding,in

JanuaryandFebruary,anddecreasedthereaftertominimalvalues

inMay(Fig.2).Averagedoveralltreatments,totalamountofNlost

duringwheatcyclewas26kgha−1,almostentirelyaccountedforby

NleachinginJanuaryandFebruary(39%and43%respectivelyofthe

totalleachedN).FollowingMarch,leachinglosseswerenegligible.

3.1.6. Sulphurbalance

Averagedovervarieties,Soutputfromsoil(leachingplusplant

uptake) was similar for all treatments and increased with the

increaseofSfertiliserrate.Sulphurbalance,calculatedasthe

dif-ferencebetweenestimatedinputs(Sfertiliserandwetdeposition)

andoutputs,wasseriouslynegativefromunfertilisedcrop,only

slightlynegativefromS60andpositivefromS120(Table4).

Dif-ferencesbetweentreatmentswereduetotheincreaseofplantS

uptakeduetohigherSfertiliser.Tohavebalancedinputsand

out-puts,aSfertiliserratelowerthan120kgSha−1 buthigherthan

60kgSha−1shouldbeapplied.

3.2. Experiment2– soiltypeandsplittingofsulphurfertilisation

3.2.1. Yieldandyieldcomponents

Grainyieldanditscomponentswerenotaffectedbythe

inter-actionsamongvarieties,NratesandSrates.GrainyieldofSvevo

wasonaverageby12%higherthanthatofCreso,owingtoahigher

meankernelweight(Table5).Conversely,dryweightofleavesand

culmswere,respectively,13%and15%higherinCresothanSvevo.

Finally,harvestindexwas14%lowerinCreso(resultsnotshown).

Soiltypegreatlyaffectedcropproduction.Grainyieldofplants

growninclayloamsoilwas43%higher,anddryweightofleaves

andculmswererespectively43and44%highercomparedtoplants

growninsandyloamsoil(Table5).Rootdryweightwasunchanged

betweenthetwosoiltypes.Theincreaseofgrainyieldbetween

clayloamandsandyloamsoilwasduetohighernumberofspikes

perunitarea(+6%),numberofkernelsperspike(+10%)andmean

kernelweight(+20%).Thedifferencesofmeankernelweightarenot

causedbyvariationsofwateravailability,ascropswereirrigated

duringgrainﬁlling.

Conversely,Ssplittinghadscarceeffectondryweightofallplant

parts:thetreatmentS60–60increasedslightlygrainandrootsdry

weight(Table5).Thehighergrainyieldwasduetotheincrease

ofthenumberofspikesperunitarea.ThetreatmentsS120–0or

S60–60gavesimilargrainyield,buttheformerhadhighernumber

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Fig.2. Experiment1–sulphur(A)andnitrogen(B)concentrationindrainage,sulphur(C)andnitrogen(D)leachingduringwheatcycleasaffectedbysulphurratemean effect.InﬁguresCandD,valuesinboxesindicatetotalSleachingandtotalNleaching,respectively.Verticalbarsindicatestandarderror.

3.2.2. Sulphurconcentrationandcontent

Sulphurconcentrationinallplantpartswasaffectedonlybysoil

type,asvalueswerealwayshigherforplantsgrowninclayloam

soil,comparedtosandyloamsoil.Theincreaserangedfrom30to

35%inaerialplantpartsandwas42%inroots(resultsnotshown).

ThedifferencesbetweenvarietiesinScontentofallplantparts

weresimilartothoseobservedindryweight:Svevoshowedhigher

Scontentingrainandlowerinleaves,culmsandroots(Table6).

TheplantuptakeofSwas30.8kgha−1forSvevoand33.5kgha−1

forCreso,accountedformainlybyvegetativeplantpart,whilegrain

accountedforonly27%inSvevoand22%inCreso.

SoiltypegreatlyaffectedScontentofplants.Plantsgrownin

clayloamsoilhadhigherScontentinallplantpartsexceptchaff,

comparedtosandyloamsoil.Theincreasewas90%forgrainand

leaves,100%forculmsandnearly50%forroots(Table6).

SulphurcontentinallplantpartswasaffectedbySsplitting,

decreasingin thefollowing order:S60–60, S34–84and S120–0

(Table6).ThetreatmentS60–60increasedSuptakeofthewhole

Table4

Experiment1–sulphurbalance(inputsminusoutputs)basedonaverageofvarieties(kgSha−1₎_with_SE_in_brackets.

Treatments Inputs Outputs

Nitrogenrate Sulphurrate Wetdepositiona _S_fertiliser _Leaching _Plant_uptake _Balance

N120 S0 14.5 0.0 30.6 34.0 −50.1(3.4) S60 14.5 60.0 42.8 37.6 −6.0(1.9) S120 14.5 120.0 49.1 39.8 45.6(3.1) N180 S0 14.5 0.0 31.2 42.0 −58.7(4.2) S60 14.5 60.0 45.5 46.1 −17.1(3.0) S120 14.5 120.0 49.7 50.6 34.1(3.5)

a_Wet_deposition_of_S_was_calculated_from_the_volume_of_the_{precipitation}_and_the_{concentration}_of_S_in_the_{precipitation.}

Table5

Experiment2–dryweightofgrain,leaves,culms,chaff,rootsandyieldcomponents.Variety,soiltypeandsulphursplittingmeaneffects.

Treatments Grain Leaves Culms Chaff Roots Spikenumber Kernelnumber Meankernelwt.

(tha−1₎ _(n_m−2₎ _(n_spike−1₎ _(mg) Variety Svevo 5.5a 1.0a 4.6a 1.2a 1.5a 513.8a 23.7a 45.1a Creso 4.9b 1.2a 5.4b 1.2a 1.6a 523.9a 23.1a 40.8b Soiltype Clayloam 6.1a 1.3a 6.0a 1.2a 1.6a 534.4a 24.5a 46.9a Sandyloam 4.3b 0.9b 4.0b 1.2a 1.5a 503.3a 22.3b 39.0b Ssplitting S120–0 5.2a 1.1a 4.9a 1.2a 1.4a 510.1a 25.2a 39.8a S60–60 5.3b 1.1a 5.1a 1.2a 1.7b 535.6b 24.3a 40.6a S36–84 5.1a 1.1a 4.9a 1.2a 1.5ab 510.8a 20.7b 48.3b

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Table6

Experiment2–sulphurcontentofgrain,leaves,culms,androots.Variety,soiltype andsulphursplittingmeaneffects.

Treatments Grain Leaves Culms Roots

(kgha−1₎ Variety Svevo 8.4a 1.7a 8.4a 10.4a Creso 7.4b 1.9a 10.3b 12.0b Soiltype Clayloam 10.3a 2.3a 12.5a 13.4a Sandyloam 5.5b 1.2b 6.2b 9.1b Ssplitting S120 6.9a 1.6a 8.9a 9.6a S60–60 9.0b 1.8a 9.9b 12.3b S36–84 7.8ab 1.9a 9.2ab 11.8b

Withintreatmentsvariety,soiltypeandsulphursplitting,numbersfollowedbythe sameletterarenotsigniﬁcantlydifferentatP<0.05.

Table7

Experiment2–nitrogencontentofgrain,leaves,culmsandroots.Variety,soiltype andsulphursplittingmeaneffects.

Treatments Grain Leaves Culms Roots

(kgha−1₎ Variety Svevo 121.1a 10.7a 14.7a 12.7a Creso 104.7b 12.9b 20.0b 14.5b Soiltype Clayloam 136.1a 14.2a 20.9a 14.5a Sandyloam 89.7b 9.4b 13.7b 12.7b Ssplitting S120–0 108.5a 11.0a 17.1a 11.5a S60–60 118.7b 12.1a 17.5a 15.3b S36–84 111.5a 12.3a 17.4a 14.0b

Withintreatmentsvariety,soiltypeandsulphursplitting,numbersfollowedbythe sameletterarenotsigniﬁcantlydifferentatP<0.05.

plantby2.4kgha−1respecttoS36–84andby6.2kgha−1respect

toS120–0.

3.2.3. Nitrogenconcentrationandcontent

Nitrogenconcentrationinallplantpartswasnotmodiﬁedby

treatments.GrainNcontentwas16%higherinSvevothanCreso,

whileleaves,culmsandrootswere20,36and15%lower,

respec-tively.Atawhole,Nplantuptakewasonly4%lowerinCreso.

PlantsgrowninclayloamsoilhadNcontentingrain,leavesand

culmsby52%higherandNcontentinrootsby14%highercompared

toplantsgrowninsandysoil(Table7).

The splitting of S application preplanting and after seeding

(S60–60)increasedNcontentofgrain,leaves,culmsandroots

com-paredtotheothertwoapplications,althoughonlythedifferences

ingrainNcontentwerestatisticallysigniﬁcant.Allsummarised,N

uptakebyplantsrangedfrom157kgha−1ofS120–0to173kgha−1

ofS60–60(resultsnotshown).

3.2.4. Sulphurleaching

Theamountofdrainagewaterandsulphurleachingincreased

duringwinterastherainfallincreased.Rainfallduring2004–2005

wheatgrowingseasonwaslowerthannormal,withatotalamount

only55%ofthe100-yearmeanofthesite.SoiltypeandSsplitting

affectedsulphurconcentrationindrainagewaterandSleaching.

TheconcentrationofSindrainagefromclayloamsoilwasalways

higherthantheonefromsandyloamsoilatallSsplittings,but

differences decreased throughout the wheatcycle (Fig. 3).The

decreaseofSfertiliserappliedpreplantingreducedby15–37%S

concentrationinthedrainagescollectedinJanuary,Februaryand

March(Fig.3).Consequently,Slossesfromclayloamsoil were

higherthantheonesfromsandyloamsoilanddecreasedwhen

theapplicationofSfertiliserbeforeseedingwasreduced.

Overthewholewheatcycle,Sleachingwasaffectedbythe

inter-actionbetweensoiltypeandSsplitting.ThequantitiesofSlostfrom

clayloamsoilwereconsistentlyhigherthantheonesfromsandy

loamsoil,butSsplittingreducedlosseslessinsandyloamsoilthan

inclayloamsoil(Fig.3).

3.2.5. Nitrogenleaching

Drainage, N concentration in drainage and leached N were

affectedonlybysoiltype.DrainagefromsandyloamsoilinJanuary

andMarchwas56and52m3_ha−1_greater,_{respectively,}_than_the

onefromclayloamsoil,whiledrainageinFebruaryandAprilwere

similarinthetwosoiltypes(Fig.4).

TheconcentrationsofNindrainagefrombothsoiltypesvaried

duringwheatcycleandwerehigherinFebruary.Valuesfromclay

loamsoilwereconsistentlyhigherthansandyloamsoilinJanuary

andFebruary,whilein thelater drainagesvalues werelowand

similarbetweensoils(Fig.4).Similarly,thequantityofNleaching

fromclayloamsoilwashigherthansandyloamsoilinJanuaryand

February,whileinMarchandAprilNleachingwasverylowfor

bothsoils(Fig.4).Overthewheatcycle,32kgNha−1werelostby

leachingfromclayloamsoiland21kgNha−1werelostfromsandy

loamsoil.

3.2.6. Sulphurbalance

Averagedovervarieties,Sleachingaccountedfor40–53%ofthe

totaloutputfromsoil(leachingplusplantuptake)(Table8).The

inputandoutputbalancewaspositiveforalltreatments,showing

asurplusofSinsoilrangingfrom51to85kgha−1(Table8).The

surpluswasnotsubstantiallymodiﬁedbySsplittingandwasmore

stronglyaffectedbysoiltype:averagedovervarietiesandSsplitting

rates,thesurplusofSfromsandyloamsoilwasby50%higher.

Fig.3.Experiment2– sulphurconcentration(A)indrainageandsulphurleaching(B)duringwheatcyclefromclayloamsoil(opensymbols)andsandyloamsoil(closed symbols)asaffectedbysulphursplitting.InﬁgureB,valuesinboxindicatetotalSleaching.Verticalbarsindicatestandarderror.

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Table8

Experiment2–sulphurbalance(inputsminusoutputs)basedonaverageofvarieties(kgSha−1₎_with_SE_in_brackets.

Treatments Inputs Outputs Balance

Soiltype Ssplitting Wetdepositiona _S_fertiliser _Leaching _Plant_uptake

Clay-loam S120–0 9.4 120.0 38.5 37.0 53.9(4.2) S60–60 9.4 120.0 33.7 44.6 51.1(4.9) S36–84 9.4 120.0 26.8 40.3 62.3(5.7) Sandy-loam S120–0 9.4 120.0 23.7 20.6 85.1(7.4) S60–60 9.4 120.0 23.1 25.5 80.8(6.3) S36–84 9.4 120.0 19.3 25.0 85.1(6.6)

a_Wet_deposition_of_S_was_calculated_from_the_volume_of_the_{precipitation}_and_the_{concentration}_of_S_in_the_{precipitation.}

0 10 20 30 40 50 60

Jan Feb Mar Apr

N concentration

(mg L

-1

)

B

0 5 10 15 20 25

Jan Feb Mar Apr

N leaching

(kg

ha

-1

)

C

0 100 200 300 400 500

Jan Feb Mar Apr

Drainage water (m

3

ha

-1

)

Clayloam soil

Sandy loam soil

A

0 10 20 30 40 Clay loam soil Sandy loam soil

Fig.4.Experiment2–drainagewater(A),nitrogenconcentrationindrainage(B) andnitrogenleaching(C)duringwheatcycleasaffectedbysoiltypemeaneffect. InﬁgureC,valuesinboxindicatetotalNleaching.Verticalbarsindicatestandard error.

4. Discussion

4.1. ResponsestoNfertiliser

Nitrogenfertiliserincreasedgrainyieldanddryweightofall

plantpartsexceptchaffofbothvarieties.Thisresponsewassimilar

tothatreportedbyErcolietal.(2011)intheﬁeldunderthesame

environmentalconditionsandapplyingthesameNrates,though

plantsgrown inlysimetersgave higher yield,probablybecause

theywereexposedtomorefavourableconditions.Resultsofthis

researchindicatethatcropfertilisedwith120kgNha−1 hadless

thanoptimalsoilNavailabilityforgrowth.TheriseofNratedid

notaffectNconcentrationofallplantparts,buttheirNcontent

wasincreasedowingtotheeffectondryweight.Nitrogenfertiliser

didnotaffectSconcentrationinallplantpartsandconsequently

variationsintheirScontentswereduetovariationsindrymatter

promptedbyNrate.

DifferencesbetweenvarietiesinthecapacitytoaccumulateN

ingrainwerenotevidentinthistrial:Svevohadhighergrainyield

andNandSuptakebuttheresponsetofertilisertreatmentswas

similarforbothvarieties.

AsexpectedinMediterraneanenvironments,whererainfallis

concentratedinautumnandwinterwhenplantNuptakeislow,

inourexperimentleachinglossesofNoccurredmainlyinJanuary

andFebruary,whichaccountedforover90%ofthetotalleaching

loss.Thiswastobeexpectedsincethedifferentiationbetweenthe

twoNtreatmentsoccurredlateinMarch,whenrainfallandthe

consequentdrainagevolumewerelow.Itisworthnotingthatin

Aprildrainagevolumewashigh,butNconcentrationwasverylow,

probablyasaconsequenceofhighplantuptake.Thus,thetimingof

NdistributioniscrucialtominimiseNleachinglosses.Thebeneﬁts

obtainedwiththehigherNratereliedonthefulﬁllmentofcrop

requirementscoupledwithminimisedNlosses.

4.2. ResponsestoSfertiliserrate

Sulphurapplicationincreaseddry weightand Suptakeofall

plantpartsexceptchaff,butonlygrainandrootshadhigherS

con-centrationathigherSrate.Grainyieldincreasewasmainlydueto

anincreaseofthenumberofkernelsperspike,whichwas

inter-pretedasastimulationoftheinitiationofspikeletsand/orﬂorets,

ortoareductionofﬂoretmortality(Archer,1974;Monaghanetal.,

1997;Ercolietal.,2011).

SulphurfertiliseralsoincreasedNcontentofgrain,culmsand

roots.AtlowNavailability,sulphurfertilisationstimulatedN

accu-mulationinroots.Theresponseofallplantparts,exceptroots,toN

andSfertiliseragreewithourpreviousresearch,wherewecould

notdemonstrateanysynergismbetweenNandSrate,whichdoes

notsupportthehypothesisofZhaoetal.(1999)andFlæteetal.

(2005),assertingthatcropresponsetoSfertilisationdependson

theamountofNfertiliser,andthatSdeﬁciencymaybeinduced

byahighamountofNsupply.Probably,inourexperimentplants

fertilisedwith180kgNha−1werenotdriventoSdeﬁciency.

ThepositiveeffectofSapplicationondrymatterandSuptake

wasdetectedalreadyatS60andnofurthersigniﬁcanteffectwas

evidencedwiththehigherrate.Thus,wecanassumethatS60is

notlimitinginourenvironment.Ourpreviousresearch,carriedout

inthesameenvironmentintheﬁeld,foundthatSconcentrationin

grainincreasedandgrainqualitywasimprovedwhenSapplication

wentbeyondthemaximumgrainyield,whichprobablyindicates

aluxuryconsumption(Ercolietal.,2011).

Averagedovertheseasons2003–2004and2004–2005,S

leach-ing duringthe wholewheatcycle was35kgSha−1,which was

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leachingintheperiodMarch–Aprilaccountedfor24–45%ofthe

totalamountofSleachedduringwheatcycle.Thus,inour

envi-ronment,theriskofhighSlossesbyleachingishighespeciallyin

spring,duetothelowSuptakebytheplantsandthehighrelease

ofSbythedecomposingorganicmatterinsoil.Sulphurfertiliser

rateincreasedSconcentrationindrainagewaterandconsequently

Sleachedduringwheatcycle.Comparedtounfertilisedcontrol,S

leachedwasby13kgha−1higheratS60andby19kgha−1higher

atS120.

4.3. ResponsestoSfertilisersplitting

Inﬁeldconditions,sulphurnutritionofwheatmayberestricted

astheSavailabilityinsoilisnotnecessarilysynchronisedwithplant

needsandtheredistributionofSfromvegetativetissuestograin

isconsiderablylessthanforN(Monaghanetal.,1999).Hocking

(1994)foundthatonlyabout33%oftheSinstemandleaveswas

redistributedtothegrain,comparedtoapproximately75%forN.

ThisimpliesthattheSavailabilityneedstobemaintainedat

suf-ﬁcientlevelsthroughout thewholeperiod ofgrowthtoachieve

adequateaccumulationofSinthegrain(Flæteetal.,2005).

Inourresearch,Savailabilityduringcropcycleaffectedthe

ini-tiationanddevelopmentofplantorgansandhencegrainandyield

components.Thesplittingofsulphurfertiliserduringcropcycle

modiﬁedgrainyield.Thehighestgrainyieldwasobtainedwiththe

applicationof60kgSha−1beforeseedingand60kgSha−1atstem

elongation.TheapplicationofSentirelybeforeseedingor

split-ted36kgSha−1beforeseedingand84kgSha−1atstemelongation

gavesimilaryields,butvalueswereobtainedwithdifferent

con-tributionsofyieldcomponents:higherkernelnumberperspike

fortheformerandhighermeankernelweightforthelatter.Thus,a

higherSavailabilityatseedingpromotedthedevelopmentof

spike-bearingculmsandthespikesize,whilethehigheravailabilityatthe

beginningofstemelongationfavouredtheaccumulationof

assim-ilatesintograin.SulphursplittingalsoincreasedNandSuptake

ofplants:thehighestNandSuptakewererecordedwith

applica-tionofS60–60.TheeffectofthesplittingofSfertiliserwassimilar

forbothvarieties,asexpected,andalsoforsoiltypes,asno

inter-actionwasdetectedforanyofthemeasuredcharacters.Thuswe

canconcludethatthetimingofSapplicationdidnotmodifythe

mineralisationandimmobilisationpatternofsulphurinsoil,and

thevariationsduringwheatcycleofSapplicationratewere

prob-ablynothighenoughtogiverisetodifferencesinSavailabilityby

modiﬁcationsofthemobilisation/immobilisationbalance.

SulphursplittingmodiﬁedalsothequantitiesofSlostby

leach-ing: Sapplicationlater duringwheat cyclereduced Slossesby

leachingandtheeffectwashigherinclayloamsoil,which

con-ﬁrmsitshigherretentioncapacityofS.However,sulphateleaching

thatoccurredwhenSwasappliedbeforeseedingisnotexpected

tohaveadetrimentalenvironmentalimpact,sincethepeakS

con-centration(50.8mgL−1inMarch)waswellbelowtheEClimitof

83mgSL−1indrinkingwater(directive98/83/EC).Thusthe

ben-eﬁtsfromSsplittingrelyonlyontheincreaseofsulphurfertiliser

useefﬁciency.

Plantdryweightand Suptakewerealsohigherinclayloam

soilthan in sandysoil, as soilswitha higher claycontent and

thushigherstoragecapacityforwaterhaveahigherproduction

potentialandconsequentlySremovalof cropsgrownincreases

withrisingclaycontent(Pedersenetal.,1998).Lighttexturedsoils

aregenerally believed tobemostat riskof Sleachingbecause

oftheeasewithwhichtheleachatemovesthroughthesoiland

alsobecausesuchsoilshavelowabsorptioncapacities(Walkerand

Gregg,1975;McGrathandZhao,1995).Conversely,inourresearch

higherSlossesoccurredfromclayloamsoilcomparedtosandy

loamsoil.WorkofEriksenetal.(1995)indicatedgreatdifferences

innetmineralisationofSamongdifferentsoilsandsuggestedthat

mineralisedSwasnotsigniﬁcantlycorrelatedwithtotalorganicS

contentsofthesoilbutwithmicrobialactivity.

4.4. Sulphurbalance

Severalstudieshaveshowntheimportanceofavailabilityofsoil

SduringcropgrowthandtheneedtoapplyadditionalSfertilisers

toavoidSdeﬁciencysymptoms(CurtinandSyers,1990;Guzysand

Aksomaitiene,2005).IndurumwheatSnutritionisalsocrucialto

improvegrainquality(Lerneretal.,2006;Ercolietal.,2011).Amass

balanceapproachfordeterminingtheSfertiliserrateshouldbe

appliedinordertoreduceenvironmentallossesofSanddepletion

ofSinsoil(Eriksenetal.,1995).

Inourresearch,anequilibriumbetweenSinputandoutputwas

notreached,astheoverallSbalancegreatlydifferedinthetwo

experiments,beinghighlypositiveorseriouslynegative.TheS

bal-ancewaspositiveinbothexperimentsonlywhenthehigherSrate

wasapplied,asmoreSwasimportedthanremoved.Thus,no

sub-stantialSdeﬁcitmaybeexpectedinshortterm,providedthathigh

SfertiliserrateisappliedandtheavailabilityofSissynchronised

withplantneeds.

Previousstudies havereportednoeffectofSfertilisationon

mineralisation–immobilisationprocesses(Wuetal.,1995;Knights

etal.,2001)orreducedimmobilisationandgrossmineralisation

(Nziguhebaetal.,2005).Ourstudyshowedthatintheunfertilised

plotsnetmineralisationofsoilorganicSmusthavecontributed

substantiallytobothleachingandplantuptakeofS,whileinthe

fertilisedplotsbothdeﬁcitandsurpluswereevidenced,suggesting

eitheradepletionofsoilorganicSreservesoranimmobilisation

offertiliserS.HowevertoshowmoreexplicitlyhowtheSbalance

andavailabilityinsoilareaffectedbySfertilisationinour

environ-ment,long-termdataobtainedwithradioactivetracersshouldbe

considered.

5. Conclusions

TheseresultsindicatethatinMediterraneanregionswithhigh

winterrainfallsigniﬁcantleachinglossesofSarelikelytooccur

insoilswithhighorganicScontent.BecauseSisreadilyleached,

Sapplicationsshouldbetimedtocoincidewiththephaseofhigh

demandbycrops,whichusuallymeansinlatespringratherthan

inautumn,andmanagementoptionsgenerallyemployedfor

min-imising nitrateleaching shouldalso be applied to Sfertilisers.

Moreover,it seemsclearthatifcropyieldand qualityaretobe

maintainedatpresentlevels,plantSuptakeandSleachingmust,at

leastinpart,bereplacedbySfertilisationbecauseSmineralisation

cannotfulﬁlltheSdemandofthewheatcrop.

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