Impact of organic no till vegetables sys

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ContentslistsavailableatScienceDirect

Scientia

Horticulturae

j o u r n a l ho 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 / s c i h o r t i

Impact

of

organic

no-till

vegetables

systems

on

soil

organic

matter

in

the

Atlantic

Forest

biome

A. Thomazini

a,∗

_,

_E.S.

_Mendonc¸

_a

a

_,

_J.L.

_Souza

b

_,

_I.M.

_Cardoso

c

_,

_M.L.

_Garbin

a a_Department_of_Plant_Production,_Federal_University_of_Espírito_Santo,_29500-000_Alegre,_ES,_Brazil

b_Research_of_{INCAPER—Centro}_Serrano,_BR-262,_km_94,_29.375-000_Venda_Nova_do_Imigrante,_ES,_Brazil

c_Soil_Science_Department,_Federal_University_of_Vic¸_osa,_Avenida_P.H._Rolfs,_s/n,_Vicosa_36570-000,_MG,_Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received25August2014 Receivedinrevisedform 25November2014 Accepted1December2014

Keywords:

Greenmanure

Labileandstablefractions Soilhealth

SoilCbalance

a

b

s

t

r

a

c

t

Soilorganicmatteriswidelyrecognizedasastrategyusedtoimprovesoilqualityandreducecarbon emissionstotheatmosphere.Afieldstudywascarriedouttoinvestigatetheeffectsofcovercropsin organicno-tillvegetablessystemsonchangesinsoilorganicmatterandCO2 Cemissions,indryand rainyseasons.WehypothesizedthatCO2 Cemissionsarehigherinconventionaltillascomparedwith no-till,andthatno-tillincreasessoilCsink.Thecroprotationcompriseda3-yearcroppingsequence involvingtwocropsperyear—cabbage(BrassicaoleraceaL.)inwinterandeggplant(Solanummelongena L.)insummertime.Treatmentswereno-tillondeadmulchofgrass(AvenastrigosaSchreb.andZeamays L.),leguminous(LupinusalbusL.andCrotalariajunceaL.),intercrop(grassandleguminous)and conven-tionaltill(nodeadmulch)withrotaryhoearrangedinarandomizedblockdesignonaclayeyOxisol(Typic Haplustox)atDomingosMartins-ES,Brazil.On2012and2013,disturbedsoilsamplesatthreedifferent layers(0–5,5–15and15–30cm)andundisturbedsamplesat0–10,10–20and20–30cm,forchemical andorganicmattercharacterizationweretaken.CO2 Cemissionsandsoiltemperatureweremeasured insituonMarch,May,AugustandOctober2012andFebruary2013(after3yearsofexperiment). Con-ventionaltillsiteshowedthelowestmicroporosityvaluesandthehighestmacroporosity,followedby lowersoilbulkdensityat0–10cmlayer.TotalorganicCrangedfrom34.94to50.48gkg−1_in_intercrop and27.11to43.74gkg−1_in_conventional_till._Total_N_ranged_from_2.81_to_5.34_g_kg−1_in_grass_and_2.54 to4.51gkg−1_in_conventional_till._Highest_C_stock_was_recorded_in_intercrop._Conventional_till_showed lowerlabileCvalueswhilerecalcitrantCwashigherintheintercroptreatment.Theannualaverageof CO2 Cemissions(␮molCO2m−2s−1)followedtheorder:grass(15.89)>intercrop(13.77)>leguminous (13.09)>conventionaltill(11.20).Highestannualaverageofsoiltemperaturewasrecordedin conven-tionaltill(23.95◦_C)._Lowest_annual_mean_of_soil_water_content,_microbial_biomass_C,_and_highest_metabolic

quotientwererecordedinconventionaltill.Theseresultssuggestthattheuseofcovercropsandorganic compostinpre-plantingpromoteCincrements.Thecontributionoforganicresiduesincreasesthewater holdingcapacityandreducessoiltemperature.No-tillreducessoildisturbanceandpromotesapositive balanceofC.Organicno-tillvegetablesystemsisastrategytoincreasesoilCandshouldbeencouraged inordertoincreasesoilqualityintheAtlanticForestBiomeinBrazil.

1. Introduction

TheBrazilianAtlanticForestisnowreducedtoabout11.4to16% ofitsoriginalcoverofapproximately150millionhectares(Ribeiro etal.,2009).Mostdeforestedareasarecomposedofagricultural

∗Correspondingauthor.Tel.:+552733593971;fax:+552835528927.

E-mailaddresses:andre.thz@gmail.com(A.Thomazini),

eduardo.mendonca@ufes.br(E.S.Mendonc¸a),jacimarsouza@yahoo.com.br

(J.L.Souza),irene@ufv.br(I.M.Cardoso),mlgarbin@gmail.com(M.L.Garbin).

systemsondegradedsoils.Anthropogenicactivitiesleadtoland misuse causingchangesinthephysical,chemicalandbiological attributesofsoils(Reicoskyetal.,1999;Powlsonetal.,2011).This impliesdecreasesinthestorageoforganiccarbonandnutrientsas wellasintheproductivecapacityofsoils,sinceCisanindicator usedtoassesssoilquality(SilvaandMendonc¸a,2007;Ghoshetal., 2012).

Itiswidelyrecognizedthatsoilorganicmatterisoneofthemost importantindicatorsofsoilqualityandhealth(Lal,2004;Ghosh etal.,2012).Increasingormaintainingsoilorganicmatteris criti-caltoachieveoptimumsoilfunctionsandcropproduction(Ghosh

http://dx.doi.org/10.1016/j.scienta.2014.12.002

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etal.,2012).Whenmonitoringsoilqualityinthetropics,sensitive soilqualityindicatorsneedtobeidentified,mainlyduethe contin-uousandintensivevegetableproductionintheseareas(Moeskops etal.,2012).Soilmanagementcanleadtohigherdecomposition ratesoforganicmatterdecreasingtheconcentrationofthissoil component(SilvaandMendonc¸a,2007).Agriculturecan signifi-cantlycontributetoelevateatmosphericCO2 concentrationsasa

consequenceofsoilmanagement(Powlsonetal.,2011).TheseC lossestotheatmospherecanbemainlyreducedbyminimizing soildisturbance,eitherwithno-tilloragroecologicalmanagement (SilvaandMendonc¸a,2007).Itisestimatedthat89%ofthepotential formitigationofgreenhousegasesproducedbyagriculturerelies onCsequestration(Smithetal.,2008).Inaddition,increasingthe soilorganicCcontentisanimportantstrategytodealwithclimate changesdrivenbyCemissionstotheatmospherefromagricultural lands.

No-tillandorganicagricultureincreasesoilCandN sequestra-tion,andreducetheoxidationofsoilorganicmatter(Bayeretal., 2009;Campigliaetal.,2014).Continuousinputofplantresidues andpaucityofsoildisturbancepromotereductionsinCO2 C

emis-sions through decreasesin organicmatter decomposition rates (Lal,2004;Bayeretal.,2009).Onotherhand,conventionalcrop production intensify soil disturbanceand, consequently, break-downthesoilaggregates(Bayeretal.,2009).Conventionaltillage isthemostcommonagriculturalmanagementforvegetable pro-ductioninareasformerlyoccupiedbytheAtlanticForestinBrazil. Inaddition,vegetableproductionishistoricallymanagedbyfamily smallholders.Intensivefarmingorintensivesoilpreparationin hor-ticulturedegradesthesoil–plantenvironment,mostlyduetothe reductioninconcentrationandqualityofsoilorganicmatterand thediversityofsoilorganisms(Tianetal.,2011).Degradationofsoil organicmatterleadstolong-termdecreasesinhorticultural pro-ductivity.Thus,sustainabletillageispreferabletoattainapositive netbalanceofCinthehighlyweatheredtropicalsoils(Mendonc¸a andRowell,1996).

Theuseofcovercropsrepresentapotentiallyvaluablesupply oforganicresidues(Csource) whentheyareused inno-tillage systemsandtheirresiduesareleftonthesoilsurface(Campiglia etal.,2014).No-tillsystemscanmitigateCO2 Cemissions.Thisis

becausecroprotationandorganicresiduesonsoilsurfacepromote gradualdecompositionoforganicmatter,favoringCincorporation (Bayeretal.,2009;Conceic¸ãoetal.,2013).Physicalprotectionof organicmatterprovidedbystableaggregatesunderno-tillreduce organicmattermineralizationandleadtoCaccumulation(Sixetal., 2004).However,thereisalackofinformationaboutCstoragegains and CO2 C soil emissionsby organicno-till vegetablesystems,

especiallyin theareasformerlyoccupiedbytheAtlanticForest biome,awell-knownbiodiversityhotspot(Myersetal.,2000).Here, wereporttheresultsofalongtermfieldexperimentconducted indryandrainyseasons.Weaimedtoinvestigatetheeffectsof covercrops inorganicno-till vegetablessystems onchangesof soilorganicmatterandCO2 Cemissions,indryandrainyseasons.

WehypothesizedthatCO2 Cemissionsarehigherinconventional

tillascomparedwithno-till,andthatno-tillincreasessoilCsink, leadingtoimprovedsoilquality.

2. Materialandmethods

2.1. Sitelocation,characterizationandlandusespriortothe experiment

The study was carried out at the 2.5ha organicagriculture experimentalsiteofIncaper(EspíritoSantoInstituteforResearch, TechnicalAssistanceandRuralExtension),municipalityof Domin-gosMartins-ES (20◦₂₂′_SE₄₁◦₀₃′_W)_altitude_of₉₅₀_m_above_the

Fig.1. Averagemonthlyprecipitationandairtemperatureofthemunicipalityof DomingosMartinsbetweenJanuary2012andFebruary2013.DatafromIncaper.

sea.TheclimateoftheregionisAw(tropicalclimateanddry sea-soninwinter),precipitationrangesfrom750to1500mmperyear, andallmonthsoftheyearhaveaveragetemperaturesof18◦_C_or higher.Theregionischaracterizedbydrywinterandrainysummer (Köppen,1923).Meanmonthlyprecipitationandairtemperature are presented in Fig.1. Soilis classified asRed-Yellow Latosol, BrazilianClassificationSystem(Embrapa,2006)orasclayeyOxisol, TypicHaplustox(SoilTaxonomy,USDAclassification).From1990to 2009,thisareawascultivatedwithorganicvegetables(mainly let-tuce,cabbageandeggplant).Organicmanagementwasperformed using15Mgha−1_of_organic_compost_(dry_mass)_amendments._The

composting areafollowed theindore system(Miller and Jones, 1995)withalternatinglayersstackedformingcellsthatreceived manualeversionperiodicallyinordertocontrolhumidity(50%) and temperature(60◦_C)._The _method_relies_on_aerobic _activity, althoughportionsofthepilecanbecomeanaerobicbetween turn-ings. Moreover, it provides better control of flies, more rapid and uniform decomposition rates and less problems regarding moisturecontrol(MillerandJones,1995).Thecompostwas pre-paredwithastackedmixtureof:groundedgreencamerongrass (PennisetumpurpureumSchumach.),coffeehusk,cropresiduesof maize and beans, and inoculation with chicken manure at the rate of 50kgm−3_. _Organic _compost _{characteristics} _were _(total

amount):52%organicmatter,16:1carbon:nitrogenratio,7.3pH,2% nitrogen,1.2%phosphorus,1.2%potassium,4.8%calcium,0.5% mag-nesium,54mgdm−3 _copper, ₁₈₈_mg_dm−3 _zinc,_12,424_mg_dm−3

iron,793mgdm−3_manganese,₂₅_mg_dm−3_boron._More_details_of

theorganicvegetablecropping(1990–2009)canbefoundinSouza etal.(2012).

2.2. Experimentaldesign,covercropsandcroprotation

Theorganicno-tillvegetablessystemsexperimentwasinitiated in 2009.Theexperiment comprisesfourtillagesystems, imple-mentedon4m×6mplots,accordingtoaRandomizedComplete BlockDesign,withsixreplicates(totalizing24permanent experi-mentalunits)coveringatotalareaof576m2_._Therefore,_the_effects

oforganicmanagementaccumulatedovertheyears.Tillage treat-mentsconsistedof:

(i)No-tillondeadmulchofgrass(grass):blackoat(Avenastrigosa Schreb)wasusedaswintercovercropfollowedbymaize(Zea maysL.)assummercovercrop.

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(iii) No-tillondeadmulchofgrass andleguminous (intercrop): grassandleguminousplantswereintercroppedusingthesame covercropsingrassandleguminoustreatments.

(iv)Conventional plow-based tillage (Conventionaltill): imple-mentedusingconventionaltillagewithrotaryhoeoneweek beforeplanting,withnocovercrop.Thetractorusedwasarear rotaryminitiller(YanmarMRT-650EX)withtherotarytines placedrightbehindthewheels.Thisisthemainvegetable crop-pingsystemoftheBrazilianhorticulture(Souzaetal.,2012).

Operationscheduleconductedannuallyintheno-tilland con-ventionaltillwerepresentedinTable1.From2009to2013,no-till wasperformedwithblack oatand whitelupinas wintercover crop, followed bycabbageaswinter vegetablecrop. Maizeand sunnhempworkedassummercovercrop,followedbyeggplantas summervegetablecrop.Blackoatandwhitelupinweresownon March2012aswintercovercrops.Covercropseedswerespread manuallyandlightlyburied.Covercropsweresowninrowsspaced 33cmfromeachotherforalltreatments.Theseedrateswere480g perplotforblackoatand660gperplotforwhitelupin.Inthe inter-croppedsamplingunits,seedswerereducedtohalfofthesevalues. OnJuly2012,covercropsweremowedbymechanicalmowingand cabbagewasplanted.Covercropresidueswereleftonthesoil sur-faceasorganicdeadmulchandtheywerenotincorporatedintothe soil.Onemontholdcabbageseedlingsweretransplantedbyhand. Thecabbageseedlingswerearrangedinsinglerowsdistant60cm fromeachother.Thedistancebetweenthecabbageplantsinthe rowswas40cm.

Afterwintercrop,maizeandsunnhempweresownonOctober 2012assummercovercrops.Theseedrateswere600gperplotfor maizeand300gperplotforsunnhemp.Residuesweremowedon February2013followedbyeggplant(Solanummelongena)planting. Eggplantseedlingsweregrownintubesof180cm3_,_using_a_mixture

oforganiccompost/soilof1:2assubstrate.Theeggplantseedlings werearrangedinsinglerowsatadistanceof120cmbetweenthem. Thedistancebetweenthecabbageplantsintherowswas70cm. Cabbageandeggplantreceived15Mgha−1_of_organic_compost_(dry

mass)atplantinginallno-tilltreatments.Cabbageandeggplant seedlingswereirrigatedimmediatelyaftertransplantinginorder toavoidmoisturestress.Insidetherows,theweedswereremoved manuallywhenevernecessary.

2.3. Soilsampling

SoilwassampledinMarch2012,attheendof2011summer crop. Ineach plot,onedisturbed soilsample(atthree different layers;0–5,5–15and15–30cm,usingDutchaugers)andone undis-turbedsoilsample(0–10,10–20and20–30cm,bythevolumetric ringmethod)weretaken(Embrapa,1997).Thesoilsampleswere airdried,groundedandsievedthrougha2-mmsievetoremove largerpiecesofrootmaterialandthestonefraction.Allsoil sam-pleswereanalyzedinthesoillaboratoryattheFederalUniversity ofEspíritoSanto,AgricultureScienceCenter.

2.4. Soilchemicalandphysicalcharacterization

SoilchemicalandphysicalcharacterizationisgiveninTable2. ThepHwasdeterminedona 1:5soil:deionisedwaterratio;the potentialacidity(H+Al)wasextractedwithCa(OAc)2 0.5molL−1

buffered to pH 7.0, and quantified by titration with NaOH 0.0606molL−1_._Exchangeable_Ca2+_,_Mg2+_and_Al3+_were_extracted

with1molL−1_KCl_and_Na_and_K_were_extracted_with_Mehlich−1

(Embrapa,1997).Theelementcontentintheextractswere deter-minedbyatomicabsorption(Ca2+_,_Mg2+_and_Al3+_),_flame_emission

(KandNa)andphotocolorimetry(P).Theeffectivecationexchange capacity(CECE)wascalculatedbysumofcations(Ca2+,Mg2+,Na+,

K+_and_Al3+₎_and_total_cation_exchange_capacity_(CTC

T)estimatedby

thesumofbasesandpotentialacidity.Thegranulometricanalysis wasperformedbypipettemethod,50rpm,16h(Embrapa,1997).

2.5. CovercropbiomassandCinput

Covercropbiomasswascollectedinsidea1×1msquareineach plotforfreshmassdetermination.Further,itwasdriedinoven withcontinuousaircirculation(60◦_C)_for_dry_mass_{determination.} Totalcarbonofcovercropbiomasswasanalyzedbylossin igni-tionat430◦_C_for₂₄_h_in_muffle_furnace₍_Kiehl,₁₉₈₅_)._A_proportion of950gCkg−1_biomass_for_white_lupin_and_sunnhemp,₉₂₀_g_C_kg−1

biomassforblackoatandmaizeand935gCkg−1_biomass_for

inter-cropwerefoundafteranalysis.Thefactorof 1.724wasusedto convertorganicmatteroforganiccompostintoorganicCbasedon theassumptionthatorganicmattercontains580gCkg−1_biomass

(CarmoandSilva,2012;SoilSurveyStaff,1996).

2.6. Soilphysicalattributes

Undisturbedsoilsamplesweresaturatedinwaterfor24hand thenplacedinasandtensiontableof−6kPa.Soilmicroporosity (Mic)wascalculatedafterstabilizationofwaterintothe

volumet-ricring(72h).Bulkdensity(BD)wasperformedbythevolumetric ringmethodandparticledensity(PD)wasdeterminedbythe vol-umetric flaskmethod(Embrapa,1997).Totalporosity (TP) was calculatedusingthefollowingequation:

where BD is bulk density (gcm−3₎ _and _PD _is _particle _density

(gcm−3_). _{Macroporosity}₍_M

ap) wascalculated as the difference

betweentotalporosityandmicroporosity(Embrapa,1997).

2.7. Soilorganiccarbonandnitrogen

Soilsubsamplesofapproximately20gwerecrushedinamortar topassa250␮mmesh,andthenanalyzedfortotalsoilorganic

car-bon(totalorganicC),totalnitrogen(totalN),labilecarbon(Clabil)

andrecalcitrantcarbon(Crecal).TotalsoilorganicCwasperformed

bywetoxidationwithK2Cr2O7 0.167molL−1 inthepresenceof

sulfuricacidwithexternalheating(YeomansandBremner,1988). TotalNwasobtainedbysulfuricaciddigestionfollowedby Kjel-dahl distillation(Bremmerand Mulvaney, 1982;Tedesco et al., 1995).ThefractionsofsoilorganicCwereestimatedthrougha modifiedWalkelyandBlackmethodasdescribedbyChanetal. (2001)using2.5,5and10mLofconcentratedH2SO4resultingthree

acid–aqueoussolutionratiosof0.25:1,0.5:1and1:1(which corre-sponded,respectivelyto3,6and9molL−1 _H

2SO4).Theamount

of soilorganicC determinedusing2.5, 5and 10mLof concen-tratedH2SO4whencomparedwithtotalC,allowedseparationof

totalCintothefollowingfourfractionsofdecreasingoxidizability: FractionI(verylabile)organicCoxidizableunder3molL−1_H

2SO4;

FractionII(labile)thedifferenceinsoilorganicCextractedbetween 6and3molL−1_H

2SO4;FractionIII(lesslabile)thedifferenceinsoil

organicCextractedbetween9and6molL−1_H

2SO4;andFractionIV

(non-labile)residualorganicCafterreactionwith9molL−1_H 2SO4

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Table1

Operationalscheduleconductedannuallyintheno-tillandconventionaltilltreatmentsfrom2009to2013.

---2012--- ----2013---Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb

---Summer--- ---Fall--- ---Winter--- ---Spring--- ---Summer---Soil sampling1

Soil CO2-C emission and soil sampling2

Winter crop - Cabbage Cover crop sown3

Cover crop mowed Cabbage planting Plowing- Rotary hoe4 Organic compost Hand weeding

Summer crop - Eggplant Cover crop sown5

Cover crop mowed Eggplant planting Plowing- Rotary hoe 4 Organic compost

1_{Determination}_of_total_organic_C_and_N,_recalcitrant_and_labile_C;2_{Determination}_of_microbial_biomass_C,_soluble_C_and_water_content_of_soil;3_Black_oat_and_White_lupin; 4_Only_for_conventional_till_treatment_and_there_was_no_cover_crop_in_conventional_till;5_Maize_and_Sunnhemp;_Dates_of_soil_CO

2 Cemissionandsoilsampling2:14/03/12;

22/05/12;10/08/12;2510/12;06/02/13.

2.8. SoilCO2 Cemissionandsoiltemperature

MeasurementsofCO2 CemissionsweremadeonMarch,May,

August,October2012andFebruary2013.CO2 Cemissionswere

measuredusingaportableLI-8100analyzer(LiCor,EUA)coupled toadynamicchamber(LI-8100-102),knownassurveychamber, having10cmdiameterplacedonPVCsoilcollarsinsertedinthe soil(5cmdepth)beforetheexperiment.Measurementswerebased onsixreplicatesin each treatmentandlasted forover 1.5min, duringwhichtimemeasurementsofCO2 Cconcentrationswere

madeinside thechamberat 3-sintervals.AnnualCO2 C

emis-sions werecalculated basedon themeanof allmeasurements. Soiltemperatures(5.0cmdepth)weredeterminedduringthegas fluxmeasurements.TherelationbetweenCO2 C(FCO2 C)andsoil

temperature(Tsoil)wasdescribedbythefollowingequation:

FCO2=F0×exp(b×Tsoil), (2)

with the natural log (Ln) of the CO2 C emission we

have Ln(FCO2 C)=Ln(F0×exp(b×Tsoil)), the result is

Ln(FCO2 C)=Ln(F0)+b×Tsoil. A linear relationship between

Ln(FCO2 C)andtheTsoilisexpectedwheresoiltemperatureisa

limitingfactor.Basedonthebcoefficientsitispossibletoderive theQ10factor,whichrepresentsthepercentageincreaseinCO2 C

emissionfora10◦_C_increase_in_soil_temperature._This_is_derived_as Q10=e10×b(Carvalhoetal.,2012).

2.9. SoilwatercontentandmicrobialbiomassC

Ineachplot,disturbedsoilsampleswerecollectedat5cmdepth todeterminatesoilwater content,microbialbiomass C,soluble carbon(Csol)andmetabolic(Qmet)andmicrobialquotient(Qmic).

SoilsampleswerecollectedinMarch,May,August,October2012 andFebruary2013.Thethermogravimetricmethod(105–110◦_C for 24h) was usedto determine soil water content (according toEmbrapa,1997).TheCcontentinthemicrobialbiomasswas determinedbytheirradiation-extractionmethod(accordingtothe methodologydeveloped byFerreiraet al.,1999).TheC content extractedby0.5MK2SO4(calibratedpH6.5–6.8)innon-irradiated

sampleswasusedtoestimatesolubleC.Metabolicquotientwas determinedbytheratiobetweenthesoilCO2 Cemissionrateper

Table2

Chemicalandphysicalcharacterizationofthesoilsunderdifferentmanagementsystemsintheexperimentalsite.

Treatment pH P K Na Ca Mg Al CECT V Sand Silt Clay

H2O mgdm−3 cmolcdm−3 % gkg−1

0–5cm

Grass 6.40 2774.80 324.00 35.33 4.15 1.56 0.00 11.86 56.45 580.34 122.04 297.61

Leguminous 6.44 2882.95 328.67 22.83 4.61 1.42 0.00 11.48 61.32 524.07 139.98 335.95

Intercrop 6.43 3243.03 490.00 92.33 4.76 1.74 0.00 8.16 100.00 497.24 144.25 358.51

Conventionaltill 6.51 3224.14 360.50 68.00 8.04 2.43 0.00 16.25 72.22 461.87 138.25 399.87

5–15cm

Grass 6.37 1676.10 347.67 20.50 4.11 1.13 0.00 11.09 55.85 583.38 113.82 302.80

Leguminous 6.35 1293.10 304.83 14.83 4.11 1.10 0.00 9.83 63.14 557.35 117.05 325.60

Intercrop 6.32 1389.63 285.50 22.33 4.87 1.14 0.00 6.83 100.00 485.70 130.17 384.12

15–30cm

Grass 6.35 778.96 230.67 11.67 3.12 0.89 0.00 9.08 51.11 616.70 89.44 293.87

Leguminous 6.48 661.15 285.50 6.83 3.44 0.75 0.00 4.95 100.00 580.98 106.35 312.67

Intercrop 6.23 475.30 247.33 3.33 2.87 0.77 0.00 4.29 100.00 495.64 127.69 376.68

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Table3

Meanvaluesoffreshmass,drymassproductionandCinputduringwinterand summercovercrop.

Greenmanure Freshmass Drymass Cinput

Mgha−1

Meansfollowedbythesameletter,inthesamecolumn,donotdifferbyTukey’stest (p<0.05).Cinput=Cdrymassofcovercrop+Coforganiccompost.

microbialbiomassCunit.Microbialquotientwascalculatedbythe ratiobetweenmicrobialbiomassCandtotalsoilorganicC(Ferreira etal.,1999).

2.10. CbalanceandCO2equivalent

Carbonbalancewascalculatedbydifferencebetweenannual averageof CO2 C emissionsand C input(organiccompost and

greenmanure).Asvegetablescrophadsimilaryieldsandthus sim-ilarvaluesofcropresidues,theCinputaccountedreferstotheC ofgreenmanuresandorganiccompost.Theequivalencebetween CandCO2wasbasedonthemolecularweightsoftheelements,in

whichonemolofCO2contains12.011gC.

2.11. Dataanalysis

PearsoncorrelationswereperformedbetweensoilCO2 C

emis-sions, soil water content and soil temperature between no-till andconventionaltill.Dataweresubmittedtoanalysisofvariance (ANOVA)andmeansbetweentreatmentswerecomparedusingthe leastsignificantdifferenceofaTukeytest(p<0.05)intheSAEG soft-ware(Funarbe,2007).Split-plotanalysisofvarianceforsoilCO2 C

emission,soiltemperature,soilwatercontent,microbialbiomass C,solubleC,metabolicquotientandmicrobialquotientwere per-formed.Standarderrorwascalculatedfromthestandarddeviation ofthedatasetofallreplicates.

3. Results

Meanvaluesoffreshmass,drymassproduction andCinput ofcovercropsaregiveninTable3.Duringthewintercrop,fresh massproductionofwhitelupinwassignificantlylowerthanblack oatandintercrop.Nosignificantdifferenceswererecordedin win-ter cropfordry massproductionand C input.Insummercrop, freshmassproductionofmaizewassignificantlyhigherthanthat ofsunnhemp.Thisresultwasalsoobservedfordrymass produc-tion.TheCinputwassignificantlyhigherinmaizeplotsthanthe sunnhempplotsinsummercrop.

Microporosity(Mic), macroporosity (Mac), total porosity(TP),

bulk density (BD) and particledensity (PD)values aregiven in

Table4. Highermicroporosityvalues wererecordedat0–10cm layer for all plots. Conventional till showedsignificantly lower (p<0.05)microporosityandhighermacroporosityascomparedto theno-tilltreatment.Therewerenodifferencesbetweenno-till andconventionaltillupto20cmdepthfortotalporosity.Theratio betweenmacroporosityandtotalporosityindicatesthatno-tillhas higherwaterholdingcapacity.Bulkdensitytendedtoincreasewith soildepth.

MeanvaluesoftotalorganicC,totalN,C/Nratio,labileCand recalcitrantCaregiveninFig.2.Ingeneral,asdepthincreased,total organicC,totalN,ClabilandCrecaltendedtodecrease.The0–5cm

layer had the highest C and N contents. Higher (p<0.05) total organicCwasrecordedintheintercroptreatment(50.48gkg−1₎_as

comparedtoconventionaltillat0–5cmlayer(43.74gkg−1_)._There

wasnostatisticaldifferencefortotalNamongalllayersevaluated. TotalNrangedfrom2.81to5.34gkg−1_in_grass_while_in

conven-tionaltillitrangedfrom2.54to4.51gkg−1_._The_C/N_ratio_tended_to

increasewithincreasingsoildepth.IntercropshowedhigherC/N ratioforallsampledsoillayers.Conventionaltillshowed signifi-cantlylowermeansofClabilascomparedwithgrassupto15cm

soildepth.HigherCrecalwasrecordedfortheintercropwhen

com-paredwithgrass at0–5and15–30cmlayer.Crecal tendedtobe

higher at5–15cm layerfortheintercrop whencompared with grass. However, nostatistical significance wasobserved. C and

Table4

Meanvaluesofmicroporosity(Mic),macroporosity(Mac),totalporosity(TP),bulkdensity(BD)andparticledensity(PD)amongdifferentvegetablecroppingsystems.

Treatment Mic Mac TP Mac/TP BD PD

m3_m−3 _g_cm−3

0–10cm

Grass 0.47a 0.16b 0.63a 0.25b 0.98a 2.70a

Leguminous 0.48a 0.16b 0.64a 0.25b 0.98a 2.71a

Intercrop 0.48a 0.14b 0.61a 0.22b 0.99a 2.57b

Conventionaltill 0.41b 0.24a 0.65a 0.36a 0.95a 2.72a

10–20cm

Grass 0.42a 0.16a 0.57a 0.27a 1.15a 2.72ab

Leguminous 0.42a 0.16a 0.58a 0.28a 1.12a 2.65b

Intercrop 0.42a 0.19a 0.61a 0.31a 1.15a 2.92a

Conventionaltill 0.41a 0.18a 0.59a 0.31a 1.14a 2.81a

20–30cm

Grass 0.41a 0.13b 0.54b 0.24b 1.19ab 2.61b

Leguminous 0.42a 0.13b 0.55ab 0.24b 1.21a 2.73ab

Intercrop 0.42a 0.16ab 0.58ab 0.27ab 1.19ab 2.83a

Conventionaltill 0.42a 0.18a 0.60a 0.31a 1.13b 2.83a

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Fig.2.Meanvalues(n=6)oftotalorganicC(a),totalN(b),C/Nratio(c),labileC(d)andrecalcitrantC(e)inthedifferentplantingsystems.Meansfollowedbythesame letter,didnotdifferbyTukey’stest(p<0.05).Horizontalbarsrepresentstandarderrorofthemean.Grass:no-tillondeadmulchofgrass.Leguminous:no-tillondeadmulch ofleguminous.Intercrop:no-tillondeadmulchofgrassandleguminous.

N stockvalues in thedifferentvegetablesplantingsystems are giveninTable5.Cstocksweresignificantlyhigherinthe inter-crop(131.2Mgha−1₎_when_compared_with_the_other_treatments.

Conventional till showed C stock of 105Mgha−1_. _N _stock _was

12.2Mgha−1_in_grass_and₁₀_Mg_ha−1_in_conventional_till.

3.4. SoilCO2 Cemissionandsoiltemperature

CO2 CemissionsandsoiltemperaturevaluesaregiveninFig.3.

LowestCO2 CemissionswererecordedinallplotsduringMay

Table5

Carbonandnitrogenstocksvaluesinthedifferentplantingsystems(Mgha−1₎_in_the

sampledsoilprofile(0–30cm).

Treatment Grass Leguminous Intercrop Conventionaltill

Carbonstock 115.8b 110.9b 131.2a 105b

Nitrogenstock 12.2a 10.4a 10.4a 10a

Grass:no-tillondeadmulcheofgrass.Leguminous:no-tillondeadmulcheof legu-minous.Intercrop:no-tillondeadmulcheofgrassandleguminous.Meansfollowed bythesameletter,inthesamerow,donotdifferbyTukey’stest(p<0.05).

and August2012(Fig.3a).Meanannual CO2 C emissionswere

4.2; 3.64; 3.46 and 2.96␮mol CO2m−2s−1 in grass, intercrop,

leguminous andconventional till,respectively. Thesevaluesare equivalenttoanannualeffluxof15.89;13.77;13.09and11.20Mg C CO2ha−1year−1,respectively.SignificantlylowerCO2 C

emis-sions were recorded in the conventional till treatment during March2012,ascomparedwithothertreatments.CO2 Cemission

valuesgraduallyincreasedfromMay2012toFebruary2013. Dur-ingFebruary2013,theaverageCO2 Cemissionswerehigherinthe

conventionaltill,withnodifferencesamonggrassandintercrop. Soiltemperature showedsimilarseasonaldynamics,presenting loweraveragesinthewinter(August2012)andhighermean val-uesin thesummer (March 2012and February 2013) (Fig. 3b). Annual average soil temperature was 21.18; 21.15; 20.93 and 23.95◦_C _for _grass, _leguminous, _intercrop _and _conventional _till, respectively. Significantlyhighersoiltemperature wasrecorded in conventional till for all study periods (except for October 2012), when compared with no-till treatments. The Q10 factor

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Fig.3. CO2 Cemissions(a)andsoiltemperature(b)inthedifferentplantingsystems.Samecapitallettersindicatenosignificantdifferencesamongmonthsandsame

lowercaselettersrepresentnosignificantdifferenceswithinmonthsforthedifferenttreatmentsbyTukey’stest(p<0.05).Verticalbarsrepresentstandarderrorofthemean. Grass:no-tillondeadmulchofgrass.Leguminous:no-tillondeadmulchofleguminous.Intercrop:no-tillondeadmulcheofgrassandleguminous.

treatment,showinglesssensitivitytoincreasesinsoil tempera-ture.

3.5. SoilwatercontentandmicrobialbiomassC

Soilwatercontent,microbialbiomassC,solublecarbon(Csol),

metabolic (Qmet) and microbial quotient (Qmic) are given in

Fig. 4. The annual averagesoil water content (gg−1₎ _followed

the order:intercrop (0.28gg−1₎_>_grass _(0.27_g_g−1₎_>_leguminous

(0.27gg−1₎_>_conventional_till_(0.20_g_g−1_)._{Significantly}_lower_soil

water content wasrecorded in theconventional till,compared with those of no-till for all study periods (Fig. 4a). There was a significantassociation among soil water content, micro-bial biomass C, soluble C, metabolic and microbial quotient in the five periodsstudied. Microbialbiomass C decreased in the coldermonths(fromMaytoOctober2012)andincreasedinthe warmer period (after October 2012), which coincided with the highersoiltemperatures(Fig.3b)andsoilwatercontentvalues (Fig.4a).

AnnualaveragemicrobialbiomassCwas433.00;378.67;380.63 and246.77mgkg−1 _for_grass,_leguminous,_intercrop_and

conven-tionaltill,respectively.For allstudyperiods,significantlylower (exceptFebruary2013)microbialbiomassCwasrecordedin con-ventionaltill,comparedwiththoseoftheno-tillsystems(Fig.4b). LowersolubleC contentswererecordedinAugust andOctober 2012(Fig.4c). AnnualaverageofsolubleCwas133.04;147.87; 126.75and 148.42mgkg−1 _for_grass,_leguminous, _intercrop_and

conventionaltill,respectively.Therewerenodifferencesamong treatments for soluble C in August and October 2012. Lowest metabolicquotientwasrecordedduringMarch,MayandAugust, graduallyincreasingfromMay2012toFebruary2013(Fig.4d). Annualaveragemetabolicquotientwas1.58;1.50;1.60and2.01 forgrass,leguminous,intercropandconventionaltill.Significantly highermetabolicquotientwasrecordedintheconventional till

treatmentinOctober2012,comparedwiththeno-tilltreatments. Significantlylowermicrobialquotient(exceptFebruary2013)was recordedinconventionaltill.Annualaveragemicrobialquotient was9.69;7.84;7.54and5.64%forgrass,leguminous,intercropand conventionaltill.

Cbalancebetweenannualinput(covercropandorganic com-post) and annual losses(CO2 C emissions) are given in Fig. 5.

High C input in no-till is contributing to positive C balance. The difference between C input and C emitted (CO2 C

emis-sions)was9.65;5.50and8.74Mgha−1 _in_the_grass,_leguminous

and intercrop treatments, respectively. C balance was negative in conventional till (−2.15Mgha−1_), _even _with_annual _input_of

30Mgha−1 _organic _compost. _Carbon _balance _represents _35.38;

20.16 and 32.04Mgha−1 _year−1 _of _CO

2 equivalent sequestered

forgrass,leguminousandintercrop,respectively.Conventionaltill showednegativebalanceofCO2equivalent(7.88Mgha−1year−1).

4. Discussion

Cover cropbiomassproduction wassignificantlyaffected by theseason,reasonablyduetothevariationofclimaticconditions (Fig.1).Theaveragerainfallduringthesummercropping cycle (December–March)wasindeed85%higherthaninwinter crop-pingcycle(June–September).Theresultssuggestthathigherwater availabilityandincreasesintemperature(Fig.1)contributedtothe highcovercropbiomassproductionduringthesummercropby maize andsunnhemp, aswellasCinput.Theamountof above ground biomass produced is probablydue to moresuitable air temperaturesand rainfallwhichoccurredthroughoutthecover

Table6

ParametersofthemodelbetweenCO2 Cemissionsandsoiltemperature,andQ10factorinthedifferentplantingsystemsduringthestudiedperiod. Treatments Ln(CO2 Cemission)=a+(b×Tsoil)

a b R p Q10

Grass 1.070±0.184 0.016±0.008 0.341 0.065 1.170±0.189

Leguminous 0.494±0.193 0.034±0.009 0.582 <0.001 1.404±0.198

Intercrop 0.947±0.200 0.015±0.009 0.297 0.111 1.160±0.209

Conventionaltill 0.398±0.263 0.027±0.010 0.424 0.020 1.310±0.289

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Fig.4.Watercontentofsoil(a),microbialbiomassC(b),solublecarbon(c),metabolic(d)andmicrobialquotient(e)inthedifferentplantingsystems.Samecapitalletter indicatenosignificantdifferencesamongmonthssampledandsamelowercaserepresentnosignificantdifferenceswithinmonthsforthedifferenttreatmentsbyTukey’s test(p<0.05).Verticalbarsrepresentstandarderrorofthemean.Grass:no-tillondeadmulchofgrass.Leguminous:no-tillondeadmulchofleguminous.Intercrop:no-till ondeadmulchofgrassandleguminous.

cropgrowingperiod.Grassespromotedhigherbiomassproduction andCinputthanleguminoustreatments.Itiswell-knownthatthe mostwidelyusedcovercropsaregrasses,whichareconsideredthe mostsuitablecovercropsandleguminousareappreciatedfortheir nitrogensupplytothevegetablecroppingsystem(Campigliaetal., 2014).Ourresultsareconsistentwithotherrecordsinthe litera-tureforcovercropbiomassproductionintropicalzones(Amado etal.,2006;Bayeretal.,2009).

Conventionaltillagepromotedincreasesinmacroporosityand decreasesinmicroporosityandbulkdensityattopsoil.Thisleadto highersoilaerationcapacityandlowerwaterholdingcapacity.The macroporositywasabovethecriticallevelforgaseousexchange, whichwasof0.10m3_m−3₍_Xu_et_al.,₁₉₉₂_)._Despite_the_reduction

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Fig.5.CBalancebetweenannualinput(covercrop+organiccompost)andannual losses(CO2 Cemissions)amongdifferentvegetablescroppingsystems.Grass:

no-tillondeadmulchofgrass.Leguminous:no-tillondeadmulchofleguminous. Intercrop:no-tillondeadmulcheofgrassandleguminous.

till,ourresultssuggestthattherearenolimitationsonsoil aera-tionandrootgrowthintheno-tilltreatments.Themicroporosity increasedforallno-tilltreatments,significantlycontributingtothe waterstorageandplantgrowth.

Theresultssuggestthatover20yearsoforganicmanagement contributedtoincreasesinsoilorganicCpools.Anorganic com-positionrichinC(302gCkg−1_organic_compost;_{corresponding}_to

9.06MgCwasaddedtothesoilonanannualbasisandincreased soilorganicCstorage.Souzaetal.(2012)reportedthat,atthesame site,totalorganicCcontentsat0–20cmwere10.1and20.3gkg−1

in1990and2009,respectively.Thisresultisprobablyduetothe organicmanagementsystempracticedfor19yearsbefore2009. Aftertheadoptionofno-tillin2009totalorganicChasincreased, reaching34.9gkg−1_at_15–30_cm_layer_at_the_intercrop_treatment

in 2012. The biomass-Cinput by cover cropand organic com-post additionlead to increases in soil organicC through more intensifiedcroppingsequenceafterno-tilladoption.However,the maintenanceofsuperficialplowinginconventionaltillinducedsoil organicCdepletionduetooxidationofthelabilefractionsoforganic matter(seealsoSilvaandMendonc¸a,2007).

IntercropsystemfavoredsoilCstoragemorethanother vegeta-blescroppingsystems.ResultsshowedthatC/Nratiosforalllayers andplantingsystemsdidnotexceed20/1,suggestinga predomi-nanceofsoilNmineralization.SoilhumustypicallyhasaC/Nratio from10/1to12/1(Griffin,1972).Inthiscontext,intercropprovides aninputoforganicmaterialwithanintermediateC/Nratio,leading toalongerperiodofgroundcoverandsynchronizationbetween thesupplyanddemandofNbythecrops(Camposetal.,2011). IntermediateC/Nratiosfavortheorganicmatterhumification pro-cess,resultinginaccumulationofrecalcitrantCandimprovingsoil ecologicalfunctions.VachonandOelbermann(2011)reportedthat intercrop plots hadintermediate rates of cropresidueC and N inputs,showingslowrateofdecayandaccumulatingsoilorganic matterintime.

4.4. SoilCO2 Cemission,soiltemperature,soilwatercontent

andmicrobialbiomassC

The results showed that, after plowing in summer crop (February2013),therewasanincreaseinCO2 Cemissionsinthe

conventionaltillplots.Thismeasurementoccurred20daysafter plowing,whilethewinter measurementoccurred50days after

plowing. Thisobserved increase canindicatesthat there wasa period immediatelyafterplowingwhen CO2 C emissionswere

higherintheconventionaltilltreatmentthaninno-till,whichwas notquantified.ItisrecognizedthatthegreatestdifferencesinC emissionsoccuratthetimeimmediatelyfollowingtillage opera-tions(Al-KaisiandYin,2005).Thus,itmayleadtounderestimation ofannualmeanofCO2 Cemissionsintheconventionaltill

treat-mentinthepresentstudy.

Overall,ourresultssuggestthatinwarmerperiodsplowingis moreharmfulthanincolderperiods,increasingCO2 Cemissions

inthevegetablescropping,regardlessofatendencyofreductionon CO2 Cemissionsinthenotilltreatments,especiallyinthe

sum-mercrop.Thisisrelatedtotheconstantinputoforganicresidues thatcoversthesoil,reducingsoiltemperatureandincreasingsoil watercontent.Whencovercropresiduesareincorporatedintothe soil,theyaresubjectedtomoresuitableconditionsofsoilwater contentandtemperatureformineralizationthantheresiduesleft onthesoilsurface(Al-KaisiandYin,2005;Campigliaetal.,2014). Inaddition,thenon-incorporationofresiduesisakeyfactortoa slowoxidation(Ghoshetal.,2012).Thus,itmayleadtoanincrease insoilwatercontentandareductionofsoiltemperatureforlonger periodswhencomparedwithresiduesincorporatedintothesoil. Soilwatercontentisastronglimitingfactorforvegetable crop-pingsystems,anditisthemostimportantfactorinfluencingthe rateofgrowing,especiallyintropicalzoneswithhigh tempera-turesandevapotranspirationrates(Tianetal.,2011;Ghoshetal., 2012).Vegetableshaveahighdependenceofsoilwatercontentfor theirdevelopment,especiallyinwarmerperiods.Ourresultspoint toahigherannualsoilwatercontentintheno-till,whencompared totheconventionaltill(0.28vs0.20gg−1_)._This_provides_better_soil

conditionsand reducestheneedfor irrigationinthevegetables fields.

The high CO2 C emissions in the grass treatment can be

explained by thehigher C/N ratio (higher C availability) when compared totheleguminoustreatment.Also,long-termorganic managementcanleadtosoilconditionswhereNisnotalimiting factorfororganicmattermineralizationbymicroorganisms(Sakai etal.,2011).No-tillandconventionalsystemusingblackoatand maizeinpre-plantingcanshowsimilarvaluesofC/Nratios(Costa etal.,2008).Rootrespirationandmicroorganismscancontribute tototalsoilrespirationasCO2effluxmeasurementsdonot

distin-guishbetweenCO2 Cemissionsfromthesetwosources(Hanson

etal.,2000).Theconstantaccumulationandsupplyofaboveground organicmattercanleadtoincreasesinthemicrobiologicalactivity andCO2 Cemissionrates(Costaetal.,2008;Netoetal.,2011)in

theno-tilltreatment.Overall,theseresultspointtoahigh capac-ity oforganicno-till vegetablessystemstoincreasesoil-quality indicatorsalongtheyears.

EcosystemproductivityandsoilorganicCturnoverarestrongly influenced by climatic and environmental conditions, where changesonCO2 Cemissionsratesmayoccurduetovariationsin

soiltemperatureunderplausibleclimatechangescenarios.Lower lossesofCwithincreasesinsoiltemperaturewererecordedinthe grassandintercroptreatments.Inthesesystems,thestabilityof organicmatterishigherthanintheotherstreatments.Such behav-iorissupportedbythehigherQ10valuesinconventionaltilland

leguminoustreatments.ThesetrendssuggestthathighCsolfrom

conventionaltillandleguminouscancontributetotheincreased sensitivityofCO2 Cemissionstosoiltemperature.LabileC

frac-tionsarerapidlymineralizedbymicroorganisms,increasingCO2 C

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qualityindicatorintropicalzones(Balotaetal.,2004).Thehigher microbialbiomassCinno-tilltreatmentswasprobablyrelatedto thegreaterresidueinputsandconsequentlythehigherproportion ofreadilymetabolizedmaterials,suchassugars,aminoacidsand organicacids,enhancingmicrobialbiomassC(Tianetal.,2011).

The handweeding that occurredin August/September 2012 promotedincreasesinthemetabolicquotientintheconventional tilltreatmentinOctober2012.Thisshowsthepotentialofno-till toreducesoildisturbance, sincehandweedingwasnotapplied becausecovercropalsoseemstobeasuitableapproachfor con-trollingtheweeds(Campigliaetal.,2014).LowQmetratesunder

no-tillindicatestheestablishmentofanefficientmicrobial popula-tion,promotingCincorporation.Thisisveryimportanttomaintain soilCstorage.HighQmetratesareindicativeofagriculturalsystems

subjectedtohighstressconditions(AndersonandDomsch,2010), asisthecaseoftheplotssubjectedtoconventionaltill.Indisturbed systems,microbialbiomassrequiresmoreC toitsmaintenance. Microbialquotientindicatestheamountofmetabolicactive car-boninthetotalsoilorganicmatterandthus,reflectsthemicrobial Ccyclingandstabilization(AndersonandDomsch,2010).LessC wasimmobilizedinmicrobialbiomassinconventionaltillsystem, resultinginlowCandnutrientcyclingrates,asindicatedbythe lowerannualaverageofmicrobialquotient.Microbialquotientof <1%isareliableindicatorofreducedCturnoverinsoils(Joergenson etal.,1994).Themicrobialquotientrecordedunderdifferent treat-mentsvariedfrom4.2to10.3%(Fig.4e)whichisslighthigherthan thefindingsofBalotaetal.(2004)fortropicalzones.Highvaluesof microbialquotientinthepresentstudyareexpectedduethe long-termorganicmanagementinthestudiedsite.Theresultsindicatea highCturnoverintheno-tilltreatments,asitisexpectedinsoilsof tropicalzonesaroundtheworld(Ghoshetal.,2012).Thus,organic no-tillvegetablessystemsprovidedamorefavorableenvironment forrapidmicrobialgrowth,amoreeffectiveCstorageonmicrobial biomass,andactedasasourceofnutrientsforvegetablegrowth.

AlthoughtherearesubstantialincrementsinCO2 Cemissionin

theno-tillsystems,itisextremelyimportanttotakeintoaccount theCbalancebetweeninput,lossesandpotentialofsoilCstorage.

Jia et al. (2012) reported that theC entered into organic veg-etablesystemsweremainlythroughorganicamendmentandcrop residue,andtheyaccountfor23–73%and11–16%,respectively,of thetotal Cincrease.Theconventionaltillsystempresented ele-vatedClossesthroughCO2 Cemissionand incorporatedlessC

tothesoilthantheno-tillsystem.NegativeCbalance(Fig.5)was recordedintheconventionaltill,evenwiththeannualinputof 30Mgha−1_year−1_of_organic_compost_in_the_winter_and_summer.

AssumingaCpriceof$42perMgofCsequestered(Takimotoetal., 2008),CO2 equivalentin thisstudycan correspondto$1484.7;

$846.72and$1345.68sellingCcreditsamonggrass,leguminous andintercrop,respectively.Souzaetal.(2012)reportedanincrease of 86.62tCO2 equivalentin 10 years due organicmanagement

ofvegetablesatthesameexperimentalsite.Theirvalueislower thanthepresentedinthisstudyduethecontributionofcovercrop andorganiccompostafterno-tilladoption.Theseresultsshowthat organicno-tillvegetablessystemsmayalsopromotefinancial sus-tainabilitytothefarmerbyCsequestration,whichisnotevidenced inconventionaltill.

5. Conclusions

Organicno-tillvegetablessystemscouldincreaseC sequestra-tionandimprovesoilqualityintropicalzones,especiallywithinthe domainoftheAtlanticForest.Themaintenanceofconventionaltill

reducedsoilorganicmatter,adverselyimpactingsoilorganicC sta-tus.CO2 Cemissionswerehigherinno-tillthaninconventional

tillage.However,immobilizationofCinthemicrobialbiomasswas moreefficientunderno-till,promotingapositiveCbalanceinthe soilleadingtoaCsink.Organicno-tillvegetablessystemsshould beencouraged onvegetablescropping systemsto improvesoil qualityoftheagriculturallandwithinthedomainoftheAtlantic Forestbiome.Implementationofgrass/leguminousintercropping shouldbestimulatedonorganicvegetableproduction.However, thispreliminaryfindingneedstobefurtherinvestigatedby includ-ingenergybalanceanalyses,sincetheoperationscarriedoutinthe covercroptreatmentsdemandedseveralworkhoursandhuman power.Thiscanbeadisadvantageofno-tillmanagement. Never-theless,croppingsystemsintropicalareasshouldattainabalance betweensoilconservationandeconomicalgains.

Acknowledgments

The authors thank INCAPER (Espírito Santo Institute for Research,TechnicalAssistanceandRuralExtension)forthestudy in partnership, the Brazilian sponsors CAPES (Coordination of Improvement of Personal Higher Education), CNPq (National CounselofTechnologicalandScientificDevelopment)andFAPES (FoundationforResearchSupportoftheStateofEspíritoSanto)for grantingfinancialsupportandscholarships.

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