Cucumber (Cucumis sativus, L.) water use efficiency (WUE) under plastic mulch and drip irrigation

(1)

ContentslistsavailableatScienceDirect

Agricultural

Water

Management

jo u r n al ho m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / a g w a t

Cucumber

(Cucumis

sativus,

L.)

water

use

efﬁciency

(WUE)

under

plastic

mulch

and

drip

irrigation

T. Yaghi

a,∗

_,

_A.

_Arslan

a

_,

_F.

_Naoum

b

a_The_General_Commission_for_Scientiﬁc_Agricultural_Research,_GCSAR,_Syria b_Department_of_Rural_Engineering,_Faculty_of_Agriculture,_Aleppo_University,_Syria

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received25November2012 Accepted1June2013 Keywords: Dripirrigation Surfaceirrigation Plasticmulch Yield WUE Soiltemperature

a

b

s

t

r

a

c

t

Tostudytheeffectoftwotypesofplasticmulch(transparentandblack)withdripirrigationonwater requirementandCucumber(Cucumissativus,L.)yield,inadditiontotheireffectonMaturitytime.Trials werecarriedoutatTeezenResearchStation,HamaAgriculturalResearchCenter,GCSAR,Syria, dur-ing2009–2010growingseasonsusingcompleterandomizedblockdesignwiththreereplicates.Soil characteristicswerefollowedtoobecausetheyreﬂecttheeffectsofplasticmulch.Treatmentswere transparentmulcheddripirrigation(DI+TM),blackmulcheddripirrigation(DI+BM),dripirrigation withoutmulching(DI)andsurfacefurrowirrigation(SI).Theresultsofthestudyindicatedthat(DI+TM) treatmentexcelledallothertreatmentsatyieldandwateruseefﬁciency(WUE),whereitsyieldwas 63.9tha−1,and(WUE)was0.262tha−1mm−1,while(DI+BM)treatmentproduced57.9tha−1,witha (WUE)of0.238tha−1mm−1.HowevercucumberyieldandWUEdeclinedintheremainingtreatmentsof nomulch(DI)and(SI)toreach44.1tha−1_with_0.153_t_ha−1_mm−1_and_37.7_t_ha−1_with_0.056_t_ha−1_mm−1_, respectively.Theresultsshowedthat(DI+TM)treatmentgavethehighestsoiltemperatureandmoisture duringbothoftheseasonsincomparisonto(DI+BM).Thisenhanceditsvegetativegrowthandalmost doubleditsproductivitycomparedtotheSItreatment.

1. Introduction

Cucumberdemandshightemperaturesand soilmoisturefor satisfactoryyield,andunderunfavorableclimaticconditions, sev-eralproblemsmayoccur,suchasthereductionoffemaleﬂowers (Cantliffe,1981),delayinfruitgrowth(Liebig,1981;Marcelisand BaanHofman-Eijer,1993;Medanyetal.,1999)andmineral disor-ders–(BakkerandSonneveld,1988).Therefore,plantingisusually madeinthespring-summerseasonwhentheweatherconditions arefavorableforplantsgrowthandhighyieldcouldbeachieved.

Syriahasabundantlandresourcesbuttheirrigationwater sup-plyismuchlessforadequatelyexploitingthesoilpotentials.This calls for adoption of advanced irrigationmethods such as drip irrigationforeffectiveuseandmanagementofthelimitedwater resources.

Irrigationisanimportantlimitingfactorofcropyield,because it isassociated withmany factorsof plantenvironment, which

∗ Correspondingauthor.Tel.:+963115756012;fax:+963115757992. E-mailaddress:Tammamyaghi@Yahoo.com(T.Yaghi).

inﬂuence growth and development. Availability of adequate amountofmoistureatcriticalstagesofplantgrowthnotonly opti-mizesthemetabolicprocessinplantcellsbutalsoincreasesthe effectivenessofthemineralnutrientsappliedtothecrop. Conse-quentlyanydegreeofwaterstressmayproducedeleteriouseffects ongrowthandyieldofthecrop(Saifetal.,2003).Surfaceirrigation methodis mostwidelyusedall overtheworld (Mustafa etal., 2003).

InSyriacucumberisgenerallygrownunderconventional sur-faceirrigationmethodtoo.Inthismethod,themajorproportion ofirrigationwaterislostbysurfaceevaporation,deeppercolation andotherloses,resultinginlowerirrigationefﬁciencies.Moreover, thereis atendencyoffarmerstoapplyexcesswater whenitis available(Jainetal.,2000).Underlimitedwatersupplyconditions farmerstendtoincreaseirrigationinterval,whichcreateswater stressresultinginlowyieldsandpoorquality.

Dripirrigation,withitsabilitytoprovidesmallandfrequent waterapplicationsdirectlyinthevicinityoftheplantrootzone hasattractedinterestbecauseofdecreasedwaterrequirementand possibleincreaseinproduction(Darwishetal.,2003;Janat,2003). Astheworldincreasinglybecomesdependentontheproduction of irrigated lands, irrigated agriculture facesserious challenges thatthreatenitssuitability.Itisprudenttomakeefﬁcientuseof waterandbringmoreareaunderirrigationthroughavailablewater resources.Thiscanbeachievedbyintroducingadvancedmethods

http://dx.doi.org/10.1016/j.agwat.2013.06.002

Open access under CC BY-NC-ND license.

(2)

150 T.Yaghietal./AgriculturalWaterManagement128 (2013) 149–157

Table1

Someselectedsoilchemicalandphysicalproperties.

Depth(cm) pH1:5 EC(dSm−1) Avail-P(mg/kg) Avail-K(mg/kg) Mineral-N(mg/kg) CaCO3% OM% Sand% Silt% Clay% Soiltexture

0–30 7.8 0.22 9.5 507.5 2.97 5.66 0.77 14 15 71

Clay(Vertisol)

30–60 7.8 0.21 5.3 350 3.28 5.44 0.59 13 16 71

P,phosphorus;K,potassium;N,nitrogen.

ofirrigationandimprovedwatermanagementpractices(Zaman

etal.,2001).Amongthewatermanagementpracticesfor increas-ingwateruseefficiencyWUEoneofthemismulching.Anymaterial spreadonthesurfaceofsoiltoprotectitfromsolarradiationor evaporationiscalledmulch.Differenttypesofmaterialslikewheat straw,ricestraw,plasticfilm,grass,wood,sandetc.areusedas mulches.Theymoderatesoiltemperatureandincreasewater infil-trationduringintensiverain(Gajrietal.,1994; Khurshid etal., 2006).

Alargenumberofexperimentshavebeenconductedtostudy theeffectofdripirrigationandplasticmulchonyieldimprovement ofmanycropsindifferentagro-climaticregionandsoilcondition. About20–60%higheryieldswereobtainedwithdripirrigationin somestudies(Sivanappanetal.,1974),whileinotherstudiesyield wasreportedtobeslightlylowerorequaltothatofconventional irrigation(DossandEvans,1980)alongwithreductioninirrigation requirementof30–60%.

Cucumberisalsosuitedtodripirrigationincombinationwith plasticmulch,butlittleworkhasbeendonetostudytheeffects of dripirrigation and plastic mulch on cropyield and WUE of cucumberinsemiaridlandsofSyria.Thepresentinvestigationwas plannedtodeterminetheeffectsofdripirrigationandplasticmulch oncucumberyieldandWUE,inadditiontotheireffectsonthefate ofwaterinthesoilsection.

2. Materialsandmethods

Theﬁeldexperimentswerecarriedoutduringtwosuccessive growthseasonsof2009and2010,atTeezenresearchstation, Agri-culturalResearchCenter,Hama,Syria.Thesitewaslocatedat307 altitude,35.1◦Nlatitudeand36.5◦Elongitude.Wherethesummers aredryandhot,whilewintersarecold.

Thesoiloftheexperimentalplotcanbeclassiﬁedasredclay Vertisolwithbulkdensityintheupper30cmof1.15g/cm3_and_the

underlayertill60cmwas1.17g/cm3_.

Compositesoilsamples(0–30 and30–60cm)werecollected beforeplantingindicatedthatpHwas7.8,andavailable phospho-ruswerepoor,whileithadrichcontentofavailablepotassium. SomephysicalandchemicalsoilpropertiesaregiveninTable1.

Cucumberseed(Cucumissativus,L.,“F1Hybridprince”)were sownmanuallyinholesonJune10th2009–2010,ononesideof eachfurrowbykeepingrow-to-rowandplant-to-plantdistance 1.5mand40cm,respectively.

Thelayout ofthe experiment wasa completelyrandomized blockdesign withthree replications for each of thefour treat-mentstested,[transparentmulcheddripirrigation(DI+TM),black mulcheddripirrigation(DI+BM),dripirrigationwithoutmulching (DI)andsurfacefurrowirrigationwithoutmulch(SI)]asshownin (Fig.1).

Theexperimentalareawas4800m2_,_divided_into_three_blocks.

Eachblockconsistedoffourplots,4.5m×40meach.Aborderof threemeterseparatedboththeblocksandplots.Eachplothadthree rows,1.5mapartand40mlong,Inordertopreventthewaterin anyoneplotfromaffectingitsneighboringplots.Inboth grow-ingseasons,moldboardplowanddiskharrowwereusedfortillage operationsandafurrowerwasusedformakingfurrows(40mlong, 75cmwideand50cmdeep)intheSItreatment.Soilmoisturewas determinedusingneutronprobe(Troxler,4300)fordepthbelow

15cm.Neutronprobewascalibratedintheﬁeldbycorrelating neu-tronprobecountratiowithvolumetricwatercontentmeasuredby gravimetricmethodandbulkdensity.

A125cmneutronprobetubeswereinstallednearthecenter ofeachplotbetweentwoplantsanddistanced15,30,45,60and 75cmfromirrigationline.Moisturereadingsweretakenat15cm depthintervalsbeforeandaftereachirrigationfordetermination ofchangeinsoilwaterstorageanddeepwaterpercolationwhich belowtherootzoneovertime.

SURFER8softwarewasusedtographthereadingsafter obtain-ingthecalibrationcurve.Irrigationschedulingwasbasedonthe calibratedneutronprobereadings,whereasirrigationwasapplied at85%ofﬁeldcapacityaccordingtotheeffectiverootsdistribution zone.

Grosswaterrequirement(IRg)foreachplotwascontrolledby

thespecialvalvesetforthatplot,andtheexactamountsusedwere readonaﬂowmeter.Thenetirrigationrequirement(IRn)must

replenishtheactualcropevapotranspirationwater(ETa),asrainfall andothercomponentsofthewaterbalance.Thegrossirrigation requirements(IRg)mustincreasethe(IRn),inordertocompensate

theirrigationefﬁciencyandtoleachsalts: IRg=

IRn

Ea(1−LR).

where Ea: irrigation efﬁciency coefﬁcient (smaller than 1) and expressestheratio:waterstoredinthecroprootzonetobeused bythecrop/appliedwater(Jitan,2012).LR:minimumamountof leachingneededtocontrolsaltswithdripirrigationwhichequals tozeroinstudyregion.

ETa(mm/day),wasestimatedusingthefollowingformofthe waterbalanceequation(Castilla,1990;Burbaand Verma,2005; SimonneandDukes,2010):

ETa=

D(Vi−Vf)

days

where(vi−vf):isthechangeinvolumetricsoilwatercontent

betweentwomeasurementdates,D(mm):isthethicknessofsoil layer.

Datawerecalculatedasthesumofthedailyevaporationfrom class-Aopen-paninstallednearbytheexperimentalplots. Refer-encecropevapotranspiration(ET0)valueswerecalculatedbasedon

FAOPenman–Monteithmethod.Thecropcoefﬁcient,Kcfor

cucum-berwasbasicallydeterminedbytheratioofthecropETc tothe

referenceET0,whereas:Kc=ETc/ET0(FAO,1998).

TheirrigationwascarriedoutbyadripsystemofkeyClipped emitters(4l/h)spaced40cmapart,byeachplant,on16mm(ID) lat-erals,oneperrowofcucumber.Theemittersoperateatapressure of100KPa,whichwascontrolledwithbypassarrangement.

The used plastic mulch was black polyethylene (40␮m) for (DI+BM), and clear transparent polyethylene (100␮m) for (DI+TM).

Fertilizerswereappliedaccordingtosoiltestresultsand Min-istry of Agric. and Agra. Reform (MAAR) recommended levels of N (250kgha−1), P (150kgha−1) and K (350kgha−1) as urea (46%N),triplesupperphosphate(46%TSP)andK2SO4 (46%SOP),

respectively,usingDosatroninjectorindripsystem,ormanually spreadingimmediatelybeforeirrigationforSItreatment.Allother

(3)

Fig.1.LayoutofcucumberexperimentandirrigationsystematTeezenresearchstation,Hama,Syria.

Table2

Irrigationinterval,Da(days);netirrigationrequirements,IRn(mm);grossirrigationrequirements,IRg(mm),andnumberofirrigations,N,forthestudytreatments,asaverage

duringmonthsofthebothofgrowingseasons(June10untilSeptember10).

Treatment DI+TM DI+BM DI SI Month Da IRn IRg Da IRn IRg Da IRn IRg Da IRn IRg June 5 3.8 4.1 6 3.5 3.9 4 4.1 4.5 6 20.7 49.8 3.7 4.0 3.9 4.2 3.7 4.1 19.2 40.9 3.9 4.2 3.8 4.1 3.8 4.1 22.1 41.2 4.0 4.3 4.2 4.6 N=4 N=3 N=5 3.6 3.9 N=3 July 4 5.3 5.8 5 5.2 5.6 4 3.9 4.2 6 17.3 43.6 5.0 5.4 5.3 5.6 5.2 5.6 16.2 40.1 14.6 15.8 5.5 5.9 5.6 6.0 19.8 40.9 14.6 16.2 14.0 15.3 5.7 6.1 32.4 48.8 13.8 14.9 14.6 16.0 13.8 14.8 33.8 52.1 18.5 20.2 14.9 16.2 14.0 15.4 N=7 17.8 19.0 N=6 N=7 14.6 15.7 N=5 August 5 16.8 18.0 4 16.8 18.1 3 18.6 20.2 6 31.2 51.6 16.5 17.8 16.5 18.2 18.2 19.6 35.4 53.6 17.5 19.0 17.5 19.0 16.5 17.6 32.4 56.1 18.2 19.4 17.8 19.6 16.2 17.8 30.0 45.0 18.8 20.5 16.2 17.6 17.8 19.4 29.4 51.7 14.9 16.5 17.8 19.4 14.9 16.3 15.8 16.9 15.5 17.1 15.8 17.4 N=6 N=7 N=9 17.8 19.2 N=5 September 17.2 18.5 5 17.5 19.2 4 15.2 16.8 7 33.0 56.1 N=1 N=2 17.5 19.2 N=2 17.5 19.2 N=1 Total N=18 224.9 243.6 N=18 224.1 244 N=23 265.8 289.4 N=14 372.8 671.5

(4)

Fig.2.Diagramsofwatercontentinsoilafterdripirrigationsuchas(wettingbulb)comparedwithirrigationwaterdistributionpatternaftersurfacefurrowirrigation.

necessaryoperationssuchaspest andweedcontrolswere

per-formedaccordingtogenerallocalpracticesandrecommendations.

Mercurythermometerswereinstalledatthesurfaceofsoil,at

the5cmsoildepthandatthe10cmsoildepthintworeplicatesof

eachtreatment,i.e.,atotalof24thermometers.Temperaturewas

recordedfrom10June(plantingdate)tilltheendoftheseason.

Measurementsweretakeneachtwohoursofthedayontwodays

aweek.Airtemperaturewastakenfromanearbyweatherstation.

Theyield(tha−1)fromeach plotwasrecordedineach pick,

andtheeffectivenessofcucumberinusingwaterduringits

com-pletegrowthperiodisgenerallydescribedintermsofWUEandis

expressedastheratiooftotalcropyieldtothetotaldepthofwater

appliedto crop including effective rainfall during its complete

growthperiod(Steynet al.,2000;Oweis, 2012): WUE=CY/WA,

where WUE=water useefﬁciency, tha−1mm−1. CY=total crop yield, tha−1. WA=total depth of water applied, mm. Data on cucumberyieldandwateruseefﬁciency(WUE)wererecordedby usingstandardprocedures,andwerestatisticallyanalyzed.Means wereseparatedwiththeLSD0.05andLSD0.01usingGenStat7

pro-gram.

3. Resultsanddiscussion

3.1. Waterapplied

Beforeplanting,25mmirrigationwaterwasappliedtoall treat-mentstobringthesoilwatercontentin0–60cmsoildepthupto levelofﬁeldcapacity.

Irrigationschedulewerestartedmeasuringofsoilwatercontent byneutronprobe.Themaximumamountofwaterappliedtothe

cucumberwas671.5mminthe(SI)treatmentwhiletheminimum amountwas243.6mmintheDI+TMtreatmentasaverageduring bothofgrowingseasonsasshowninTable2.

Itwasnotedalmostsimilartonetorgrossirrigation require-mentsandalsonumberofirrigations(N=18)intheDI+TMand DI+BM treatments. While those parameters werehighin non-mulchedtreatmentstoreachIRn=265.8mm,IRg=289.4mmand

numberofirrigationsN=23for(DI)treatment.

TheseresultsarealsoinagreementwiththoseofTiwarietal. (2002),SamuelandSingh(2003),Erteketal.(2006)andZotarelli etal.(2009).

3.2. Watermovementinthesoil

The irrigation water was applied to compensate the water deficiency of the root zone soil (0.30m) in the first stage and the root zone soil (0.60m) after, according to FAO (1998) for cucumber effective roots distribution zone, and monitored in 0.30 depthsincrement to0.90mafter irrigationfor each treat-ment. Monitoring the soil water content in the drip irrigated plots revealed that infiltration below 0.90m depths was neg-ligible especially in mulched plots compared with that of SI plots.

Fig.2showsthesoilwatercontentsmeasuredbyNeutronprobe beforeand afterirrigation drawnby SURFER 8software. These readingsindicatethatplasticmulchinghasapronouncedeffecton dripirrigationeffectivenessthroughthegoodestimationofwetting bulb’sdimensionsunderthedripperandunderstandingits mois-turechangesinplaceandtime,whereastheuseofdripirrigation withplasticmulchreducedbothofevaporationfromsoilsurface

(5)

Table3

Waterapplied,yieldandwateruseefﬁciency(WUE)ofdifferenttreatments(meanof2009and2010).

Parameters Treatments Ftest LSD++

DI+TM DI+BM DI SI .05 .01

Waterapplied(mm) 243.6 244 289.4 671.5

Yield(tha−1₎ _63.9 _57.8 _44.1 _37.7 * _2.79 _4.23

WUE(tha−1_mm−1₎ _0.262 _0.238 _0.153 _0.056 * _0.011 _0.016

LSD++_:_The_least_signiﬁcant_difference. *_The_signiﬁcant_difference_at_1%_level.

andwaterdistributionareainsoilawayfromthelinesofirrigation, whichhasextremeeffectonirrigationwaterdistributionpattern, rootdistribution,efﬁciencyofthefertilizers,wateruseand ulti-matelyonthecucumberproductionquantityandquality,These resultsarealsoinagreementwiththose ofICARDA (2000)and Pawaretal.(2002).

Surfacefurrowirrigationreducesirrigationfrequencyfromone irrigationeveryfewdaysasdripsystemtooneeveryweekwhich reducedtheproductivity17%comparedwith(DI)treatment,and attributedtothelargerangesofsoilmoistureoftherootingzone. Similar data were reportedby Wanget al. (2006). The results showedthatthehighestsoilmoisturevalueswererecordedwith transparentplasticmulchandblackpolyethylenemulchcompared tobaresoil.Generally,allmulchesincreasedweeklymeasurements ofsoilmoistureandwateruseefﬁciency.Theseresultswereagreed withthoseobtainedbyFarias-Lariosetal.(1994a,b),Salmanetal. (1991a)andWeber(2000).Therefore,thedifferenttypesofmulch leadtoincreasingthesoilmoistureduetodecreasedof evapora-tionfromsoilsurfacecomparedtobaresoil.So,mulchesﬁnding favorablesoilenvironmentalconditionsandhadapositiveeffect ongrowthofcucumberplantsandcontributedtoincreasing vege-tativegrowthandyield.

Table2andFig.2canhelpustoderivethatapplieddripirrigation effectivenessforDI+TM,DI+BMandDIwas92%whileitdecreases to57%forSI.Thepercentofwaterusereductionwas64%,65% and57%forDI+TM,DI+BMandDI,respectively,comparedwith SI.TheseresultsarealsoinagreementwiththoseofLouiseetal. (1999),PatelandPatel(2001)andGhorbani(2003).

3.3. Wateruseefﬁciency(WUE)andyield

Thepresentstudyshowstheeffectsofdripirrigationand plas-ticmulchoncropwaterrequirementandWUE.Theresultsofthe studyindicated that DI+TMtreatment markedlydecreased the amountsofappliedwaterintheorderDI+TM≤DI+BM<DI<SIand increasedWUEintheorderDI+TM>DI+BM>DI>SI.Thehighest WUE(0.262tha−1mm−1)wasobtainedfortheDI+TMtreatment becausethistreatmentconsumedabout64%and16%lesswater thantheSIandDItreatmentsrespectively,andproduced compar-ativelyhigheryield.

ThelowestWUE(0.056tha−1mm−1)realizedfortheSI treat-mentcanbeascribedtothefactthatthe175% morewaterwas appliedtothistreatmentthantheDI+TM,whileyieldoftheSI

Table4

ActualevapotranspirationETa(mm),andlengthofcucumbergrowthstages,Lg (days),asaverageinthebothofgrowingseasons(Jun10untilSep10).

ETa(mm)Lg(days) DI+TM DI+BM DI SI Init.(Lini) 3 5 10 37 3 5 10 11 Dev.(Ldev) 31 31 34 99 29 31 30 28 Mid.(Lmid) 161 160 180 207 51 47 43 44 Late.(Llate) 18 18 22 30 10 10 10 10 Total 213 214 246 373 93 93 93 93

methodwas59%oftheDI+TMtreatment.Theseresultsarealso

in agreement with those of Doss and Evans (1980), Drost and

Hefelbower(2004),Kirnakand Demirtas(2006),Ngouajio etal. (2006)andSeyﬁandRashidi(2007).Resultsindicatedthat non-mulchedtreatments(DI andSI)receivedanaverageof246mm and 373mm,respectively toproduce44.1tha−1 and37.7tha−1 cucumber,respectively,whereastreatmentswithtransparentand black plastic mulching consumed an average of 213mm and 214mmwater,respectivelyandyieldedaverageof63.9tha−1and 57.8tha−1.TheseresultssupportthoseofWienetal.(1993),who showedthatincreasedtomatogrowthandyieldbypolyethylene mulchingisaconsequenceofenhancedrootgrowthandnutrient uptakeearlyintheseason.

Statisticalanalysesusing theF-testwerecarried out.LSDat .01and.05levelswasalsodetermined.AsshowninTable3,the resultssurely showed signiﬁcantdifferences in yield and WUE betweentreatmentsat.01level,whereastransparentmulchwith dripirrigationexceededallthetreatmentsofthestudyintheorder DI+TM>DI+BM>DI>SI.SimilardatawerereportedbyDiaz-Perez andBatal(2002),Simmsetal.(2005)andWatereretal.(2008).

3.4. Consumptivewateruse(actualcropevapotranspiration,ETa) ETa (mm) for each treatmentwas calculated duringvarious cucumbergrowthstages.ItisnotedthatSIconsumedmorewater thanDIwhich inturnconsumedmore thanDI+BMorDI+TM, whichhadsimilarvalues,asshowninTable4.Similardatawere reportedbyBattikhiandGhawi(1987).

Table5

Averagemonthlysolarradiation,minimumandmaximumtemperature,rainfall,wind,evaporationfrompanandET0duringbothofexperimentalseasons.

Month Solar(h/d) Temp(◦_C) _Rainfall_(mm) _Wind_(m/s) _E_pan_(mm) _ET₀a_(mm)

Max. Min. Jun 13 33 22 0 2.2 214 152 July 13 35 26 0 3.2 323 248 Aug 12 35 25 0 1.9 273 199 Sep 11 32 23 0 1.9 73 52 Totalseasonal 883 657

(6)

Fig.3. CucumbercropcoefﬁcientcurvesatTeezenresearchstation,Hama.

It is also explained that drip irrigation system withplastic mulches(blackandtransparent)substantiallypreventthe evapo-rationfromthesoilsurface.Associatedwiththereductionin evap-orationisageneralincreaseintranspirationfromcucumberleaves causedbythetransferofbothsensibleandradiativeheatfromthe surfaceoftheplasticcovertoadjacentvegetativeleaves. Evapora-tionincreasedespeciallyduringthefirstweeksaftertransplanting whereplantsdidnothaveenoughcanopiestoshadethesoil. Plas-ticmulchesdirectlyaffectthemicroclimatearoundtheplantby modifyingtheradiationbudget(absorptivityvs.reflectivity)ofthe surfaceanddecreasingthesoilwaterloss.Theseresultsarealsoin agreementwiththoseofJennietal.(2000),Orzolek(2000),Orzolek etal.(2003),El-Nemr(2006)andKoriretal.(2006).Table5shows theclimaticdataasaverageduringbothofexperimentalseasons. ItalsoshowspotentialevaporationratesfromclassApanwhich setsnearfieldandreferencecropevapotranspiration(ET0)values

werecalculatedbasedonFAOPenman–Monteithmethod. It wasnoted that (ET0)values reached themaximum value

duringJuly.AndalsoActual evapotranspiration(ETa)startedto increasefromthedateofsowingtillmidseasonstageandreached maximuminJulyandAugustthendeclinedagainattheendofmid andlateseasonstagesinSeptemberasshowninTable4.

3.5. Cropcoefﬁcient

Thecropcoefﬁcient(Kc)valuesdecreasedbyanaverageof35%

duetousedripirrigationwithplasticmulchwhichreducedsoil evaporationcomparedwithnon-mulchedtreatments(DIandSI), asshownin(Fig.3).Theseresultsareinagreementwiththoseof Safadi(1991),Vickers(2001)andMataetal.(2002).Alsowhenwe compareditwithcucumbercropcoefﬁcientvaluesgiveninAllen etal.(1998),wenotedthattheKc valuesalmostsimilartoones

whichwerecalculatedinSItreatment. 3.6. Soiltemperature

Soiltemperaturewasmeasuredatsoilsurfaceandtwodepths 5and10cm,each2h,respectivelyduringday,twiceaweek.The resultsarepresentedasaverageduringbothofseasons(Fig.4). Averageairtemperaturesweregenerallyhigherthansoil temper-atureswhich measuredatdepths ofun-mulched treatments.It reachedaminimumduringbothofthesecondandthirdquarters ofJune of22◦C at6a.m.,and 33◦C at14p.m. Itincreasedto a maximumof26◦Cinthemorningand35◦Cintheafternoonin July.Airtemperaturesremainedhigherthansoiltemperaturesat alldepthsinprevioustreatments exceptinbothofDI+TMand DI+BMtreatments.Thevaluesofsoiltemperaturewithmulching aremuchhigherthanthose ofsoilwithoutmulching.Thismay beowingtomulchingpreventscoolingofthesoilsurfacedueto

evaporation. The values of soil temperature under transparent mulchwerehigherthanthoseundertheblackmulch.These trans-parentplastic mulchmaypermitwarmingof6.4,5.9and5.6◦C toadepthsof0cm(soilsurface),5cmand10cm,whereasblack plasticspermitwarmingof3.1,2.7and2.4◦Catthesameprevious depths compared to the treatments without mulching. Using mulchtypes(transparentandblack)enhancedsoiltemperature.

Fig.4.Averageofsoiltemperatureundermulchedandunmulchedcucumberatthe surfaceofsoilandtwodepths5and10cm.

(7)

transparentplasticmulchincreasedsoiltemperaturemorethan blackmulchespeciallyduringtheﬁrstweeksaftertransplanting whereplantsdidnothaveenoughcanopiestoshadethesoil.The degreeoncontactbetweenthemulchandsoil,oftenquantiﬁedas athermalcontactresistance,canaffectgreatlytheperformanceof mulch.Ifanairspaceiscreatedbetweentheplasticmulchandthe soilbyaroughsoilsurface,soilwarmingcanbelesseffectivethan wouldbeexpectedfromparticularmulch.

Sunlightpassesthroughthetransparentplasticandheatsthe soil.Alayerofwaterunderneaththeplasticretainstheradiantheat atnightthroughwhatisknownasagreenhouseeffect.Blackplastic mulchabsorbsmostofthesunlightandbecomesgreatlywarmed, andlittleenergypassesthroughtowarmthesoil.Theseresults sup-portthoseofHamandKluitenberg(1994),Waterer(1999,2000), Tarara(2000),Lamont(2005)andNgouajioandErnest(2005)who showedthattransparentmulchabsorbsonly5%ofshort-wave radi-ation,reﬂectsonly11%,buttransmits84%ofshort-waveradiation, whereassurfacetemperaturesdo notreachthelevelsfoundon blackplasticduetotheirlowabsorptionratesofshort-wave radia-tion.Thatmeansthattransparentplasticsactuallyheatthesoilby transmittinglighttothesoilsurfaceratherthanconductingheat likedarkplastics.WhiledifferentlyLiakatasetal.(1986)andHam etal.(1993)explainedthatlayingtransparentmulchlooselyacross thesoilcreatesaninsulatingairgapbetweenthemulchandsoilthat resultsinhigherdaytimetemperaturesundertransparentplastic thanblackplasticmulch.Then,ifclearplasticislaidtightlyacross thebed,itseffectswillbeminimizedand,inthissituation,black plasticlaidtightlyacrossthebedwouldbemoreeffectiveatheating thesoil.

3.7. Earlierproduction(precocity)andweedcontrol

Plasticmulchesraisesoiltemperatureintheplantingbedwhich promotesfastercropdevelopmentandearlieryields.Whereas ger-minationdatesforDI+TM, DI+BM,DIand SIwere onJune 13, 15,20and21,respectively,maturitydateswereonJuly9,13,22 and 27at thesamepreviousarrangement. Alsoitis associated withthebestvegetativegrowthandsignificantlyincreased pro-ductivitylimitsof(70%,53%and17%)forDI+TM,DI+BMandDI comparedwiththeSItreatment.Increasedyieldcouldbelargely attributedtotheincreaseinsoiltemperatureduetoapplication ofplasticmulchwhichresultedinanenhancementofsoil envi-ronmentaroundrootsofcucumberplants,whichledtoincreasing plantgrowthand,hence,increasingnutrientsuptake.Hence, ear-lierproductionandhighertotalyieldwasobtained.Theseresults wereinlinewiththoseobtainedbyWienandMenotti(1987)and Farias-Lariosetal.(1994b). Theresultsreportedthat the great-esttotalyieldofcucumberplantswasobtainedwithtransparent polyethylenemulchfollowedbyblackpolyethyleneandthenby dripirrigationwithoutmulching.Thiseffectwasstatistically sig-nificantinbothseasons.Theunmulchedplotswerehand-weeded fourtimesoverthegrowingseason.Noeffortwasmadeto con-trolweedsinthemulchedplots.Although,clearplasticmulchmay resultinanincreaseinsoiltemperature,thepresenceoflightled tothedisadvantageofweedgrowth,whiletheabsenceoflight withblackplasticdidnotallowphotosynthesisofweedsunderthe filmandthereforeweedgrowthwassuppressed.Thisresultwasin agreementwiththatfoundbyLamont(1999,2001).

4. Conclusions

With growingwater demand and increasing signs of water scarcity,thereisanurgentneedtoachievehigheroutputperunitof waterconsumed.Fortunately,thereisamplescopetoimprovecrop waterproductivity,particularlyinareaswhereyieldsarecurrently

low. In thepresent study, effects of drip irrigation and plastic mulchonwaterappliedandWUEwasinvestigated.Theresultsof thestudyindicatedthatDI+TMandDI+BMtreatmentsmarkedly decreasedwaterappliedintheorderofDI+TM<DI+BM<DI<SI andincreasedWUEintheorderofDI+TM>DI+BM>DI>SI.The DI+TMtreatmentattainedthehighestWUEof0.262tha−1mm−1. The lowest WUE (0.056tha−1mm−1) realized for the SI treat-mentTheseresultsarealsoinagreementwiththoseofJainetal. (2000), who concluded that drip irrigation and plastic mulch markedly affectsappliedwater and wateruseefﬁciency. Refer-ence cropevapotranspiration (ET0)value was calculated based

of Penman–Monteith method, which was recorded the maxi-mumvalueduringJuly.Actualevapotranspiration(ETa)startedto increasefromthedateofsowingtillMidseasonstageandbecame maximuminJulyandAugustthenagainreducedinthelast Matu-rityandharveststageinSeptember.Thecropcoefﬁcient(Kc)values

decreased byanaverageof35% duetousedripirrigationwith mulch.Thepercentofwaterusereductionwas65%,64%and57% forthetransparentmulched dripirrigation,blackmulched drip irrigationandnomulchdripirrigation,respectivelycomparedto thefurrowsurfaceirrigationtreatment.

Resultsalsoindicatedthatplasticmulchgenerallyraisedsoil temperature,whereastransparentplasticmulchraisedthelimits ofthesoiltemperature(6.4,5.9and5.6)◦Crespectivelyatthe sur-faceofsoil,atthe5cmsoildepthandatthe10cmsoildepth.While blackplasticmulchraisedthelimitsofthesoiltemperature(3.1, 2.7and2.4)◦Crespectivelyatthesameprevioussoildepth, com-paredwithboth irrigationtreatments withoutmulching,which enhancedCucumbervegetativegrowthandsignificantlyincreased itsproductivitylimitsof(70%,53%and17%)foralldripirrigation treatments (transparentplastic mulch, black plastic mulch and withoutmulch),comparedtothesurfacefurrowirrigation treat-ment.whereastransparentplasticmulchraisessoiltemperature; however,blackplasticisadvantageousforweedcontrol.Asifthere arebenefitsofplasticmulch,therearealsosomeproblemssuchas removingtheplasticmulchafterthecroppingseasonisthebiggest disadvantage.Littlepiecesofplasticcanscatteracrossafield.Many landfillsalsowillnotacceptplastic,anditisdifficulttorecycle.The costofapplyingplasticmulchcanbequitehighbothintermsof materialsandequipment.Withdripirrigation,managingplastic mulchismoreintense.Wiltingplantscouldmeanapluggeddrip line,whileoverlywetareascouldmeanrodentdamagetothelines. Driplineproblemsarehardtoevaluatewhencoveredwithmulch. Althoughthat,wesuggestpopularizationofthesestudytoinclude othercropsthatmoreprofitforfarmerssuchsquash,pepperand tomato,andhopeuseothermanycolorsofplasticmulchand exam-inationthemeffectonwateruseefficacy(WUE),andPotentialto double-cropplasticmulch(seeWatereretal.,2008).Weadviseuse organicmulchalsosuchasrice,wheatandbarleystrawsanddonot adviceuseofplasticmulchonpotatoeswhichplantedinAutumn seasonbecauseofhighsoiltemperaturesunderplasticmulchwill destroyedpotatonodes(seeWangetal.,2004).

Lastbutnotleast,Dripirrigationsigniﬁcantlyincreasedcrop yieldofCucumberandimprovedWUEduetoconsumptionofless water.However,integrateduseofdripirrigationandplasticmulch wasmoreappropriateandproﬁtable.Therefore,dripirrigationin combinationwithplasticmulchespecially(transparentmulch)was foundtobemoreeffectiveirrigationmethodinimprovingWUEand increasingcropyieldofcucumber.

Acknowledgements

Theauthorsarethankfulforthesupportandencouragementof Prof.M.NayefAlSaltitheDGoftheGeneralCommissionfor Scien-tiﬁcAgriculturalResearchinSyria(GCSAR),thesupportoftheWLI

(8)

(WaterandLivelihoods’Initiative),anUSAIDfundedprojectforthe MiddleEast(Egypt,Iraq,Jordan,Lebanon,Palestine,SyriaYemen). Dr.VinayNangiaandDr.TheibOweis,(ICARDA),Dr.FaroukOdeim (AECS)andDep.ofRuralEngineering,FacultyofAgric.,Aleppo Uni-versity.

References

Allen,G.R.,Pereira,L.S.,Raes,D.,Smith,M.,1998.Cropevapotranspiration,Irrigation andDrainagepaperno.56.FAO,Rome,Italy,pp.300.

Bakker,J.C.,Sonneveld,C.,1988.Calciumdeﬁciencyofglasshousecucumberas affectedbyenvironmentalhumidityandmineralnutrition.Journalof Horti-culturalScience,London63(2),241–246.

Battikhi,A.,Ghawi,I.,1987.Squash(Cucurbitapeople)productionunderMulchand TrickleirrigationintheJordanValley,UniversityofJordan.DirasatXIV(11), 59–72.

Burba,G.G.,Verma,S.B.,2005.Seasonalandinterannualvariabilityin evapotranspi-rationofnativetallgrassprairieandcultivatedwheatecosystems.Agricultural andForestMeteorology135,190–201.

Cantliffe,D.J.,1981.Alterationofsexexpressionincucumberduetochangesin temperature,lightintensity,andphotoperiod.JournaloftheAmericanSociety ofHorticulturalScience,Geneva106(2),133–136.

Castilla,N.,1990.Technologytransferontheuseoflocalizedirrigation.In:Proc.XI Int.Congr.“TheuseofplasticsinAgriculture”,1,NewDelhi,India,pp.33–39.

Darwish,T.,Atallah,T.,Hajhasan,M.,Chranek,S.,2003.Managementofnitrogen byfertigationofpotatoinLebanon.NutrientCyclinginAgroecosystems67, 1–11.

Diaz-Perez,J.C.,Batal,K.D.,2002.Coloredplasticﬁlmmulchesaffecttomatogrowth andyieldviachangesinroot-zonetemperature.JournaloftheAmericanSociety forHorticulturalScience127(1),127–136.

Doss,B.D.,Evans,L.E.,1980.Irrigationmethodsandinrowchiselingfortomato production.JournaloftheAmericanSocietyforHorticulturalScience,105–611.

Drost,D.,Hefelbower,R.,2004.CucumbersintheGardenpracticalsolutionsfora complexworld.UtahStateUniv.,pp.13(2).

El-Nemr,A.M.,2006.Effectofmulchtypesonsoilenvironmentalconditionsand theireffectonthegrowthandyieldofcucumberplants.JournalofApplied SciencesResearch2(2),67–73.

Ertek,A.,Sensoy,S.,Gedik,I.,Küc¸ükyumuk,K.C.,2006.Irrigationschedulingbased cucumber(CucumissativusL.)grownunderﬁeldcondition.AgriculturalWater Management81(1–2),159–172.

FAO,1998.CropEvapotranspiration.IrrigationandDrainagePaper,Rome,56. Farias-Larios,J.M.,Orozco,S.,Guzman,S.,1994a.Soiltemperatureandmoisture

underdifferentplasticmulchesandtheirrelationtogrowthandcucumberyield inatropicalregion.Gartenbauwissenschaft59(6),249–252.

Farias-Larios,J.,Guzman,S.,Michel,A.C.,1994b.Effectofplasticmulchesonthe growthandyieldofcucumberinatropicalregion.BiologicalAgricultureand Horticulture10(4),303–306.

Gajri,P.R.,Arora,V.K.,Chaudhary,M.R.,1994.Maizegrowth,responsetodeeptillage, strawmulchingandfarmyardmanureincoarsetexturedsoilsofN.W.India.Soil UseandManagement10,15–20.

Ghorbani,B.,2003.Evaluationofplasticmulcheffectsoncucumberandtomato yieldsatﬂoweringandproductionstages.In:ProceedingsofTheFourth Inter-nationalIranandRussiaConference,pp.805–809.

Ham,J.M.,Kluitenberg,G.J.,1994.Modelingtheeffectofmulchopticalproperties andmulch-soilcontactresistanceonsoilheatingunderplasticmulchculture. AgricultureforMeteorology71,403–424.

Ham,J.M.,Kluitenberg,G.J.,Lamont,W.J.,1993.Opticalpropertiesofplasticmulches affecttheﬁeldtemperatureregime.JournalofAmericanSocietyofHorticultural Sciences228(2),188–193.

ICARDA,2000.AgriculturalResearchStrengtheningandHumanResource Develop-mentintheArabianPeninsula(1995–2000)FinalReport,18.AFESDandIFAD, pp.87.

Jain,N.,Chauhan,H.S.,Singh,P.K.,Shukla,K.N.,2000.Responseoftomatounder dripirrigationandplasticmulching.In:Proceedingof6thInternational Micro-irrigationCongress,Micro-irrigationTechnologyforDevelopingAgriculture, 22–27October2000,SouthAfrica.

Janat,M.,2003.Effectofdripfertigationonimprovementofpotatoyieldandwater useefﬁciency.In:AECS-A/RRE,126.,pp.1–38.

Jenni,S.,Brault,D.,Stewart,K.A.,2000.DegradableMulchasanalternativeforweed controlinLettuceProducedonorganicsoils.HRDC,AgricultureandAgri-Food Canada,430Boul.Gouin,St-Jean-sur-Richelieu,Quebec,Canada.J3B3E6;Dept. ofPlantScience,MacdonaldCam-PusofMcGillUniv.,Ste-Anne-de-Bellevue, Que,Canada,H9X3V.(9).

Jitan,M.A.,2012.Irrigation managementinformationsystem inJordan, Train-ingCourseonImprovingWaterProductivityinAgriculturalSystems.Amman, Jordan(NCARE)May6thtoMay24th,availableat:www.ncare.gov.jo; MAJi-tan@ncare.gov.jo.

Khurshid,K.,Iqbal,M.,Arif,M.S.,Nawaz,A.,2006.Effectoftillageandmulchonsoil physicalpropertiesandgrowthofmaize.InternationalJournalofAgriculture andBiology(5),593–596.

Kirnak,H.,Demirtas,N.M.,2006.Effectofdifferentmulchesonyieldandmacro nutritionlevelsofdrip–irrigationcucumberviaopenﬁeldconditions.Journal ofPlantNutrition29(9),1675–1690.

Korir,N.,Aguyoh,K.,Gaqiong,J.N.,2006.Enhancedgrowthandyieldofgreenhouse producedcucumberunderhighaltitudeareasofKenya.AgriculturalTropical andSubtropical39(4),249–254.

Lamont,W.J.,2005.Plastics:modifyingthemicroclimatefortheproductionof veg-etablecrops.HortTechnology15,477–481.

Lamont, W.J., 2001. Vegetable Production using Plasticulture. Food and Fer-tilizeTechnologyCenter,Availableat: http://www.agnet.org/library/article/ eb476.html

Lamont,W.J.,1999.Theuseofdifferentcoloredmulchesforyieldandearliness.In: ProceedingsoftheNewEnglandVegetableandBerryGrowersConferenceand TradeShow,Sturbridge,MA,pp.299–302.

Liakatas,A.,Clark,J.A.,Monteith,J.L.,1986.Measurementsoftheheatbalanceunder plasticmulches.PartI.Radiationbalanceandsoilheatﬂux.Agriculturefor Meteorology36,227–239.

Liebig,H.P.,1981.Physiologicalandeconomicalaspectsofcucumbercropdensity. ActaHorticulturae,TheHague118,149–164.

Louise,E.B.,Lassoie,J.P.,Fernandez,E.M.,1999.AgroForestryinSustainable Agri-culturalSystems.CRCPress,BocaRaton/NewYork/Washington,DC,pp.53–56.

Marcelis, L.F.M.,Baan Hofman-Eijer, L.R., 1993. Effect oftemperature onthe growthofindividualcucumberfruits.PhysiologiaPlantarum,Kobenhavn87(3), 321–328.

Mata,V.H.,Nunez,E.R.,Sanchez,G.P.,2002.Soiltemperatureandsoilmoisturein Ser-ranopepper(CapsicumannuumL.)withfertigationandmulching.In:Proceeding ofthe16thInternationalPepperConference,Tamaulipas,Mexico,Available at: http://www.pepperconference.org/proceedings/soiltemperatureandsoil

moisture.pdf

Medany,M.A.,Wadid,M.M.,Abou-Hadid,A.F.,1999.Cucumberfruitgrowthratein relationtoclimate.ActaHorticulturae,TheHague486,107–111.

Mustafa,O.S.,Arshad,I.M.,Sattar,S.A.,2003.Adoptionofkostiakofmodelto deter-minethesoilinﬁltrationforsurfaceirrigationmethodsunderlocalconditions. InternationalJournalofAgricultureandBiology1,40–42.

Ngouajio,M.,Ernest,J.,2005.Changesinthephysical,optical,andthermalproperties ofpolyethylenemulchesduringdoublecropping.Hortscience40,94–97.

Ngouajio,M.,Wanga,G.,Goldy,R.,2006.Withholdingofdripirrigationbetween transplantingandﬂoweringincreasestheyieldofﬁeld-growntomatounder plasticmulch.AgriculturalWaterManagement87(3),285–291,Availableat: ScienceDirect.

Orzolek,M.D.,2000.NewConceptsinPlasticultureforTomatoesandPeppers814. ThePennsylvaniaStateUniversity,UniversityPark,PA,pp.863–1150.

Orzolek,M.D.,Murphyj,J.,Giardi,2003.Theeffectofcoloredpolyethylenemulchon theyieldofsquash.In:TomatoandCauliﬂowerCollegeofAgriculturalSciences. PennStateUniversity.

Oweis,D.,2012.On-farmWaterManagement:fromefﬁciencytoproductivity. In:TrainingCourseonImprovingWaterProductivityinAgriculturalSystems, Amman,Jordan(NCARE)May6thtoMay24th,IWLMP-ICARDA.

Patel,J.C.,Patel,B.K.,2001.Responseofpotatotonitrogenunderdripandfurrow methodsofirrigationIndia.JournaloftheIndianPotatoAssociation28(4), 293–295.

Pawar,D.D.,Bhoi,P.G.,Shinde,S.H.,2002.Effectofirrigationmethodsandfertilizer levelsonyieldofpotato(Solanumtuberosum).IndianJournalofAgricultural Sciences72(2),80–83.

Safadi,A.S.,1991.Squashandcucumberyieldandwaterusemodels.Dept.Biological andIrrigationEngineering,UtahStateUniv.,Logan,UT,pp.190(Unpublished Ph.D.Dissertation).

Saif,U.,Maqsood,M.,Farooq,M.,Hussain,S.,Habib,A.,2003. Effectof plant-ing patternsand differentirrigation levelsonyieldand yieldcomponent ofmaize(Zeamays,L.).InternationalJournalofAgricultureandBiology1, 64–66.

Salman,S.R.,Abou-Hadid,A.F.,El-Beltagy,A.S.,El-Labban,T.T.,1991a.The interrela-tionbetweenplasticmulchandirrigation.EgyptianJournalofHorticulture18 (1),77–86,publ.1993.

Samuel,J.C.,Singh,H.P.,2003.Plasticultureinterventionsforhorticulture develop-mentinIndiaanditssigniﬁcanceinnorth-easternregion.In:Region-Satapathy, K.,Ashwani,K.(Eds.),PlasticcultureInterventionforAgricultureDevelopment inNorthEastern.ICARResearchComplexforNEHRegion,Umiam,Meghalaya, pp.31–42.

Seyﬁ,K.,Rashidi,M.,2007.Effectofdripirrigationandplasticmulchoncropyield andyieldcomponentsofCantaloupe.InternationalJournalofAgricultureand Biology9(2),247–249.

Simms,T., Bantle,J.,Hrycan, W.,Waterer,D.,2005. Potentialto DoubleCrop Cucumbers and Peppers on Plastic Mulch. Department of Plant Sciences UniversityofSaskatchewan,Saskatoon,Saskatchewan,Canada,Availableat:

http://www.usask.ca/agriculture/plantsci/vegetable

Simonne,E.H.,Dukes,M.D.,2010.PrinciplesandPracticesofIrrigation Manage-mentforVegetables.UF,UniversityofFlorida,HorticultureScienceDept,IFAS Extension,pp.17–23.

Sivanappan,R.K.,Rajgopal,A.,Paliniswami,D.,1974.Responseofvegetabletothe dripirrigation.MadrasAgriculturalJournal65,576–579.

Steyn,J.M.,Plessis,H.F.,Fourier,P.,Roos,T.,2000.Irrigationschedulingofdrip irri-gatedpotatoes.In:Proceedingof6thInternationalMicro-irrigationCongress, Micro-irrigationTechnologyforDevelopingAgriculture,SouthAfrica,22–27 October.

Tarara,J.M.,2000.MicroclimatemodiﬁcationwithplasticMulch.Hortscience3(5), 169–180.

Tiwari,K.N.,Singh,A.,Mal,P.K.,2002.Effectofdripirrigationonyieldof cab-bage(BrassicaoleraceaL.var.capitata)undermulchandnon-mulchconditions.

(9)

PlasticultureDevelopmentCentre,AgriculturalandFoodEngineering Depart-ment,IndianInstituteofTechnology,Kharagpur721302,WestBengal,India. AgriculturalWaterManagement58(1),19–28.

Vickers,A.,2001.WateruseConservation.WaterPlowPress,Amherst,MA,US,pp. 215–380.

Wang,F.X.,Kang,Y.H.,Liu,S.P.,2006.Effectsofdripirrigationfrequencyonsoil wettingpatternandpotatogrowthinNorthChinaPlain.AgriculturalWater Management79,248–264.

Wang,F.X.,Kang,Y.H.,Liu,S.P.,2004.PlasticMulchingeffectsonpotatounderdrip irrigationandfurrowirrigation.ChineseJournalofEco-Agriculture.

Waterer,D.R.,2000.Effectofsoilmulchesandherbicidesonproductioneconomics ofwarm-seasonvegetablecropsinacoolclimate.HortTechnology10,154–159.

Waterer,D.R.,1999.Inﬂuenceofsoilmulchesandmethodcropestablishmenton growthandyieldsofpumpkin.CanadianJournalofPlantScience80,385–388.

Waterer,D.,Hrycan,W.,Simms,T.,2008.Potentialtodouble-cropplasticmulch. CanadianJournalofPlantScience88,187–193.

Weber,C.,2000.Biodegradablefoilmulchforpicklingcucumbers.GemuseMunchen 36(4),30–32.

Wien, H.C., Menotti, P.L.,1987. Growth, yield, andnutrient uptakeof trans-planted fresh-market tomatoes as affected by plastic mulch and initial nitrogenrate.JournaloftheAmericanSocietyforHorticulturalScience112, 759–763.

Wien,H.C.,Minotti,P.L.,Grubinger,V.P.,1993.Polyethylenemulchstimulatesearly rootgrowthandnutrientuptakeoftransplantedtomatoes.Journalofthe Amer-icanSocietyforHorticulturalScience118(2),207–211.

Zaman,W.U.,Arshad,M.,Saleem,A.,2001.Distributionofnitratenitrogeninthesoil proﬁleunderdifferentirrigationmethods.InternationalJournalofAgriculture andBiology2,208–209.

Zotarelli,L.,Scholberg,J.M.,Dukes,M.D.,Munoz-Carpena,R.,Icerman,J.,2009.

Tomatoyield,biomassaccumulation,rootdistributionandirrigationwateruse efﬁciencyonasandysoil,asaffectedbynitrogenratandirrigationscheduling. AgriculturalWaterManagement96(1),23–34.