JuneandJuly2016
GrowthandNitrogenLossesofWarm-SeasonTurfgrassesIrrigatedwithTailored
WaterDuringEstablishment
JanicePalmer
Mentor:Dr.ElenaSevostianova
Professor:Dr.BerndLeinauer
Turfgrassisthemostwidelygrown‘crop’intheUnitedStates,coveringapproximately3timesasmuchareaas
thenextleadingcrop.1Anyenvironmentalconsequencesofgrowingturfgrasscanthereforehaveamajoreffectdueto
thesheerareacovered.Twoprimaryconcernswithturfgrassarethatitusesalargevolumeofwaterandthatnitrogen
fromfertilizercancontaminatetheenvironment.Nitratescanleachintogroundwater(causinghealthproblems)and
runoffintolakesandrivers(promotingalgaegrowth).Nitrousoxide,apotentgreenhousegas,mayalsobeproduced.
Itisthereforeveryimportanttoadoptstrategiestoconservepotablewaterandminimizeenvironmentalconsequences
whengrowingturfgrass.
Commonturfmanagementincludesspreadinggranularnitratefertilizerandirrigatingwithpotablewater.The
purposeofthisexperimentwastodetermineifusingtailoredwaterinsteadisaneffectivetreatmentforwarm-season
turfgrassesduringestablishment.Tailoredwaterconsistsoftreatedwastewaterwithanitrateconcentrationof
approximately15ppm,higherthanthemaximumconcentrationinpotablewaterof10ppm2.Theuseoftailoredwater
wouldhelpconservepotablewaterresources.Thesetwoirrigationwaterqualitieswerecomparedtoinvestigatethe
effectsongrowthandnitrogenmovement.Wehypothesizedthatthegrassirrigatedwithtailoredwaterwould
establishnoworsethanandhavenogreaternitrogenlossesthanthegrassirrigatedwithpotablewaterandfertilized
withgranularfertilizer.
Thisexperimentwasperformedinagreenhouseusingthreetypesofwarm-seasonturfgrasses:bermudagrass
[Cynodondactylon(L.)]cv.‘Princess77’],buffalograss[Buchloedactyloides(Natt.)Engl.cv.‘SWI2000’],andinland
saltgrass[Distichlisspicata(L.)].Thegrasswasgrownineighteen5-galloncontainerswhichwereplacedrandomly
throughoutthegreenhouse.Therewerethreereplicationsofeachtreatment.Thepotabletreatmentcontainerswere
fertilizedwithgranularcalciumnitratefertilizereverytwoweeksandwateredonceaday.Thetailoredtreatment
containerswerewateredonceadaywiththesamevolumeofwater.Thewatervolumewasdeterminedbymeasuring
climateconditionsinthegreenhouseandcalculatingevapotranspirationrates.
Avarietyofsamplesandmeasurementsweretakentocompareestablishmentandnitrogenmovementinthe
turfgrasssystems.Toassessestablishment,digitalimageanalysiswasperformedusingSigmaScantodeterminepercent
coverage.Thisinformationwasusedtomeasurelateralgrowthdifferencesanddeterminewhenestablishmentwas
completed.Additionally,thegrasswas‘mowed’onceaweekandclippingswerecollected.Theclippingswereplacedin
anoventodryfortwodaysandthenweighed.Onesetofclippingswasalsotestedfornitrogencontent.Thetotalmass
ofclippings,alongwiththenitrogendata,willprovideinformationaboutverticalgrowthpatternsandtheamountof
nitrogenleavingthesystemviatheclippings.
Leachatesampleswerealsocollectedtotracknitrogenleavingthesystemsviadrainages.Drainagewaterwas
gatheredintraysunderneatheachcontainer.Watersampleswerealsotakenusinglysimetersatadepthof10cm.The
watersampleswereallanalyzedforelectricalconductivity,pH,andnitratelevels.Thevolumeofdrainagewas
recorded.
Onceaweek,gassamplingwasperformedtodeterminenitrousoxideemissions.Gaschamberswereplacedon
eachcontainerandVacutainerswereusedtostoregassamplescollectedat0,20,and40minutesaftersealing.Airand
soiltemperaturesweremeasuredconcurrently.Thesampleswereanalyzedusingagaschromatograph-electron
capturedetectortodeterminetheconcentrationofnitrousoxideemittedfromthegrasscontainer.
Rootsampleswerealsotakentodeterminediameteranddensityofroots.Thisinformationwillbeusedto
analyzehowrootstructuremayaffectnitrateleaching.
PreliminaryResults
Figure1showsthecoverageofgrasses
overtime.Itappearedthatfor
bermudagrassandsaltgrass,coverage
growthwassimilarregardlessof
treatment,whileforbuffalograss,the
potablewaterresultedinincreased
coverage.
Resultsfromtheweeklyclippings
showedthatinthecasesof
Figure1:CoverageofGrassesOverTime
bermudagrassandbuffalograss,biomass
wassignificantlygreaterforthepotable
watertreatment.Saltgrasswastheopposite,withagreaterbiomassforthetailoredwatertreatment.Onefactorto
noteisthatthesaltgrassestablishmentwasveryslow,whichresultedinsparsecoverage.Thismayhavebeenaresult
ofunviableseeds.
Therewasinsufficientdrainagetorunastatisticalanalysisonnitrateconcentrationsorelectricalconductivityinthe
watersamples.Despitenothavingthoseresults,thelackofdrainagewasausefulresultinthatitshowedthatif
turfgrassiscarefullywateredbasedonevapotranspiration,therewillbeminimalornodrainageandthereforeminimal
ornonitrateleachingintogroundwater.
Preliminarydatafornitrousoxideshowedthatnitrousoxidelevelsweretypicallyaroundambientlevel(inthe.3ppm
range).However,moreresearchisneededtodeterminethesystem’saccuracyatoraroundambientlevels.Atthis
stage,thedataseemstoindicatethatnitrousoxideisnotproducedinsignificantamountsbyturfgrasssystemsirrigated
witheithertailoredorpotablewater.
Overall,preliminaryresultsshowthatpotablewaterplusgranularfertilizerpromotesverticalgrowthinwarm-season
turfgrassesbetterthantailoredwater.Lateralgrowth,asshownbycoverage,seemstovarydependingontypeof
turfgrassandfertilizer.Italsoappearsthatnitrousoxideemissionsfromturfgrasssystemsareverylow.Itwasfound
thatwateringbasedonevapotranspirationresultsinminimalnitrateleachingoutofthesystem.Thisexperimentwillbe
continuingforapproximatelytwomoreweeksandattheendofthatperiodfinalresultswillbereported.
References
1
Milesi,C.,Elvidge,C.D.,Dietz,J.B.,Tuttle,B.T.,Nemani,R.R.,&Running,S.W.(n.d.).AStrategyforMappingand
ModelingtheEcologicalEffectsofUSLawns.ISPRSJournalofPhotogrammetryandRemoteSensing.RetrievedJuly27,
2016.
2
NationalPrimaryDrinkingWaterRegulations.(2009,May).RetrievedJuly28,2016,fromhttps://www.epa.gov/groundwater-and-drinking-water/national-primary-drinking-water-regulation-table