Kumari et al.

andȱcanȱbeȱgrownȱinȱaȱvariedȱrangeȱofȱagroȱclimaticȱ theȱtemperatureȱandȱorganicȱsubstancesȱinȱtheȱsoilȱ

conditions.ȱ Severeȱ infestationȱ ofȱ weedsȱ formsȱ aȱ (Savage1977,ȱMoormanȱandȱHarperȱ1989).ȱMetribuzinȱ

negativeȱ factorȱ inȱ potatoȱ cropȱ productionȱ becauseȱ isȱweaklyȱbasicȱwhichȱisȱprotonatedȱinȱacidicȱsoil,ȱandȱ

theyȱcompeteȱwithȱcropȱforȱspace,ȱwaterȱandȱnutrientsȱ adsorbedȱbyȱnegativeȱchargesȱofȱcolloidsȱinȱtheȱsoil,ȱ

andȱisȱresponsibleȱforȱmarkedȱlossesȱinȱcropȱyield.ȱ decreasingȱasȱaȱconsequenceȱofȱitsȱconcentrationȱinȱ

Weedȱ lossesȱ areȱ moreȱ seriousȱ becauseȱ fastȱ earlyȱ theȱsoilȱsolution.ȱThisȱmeansȱitȱisȱpositivelyȱcorrelatedȱ

growthȱofȱpotatoȱisȱessentialȱforȱhighȱyield.ȱTheȱyieldȱ withȱsoilȱpHȱ(Weberȱ et al. 1993).ȱSlowȱdegradationȱofȱ

reductionȱdueȱtoȱweedsȱinȱpotatoȱisȱestimatedȱtoȱbeȱ metribuzinȱ inȱ subsurfaceȱ horizonȱ soilȱ isȱ attributedȱ

asȱhighȱasȱ10ȱtoȱ80%ȱ(LalȱandȱGuptaȱ1994,ȱKumarȱ et al.

toȱ inherentlyȱ lowerȱ microbialȱ activityȱ (Lockeȱ andȱ

2007,ȱ2008).ȱInȱweedȱmanagementȱpractices,ȱchemicalȱ Harperȱ1991,Lockeȱ1992).ȱHowever,ȱXuȱ et al. (2000)ȱ

weedȱ controlȱ holdsȱ aȱ greatȱ promiseȱ inȱ dealingȱ reportedȱ rapidȱ dissipationȱ ofȱ metribuzinȱ inȱ sandyȱ

withȱ effectiveȱ andȱ economicȱ weedȱ suppression.ȱ loamȱduringȱtheȱinitialȱ10–15ȱdaysȱandȱconcludedȱthatȱ

Thoughȱ chemicalȱ weedȱ controlȱ contributeȱ gainfulȱ leachingȱmightȱbeȱanȱimportantȱdissipationȱpathwayȱ

incrementȱinȱcropȱproduction,ȱyetȱitȱisȱimportantȱtoȱ forȱ metribuzinȱ underȱ irrigatedȱ potatoȱ production.ȱ

makeȱproperȱuseȱofȱherbicides.ȱTheȱmostȱimportantȱ SimilarȱresultsȱareȱalsoȱgivenȱbyȱKhouryȱ et al. (2003)ȱ

considerationȱinȱchemicalȱweedȱcontrolȱisȱpersistenceȱ whoȱfoundȱveryȱintenseȱandȱrapidȱdegradationȱandȱ

ofȱherbicideȱinȱsoil,ȱandȱitsȱresidueȱinȱcropȱproduce.ȱ highȱmobilityȱofȱmetribuzinȱinȱsandyȱloamȱandȱclayȱ

Theȱ persistenceȱ ofȱ pesticideȱ inȱ theȱ soilȱ determinesȱ soils.ȱTheȱpersistenceȱofȱherbicideȱinȱsoilȱisȱtheȱresultȱ

periodȱofȱtimeȱforȱwhichȱitȱremainsȱactive.ȱInȱcaseȱ ofȱ interactionȱ ofȱ edaphicȱ andȱ climaticȱ factorsȱ withȱ

ofȱ herbicides,ȱ persistenceȱ isȱ particularlyȱ importantȱ herbicide.ȱHerbicideȱresidueȱestimationȱinȱsoilȱandȱ

becauseȱonȱoneȱhandȱitȱdeterminesȱtheȱperiodȱofȱtimeȱ edibleȱpartsȱisȱveryȱessentialȱtoȱdetermineȱherbicideȱ

forȱwhichȱweedsȱcanȱbeȱcontrolledȱandȱonȱtheȱotherȱ activityȱinȱsoilȱandȱitsȱeffectȱonȱcropȱqualityȱ.Fieldȱ

hand,ȱitȱisȱrelatedȱtoȱtheȱphytotoxicȱeffectsȱwhichȱcanȱ studiesȱ onȱ persistenceȱ ofȱ metribuzinȱ residuesȱ inȱ

damageȱtheȱsubsequentȱcropȱ(ȱWeberȱ1993,ȱLiuȱ et al.

potatoȱcropȱinȱNorthȱwesternȱHimalayanȱregionȱareȱ

2005).

veryȱ meager.ȱ Theȱ presentȱ studyȱ wasȱ undertakenȱ

Metribuzinȱ [4-amino-6-(1,ȱ 1-dimethylethyl)-3-

withȱ theȱ objectiveȱ toȱ determineȱ persistenceȱ ofȱ theȱ

(methylthio)-2,ȱ 5-triazin-5-(4H)-one],ȱ aȱ triazineȱ

metribuzinȱresiduesȱinȱsoilȱandȱbioaccumulationȱinȱ

herbicideȱ isȱ recommendedȱ asȱ bothȱ pre-emergenceȱ

potatoȱcrop.

andȱ earlyȱ post-emergenceȱ toȱ controlȱ ofȱ broadȱ

Materials and Methods

spectrumȱ ofȱ weedȱ floraȱ inȱ fieldȱ andȱ vegetableȱ

cropsȱ includingȱ potatoesȱ (Majumdarȱ andȱ Singhȱ

Reagents and chemicals

2007,ȱKhouryȱ et al. 2006).ȱTheȱsiteȱofȱactionȱofȱthisȱ

groupȱ ofȱ herbicideȱ isȱ PSIIȱ ofȱ photosynthesisȱ andȱ

Metribuzinȱ(99.8%)ȱwasȱobtainedȱfromȱAccuStandard,ȱ

interferesȱ withȱ photosyntheticȱ electronȱ transportȱ

Inc.,USAȱ andȱ purityȱ checkedȱ byȱ GCȱ beforeȱ use.ȱ

betweenȱ primaryȱ andȱ secondaryȱ acceptorsȱ ofȱ

Formulationȱ ofȱ metribuzinȱ (Sencorȱ 70%ȱ WP)ȱ wasȱ

photosystemȱ II.ȱ Itȱ isȱ readilyȱ takenȱ upȱ byȱ theȱ rootsȱ

purchasedȱfromȱlocalȱmarket.ȱTheȱsolventsȱusedȱinȱ

andȱtranslocatedȱtoȱtheȱshootsȱandȱleavesȱofȱtreatedȱ

studyȱwereȱofȱanalyticalȱgradeȱandȱpurchasedȱfromȱ

plantsȱ inȱ theȱ apoplastȱ (Walkerȱ et al. 1996,ȱ Sondhiaȱ

MerckȱIndiaȱPvt.ȱLtd.

2005).ȱSoilsȱrepresentȱaȱcomplexȱbiological,ȱchemicalȱ

Field experiment

andȱ physicalȱ media.ȱ Differentȱ studiesȱ conductedȱ

toȱevaluateȱtheȱdegradationȱofȱmetribuzinȱreportedȱ Fieldȱexperimentȱusingȱaȱrandomizedȱblockȱdesignȱ

thatȱmostȱofȱdegradationȱofȱmetribuzinȱoccurredȱasȱ withȱfourȱreplicationsȱpertainingȱtoȱtheȱresiduesȱofȱ

aȱ resultȱ ofȱ aerobicȱ microbialȱ activityȱ andȱ followedȱ metribuzinȱinȱsoilȱandȱpotatoȱtuberȱwasȱconductedȱ

pseudoȱ first-orderȱ kinetics,ȱ andȱ wasȱ influencedȱ byȱ atȱtheȱResearchȱFarmȱofȱDepartmentȱofȱAgronomy,ȱ

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