Das et al.
theyȱ interactȱ inȱ severalȱ waysȱ (Aulakhȱ et al. 2000,ȱ numberȱofȱworkersȱdueȱtoȱapplicationȱofȱpesticidesȱ
2001a,ȱ2001b).ȱItȱisȱthereforeȱnecessaryȱtoȱunderstandȱ inȱsoil.ȱMicroorganismsȱresponsibleȱforȱnitrificationȱ
allȱ theȱ processesȱ involvedȱ inȱ totalityȱ toȱ getȱ aȱ clearȱ areȱsometimesȱadverselyȱaffectedȱquiteȱinterestinglyȱ
pictureȱofȱNȱtransformationȱinȱsoil.
enough;ȱhowever,ȱammonificationȱisȱoftenȱbenefitedȱ
Mineralizationȱ ofȱ Nȱ inȱ soilȱ variesȱ dueȱ toȱ variousȱ
byȱpesticides’ȱuseȱ(Edwardȱ1966;ȱOkamotoȱ et al. 1999).ȱ
factorsȱlikeȱsoilȱcharacteristics,ȱdifferentȱmanagementȱ
Limitedȱinformationȱisȱavailableȱregardingȱtheȱeffectȱ
practices,ȱ climate,ȱ croppingȱ etc.ȱ Asȱ itȱ isȱ nowȱ wellȱ
ofȱpesticidesȱonȱdistributionȱofȱdifferentȱfractionsȱofȱ
establishedȱ thatȱ nativeȱ soilȱ Nȱ transformationȱ isȱ
inorganicȱandȱorganicȱNȱinȱsoils.
differentȱfromȱthatȱofȱfertilizerȱN,ȱitȱisȱnecessaryȱtoȱ Moistureȱ isȱ anȱ importantȱ factorȱ forȱ theȱ growthȱ
understandȱ theȱ Nȱ transformationȱ process,ȱ whichȱ ofȱ microorganismsȱ andȱ inȱ controllingȱ theȱ rateȱ ofȱ
ultimatelyȱinfluenceȱtheȱNȱuptakeȱbyȱplants.
organicȱ matterȱ decomposition.ȱ Althoughȱ presenceȱ
Ourȱknowledgeȱonȱtheȱinterchangeȱofȱinorganicȱandȱ
ofȱ moistureȱ aboveȱ aȱ certainȱ levelȱ isȱ notȱ congenialȱ
organicȱNȱinȱsoilȱwasȱmostlyȱobtainedȱfromȱstudiesȱ
forȱmicrobialȱactivityȱ(Chenȱ et al. 2012)ȱindirectlyȱitȱ
thatȱ measureȱ onlyȱ theȱ netȱ resultȱ ofȱ twoȱ oppositeȱ
isȱ important,ȱ becauseȱ higherȱ theȱ moistureȱ presentȱ
forces,ȱ namelyȱ immobilizationȱ andȱ mineralization.ȱ
inȱ soilȱ lesserȱ theȱ oxygenȱ availableȱ forȱ microbialȱ
Butȱveryȱfewȱattemptsȱhaveȱsoȱfarȱbeenȱmadeȱtoȱrelateȱ
growth.ȱ Standfordȱ andȱ Epsteinȱ (1974)ȱ reportedȱ aȱ
mineralizationȱofȱNȱwithȱsimultaneousȱdecreaseȱofȱ
nearȱ linearȱ relationshipȱ betweenȱ Nȱ mineralizationȱ
differentȱformsȱofȱorganicȱNȱpresentȱinȱtheȱsoilȱunderȱ
andȱsoilȱwaterȱcontentȱinȱtheȱrangeȱofȱ1/3ȱtoȱ15ȱbar.ȱ
differentȱmicroȱenvironmentalȱconditions.
Theȱpresentȱinvestigationȱwas,ȱtherefore,ȱconductedȱ
toȱstudyȱtheȱchangesȱofȱdifferentȱformsȱorȱinorganicȱ
Pesticidesȱplayȱaȱvitalȱroleȱonȱdifferentȱprocessesȱofȱ andȱ organicȱ Nȱ inȱ soilȱ treatedȱ withȱ pesticidesȱ ofȱ
N-transformationȱinȱsoils.ȱTheȱdegradedȱproductsȱofȱ differentȱ biodegradabilityȱ andȱ maintainedȱ underȱ
pesticidesȱasȱwellȱasȱpersistenceȱofȱpesticidesȱinȱsoilȱ differentȱmoistureȱregimes.
mayȱinfluenceȱdifferentȱN-transformationȱprocessesȱ
occurringȱinȱsoilsȱinȱdifferentȱways.ȱSometimesȱtheȱ Materials and Methods
effectȱ ofȱ pesticidesȱ isȱ injuriousȱ toȱ certainȱ groupȱ ofȱ
Aȱ compositeȱ soilȱ sampleȱ wasȱ collectedȱ fromȱ aȱ
organismsȱ whichȱ inȱ turnȱ isȱ beneficialȱ toȱ others.ȱ
cultivatedȱfieldȱ(0ȱ-15ȱcmȱdepth)ȱofȱaȱdominantȱsoilȱ
Microorganismsȱ responsibleȱ forȱ nitrificationȱ isȱ
seriesȱ ofȱ Chakdahaȱ inȱ theȱ districtȱ ofȱ Nadia,ȱ Westȱ
sometimesȱ adverselyȱ affected,ȱ quiteȱ interestinglyȱ
Bengal.ȱTheȱsoilsȱwereȱairȱdriedȱgroundȱandȱpassedȱ
enough,ȱhowever,ȱammonificationȱisȱoftenȱbenefitedȱ
throughȱ 0.5ȱ mm.ȱ sieve.ȱ Theȱ relevantȱ physicalȱ andȱ
byȱpesticides’ȱuse.ȱPesticides’ȱuseȱtoȱprotectȱstandingȱ
chemicalȱcharacteristicsȱofȱtheȱsoilȱareȱpresentedȱinȱ
cropȱ isȱ nowȱ aȱ regularȱ practiceȱ toȱ farmers.ȱ Soilȱ
Tableȱ1.
applicationȱofȱpesticidesȱcausesȱanȱaccumulationȱofȱ
theȱ degradedȱ productsȱ inȱ topȱ soilȱ (Elimacheȱ et al.
Eachȱofȱ10gȱairȱdriedȱsoilȱwasȱtakenȱinȱ100ȱmlȱbeakerȱ
2012),ȱtheȱsphereȱofȱmaximumȱmicrobialȱactivities.ȱ forȱ theȱ experimentationȱ purpose.ȱ Twoȱ dosesȱ ofȱ
However,ȱconflictingȱreportsȱ(Gaurȱ1990;ȱMoormanȱ Chlorinatedȱ hydrocarbonȱ pesticideȱ (Endosulfan)ȱ
1989;ȱ Paulȱ et al. 2010;ȱ Singhȱ andȱ Prasadȱ 1991)ȱ areȱ andȱ Organophosphorusȱ pesticideȱ (Chlorpyriphos)ȱ
availableȱregardingȱtheȱeffectȱofȱpesticideȱonȱmicrobialȱ atȱ0.5ȱkgȱa.i.ȱha -1 ȱandȱ1ȱkgȱa.i.ȱha -1 ,ȱrespectivelyȱandȱ
activitiesȱ inȱ soils.ȱ Differentȱ Nȱ transformationȱ twoȱ levelsȱ ofȱ moistureȱ viz.ȱ 60%ȱ ofȱ theȱ Moistureȱ
processesȱ areȱ influencedȱ dueȱ toȱ soilȱ applicationȱ holdingȱcapacityȱ(MHC)ȱofȱtheȱsoilȱandȱwaterloggedȱ
ofȱ pesticidesȱ (Syversenȱ andȱ Haarstadȱ 2005).ȱ Bothȱ conditionȱ wereȱ maintainedȱ forȱ incubationȱ study.ȱ
negativeȱ(PrabhuȱandȱRautȱ2011;ȱKarȱ1990;ȱMartinez-
N-treatmentȱ wasȱ includedȱ inȱ theȱ studyȱ atȱ 100ȱ mgȱ
Toledoȱ et al. 1992;ȱMeghrajȱ et al. 1988)ȱandȱpositiveȱ Nȱkg -1 ȱthroughȱ(NH 4 ) 2 SO 4ȱ .ȱAllȱtheȱtreatmentsȱwereȱ
(Balangerȱ et al. 1985;ȱJanaȱ et al. 1987;ȱKucukȱ et al. 2012)ȱ replicatedȱthrice.
responseȱ onȱ biologicalȱ Nȱ fixationȱ areȱ reportedȱ byȱ
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