Distribution and Availability of Sulphur in some Terai Soils under Subtropical Zone of Eastern India
andȱ containedȱ relativeȱ lessȱ totalȱ Sȱ asȱ comparedȱ toȱ Adsorbed sulphur
others.ȱTheȱoverallȱvariationsȱofȱmeanȱtotalȱsulphurȱ
Adsorbedȱ formȱ ofȱ sulphurȱ wasȱ foundȱ toȱ maintainȱ
statusȱ inȱ surfaceȱ layerȱ ofȱ soilsȱ amongȱ theȱ districtsȱ
highȱvariationsȱwithinȱtheȱrangeȱfromȱ1.20ȱtoȱ52.09ȱmgȱ
mayȱbeȱascribedȱmainlyȱtoȱtheȱdifferencesȱinȱorganicȱ
kg -1 ȱsoilȱwithȱaȱmeanȱvalueȱofȱ17.94ȱmgȱkg -1 ȱsoilȱ(Tableȱ
matterȱcontentȱasȱinfluencedȱbyȱnatureȱandȱintensityȱ
4).ȱ Thisȱ formȱ ofȱ sulphurȱ comprisingȱ theȱ smallestȱ
ofȱcropping,ȱsoilȱandȱfertilizerȱmanagementȱpracticesȱ
fractionȱofȱtheȱtotalȱSȱaccountedȱforȱ0.23ȱtoȱ9.82ȱperȱ
followedȱandȱwaterȱuseȱandȱdrainageȱsystemȱ(Patelȱ et
centȱwithȱaȱmeanȱofȱ5.8ȱperȱcentȱofȱtotalȱSȱ(Figureȱ1).ȱ
al. 2011;ȱIsitekhaleȱ et al. 2013).
TheȱhighestȱamountȱofȱadsorbedȱSȱobtainedȱinȱtheȱ
Organic sulphur
particularȱ soilȱ sampleȱ belongingȱ underȱ Binnaguriȱ
seriesȱmightȱhaveȱbeenȱdueȱtoȱtheȱpresenceȱofȱveryȱ
Organicȱ sulphurȱ wasȱ shownȱ toȱ maintainȱ aȱ highȱ highȱ totalȱ S,ȱ organicȱ Sȱ andȱ organicȱ matterȱ contentȱ
variabilityȱ inȱ theȱ rangeȱ fromȱ 157.07ȱ toȱ 450.92ȱ mgȱ ((Isitekhaleȱ et al. ȱ 2013)ȱ alongȱ withȱ presenceȱ ofȱ
kg -1 ȱ withȱ anȱ averageȱ valueȱ ofȱ 272.05ȱ mgȱ kg -1 ȱ soilȱ notablyȱ higherȱAlȱ andȱ Feȱ oxidesȱ (Basumataryȱ andȱ
(Tableȱ4),ȱwhichȱaccountedȱforȱ29.62ȱtoȱ85.02ȱperȱcentȱ Das,ȱ2012)ȱasȱcomparedȱtoȱthoseȱinȱotherȱlocationsȱ
ofȱtotalȱsulphurȱofȱtheȱsoilȱsamplesȱwithȱaȱmeanȱofȱ whichȱ collectivelyȱ contributedȱ toȱ higherȱ retentionȱ
88ȱperȱcentȱ(Figureȱ1).ȱItȱwasȱrevealedȱthatȱsamplesȱ ofȱ sulphateȱ Sȱ onȱ adsorptiveȱ sites.ȱ Adsorbedȱ Sȱ
fromȱRajpurȱseriesȱofȱCoochBeharȱdistrictȱcontainedȱ statusȱwhenȱcomparedȱamongstȱtheȱsoilȱseriesȱandȱ
relativelyȱ lessȱ amountȱ ofȱ organicȱ sulphurȱ withȱ aȱ benchmarkȱ sites,ȱ itȱ wasȱ observedȱ thatȱ majorityȱ ofȱ
meanȱ ofȱ 204.50ȱ mgȱ kg -1 ,ȱ beingȱ theȱ lowestȱ amongȱ soilȱ samplesȱ fromȱ Binnaguriȱ seriesȱ ofȱ Jalpaiguriȱ
allȱ theȱ locationsȱ studied.ȱ Whileȱ soilȱ samplesȱ fromȱ districtȱ retainedȱ veryȱ highȱ amountsȱ ofȱ sulphateȱ Sȱ
Kharibariȱ benchmarkȱ siteȱ inȱ plainsȱ ofȱ Darjeelingȱ inȱadsorbedȱformȱasȱcomparedȱtoȱthoseȱrecordedȱinȱ
districtȱwasȱshownȱtoȱbeȱrelativelyȱhigherȱinȱorganicȱ anyȱotherȱlocations;ȱtheȱmeanȱconcentrationȱofȱwhichȱ
sulphurȱstatusȱwithȱmeanȱorganicȱsulphurȱcontentȱofȱ beingȱ withȱ 32.01ȱ mgȱ kg -1 ȱ soilȱ wasȱ regardedȱ asȱ theȱ
319.15ȱmgȱkg -1 ȱsoil,ȱbeingȱtheȱhighestȱamongȱallȱtheȱ highestȱvalueȱamongstȱtheȱallȱlocations.
locations.ȱOrganicȱSȱinȱsoilsȱalsoȱfoundȱtoȱfollowȱaȱ
similarȱtrendȱtoȱthatȱofȱtotalȱSȱwhenȱitsȱinter-districtȱ Heat soluble sulphur
variationsȱwereȱconsidered.ȱOrganicȱSȱformedȱlargestȱ
ThisȱformȱofȱS,ȱwhichȱindicatesȱtheȱmineralizableȱSȱ
fractionȱ ofȱ totalȱ Sȱ inȱ theȱ soilsȱ andȱ hadȱ significantȱ
variedȱ(Tableȱ4)ȱinȱsoilȱsamplesȱfromȱ31.67ȱtoȱ93.27ȱ
positiveȱrelationshipȱwithȱtotalȱS,ȱorganicȱcarbonȱandȱ
withȱ aȱ meanȱ valueȱ ofȱ 48.61ȱ mgȱ kg -1 .ȱ Soilsȱ usedȱ inȱ
clayȱcontentsȱinȱtheȱsoilsȱ(Isitekhaleȱ et al. ȱ2013).
thisȱstudyȱshownȱwhereȱhigherȱheatȱsolubleȱSȱthanȱ
Sulphate sulphur
waterȱsolubleȱS,ȱsulphateȱSȱandȱadsorbedȱS,ȱtherebyȱ
indicatingȱtheȱreleaseȱofȱSȱbyȱwetȱandȱdryȱheatingȱofȱ
SulphateȱSȱstatusȱisȱfoundȱtoȱvaryȱconsiderablyȱfromȱ theȱsoilȱduringȱtheȱextraction.ȱHigherȱamountȱofȱheatȱ
15.35ȱ toȱ 43.36ȱ withȱ anȱ overallȱ meanȱ valueȱ ofȱ 24.14ȱ solubleȱSȱmightȱbeȱattributedȱtoȱreleaseȱofȱadditionalȱ
mgȱkg -1 ȱsoilȱ(Tableȱ4)ȱforȱ110ȱsamplesȱtestedȱinȱthisȱ amountȱofȱSȱfromȱorganicȱcarbonȱ(Ogehȱ et al. 2012)ȱasȱ
study.ȱTheȱpercentageȱcontributionȱofȱsulphateȱSȱtoȱ wellȱasȱclayȱparticlesȱonȱwetȱandȱdryȱheatingȱofȱsoilȱ
totalȱSȱalsoȱvariedȱfromȱ7.85ȱtoȱ9.94ȱperȱcentȱwithȱaȱ duringȱextractionȱ(BasumataryȱandȱDas,ȱ2012)ȱandȱ.ȱ
meanȱvalueȱofȱ7.8ȱperȱcentȱ(Figureȱ1).ȱSamplesȱfromȱ HeatingȱofȱsoilȱmayȱliberateȱgreaterȱamountȱofȱSO -
4
Kharibariȱbenchmarkȱsiteȱobservedȱtoȱhaveȱrelativelyȱ 2 -ȱSȱcovalentlyȱbondedȱtoȱorganicȱmatterȱ(Aderichinȱ
higherȱ sulphateȱ Sȱ withȱ aȱ meanȱ sulphateȱ Sȱ contentȱ 1960).ȱThisȱformȱofȱSȱconstitutedȱ5.97ȱtoȱ17.59ȱperȱcentȱ
ofȱ30.65ȱmgȱkg -1 ȱsoilȱfollowedȱbyȱthatȱofȱBinnaguriȱ withȱaȱmeanȱvalueȱofȱ15.70ȱperȱcentȱofȱ(Figureȱ1)ȱtotalȱ
seriesȱ(28.90ȱmgȱkg -1 ȱsoil)ȱunderȱJalpaiguriȱdistrict.
S.ȱTheȱstatusȱofȱheatȱsolubleȱSȱinȱsoilsȱwhenȱcomparedȱ
amongstȱ theȱ soilȱ seriesȱ andȱ benchmarkȱ sitesȱ fromȱ
whereȱtheȱsamplesȱwereȱcollected,ȱrelativelyȱhigher
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