Distribution and Availability of Sulphur in some Terai Soils under Subtropical Zone of Eastern India
TheȱoverallȱlowȱwaterȱsolubleȱSȱstatusȱasȱcomparedȱ
increaseȱinȱsoilȱpHȱwouldȱresultȱintoȱdecreaseȱinȱtheȱ
toȱsulphateȱsulphurȱwasȱmostȱlikelyȱdueȱtoȱnaturalȱ
amountȱofȱSȱinȱthisȱform,ȱattributingȱitȱtoȱtheȱreducedȱ
leachingȱ ofȱ solubleȱ Sȱ compoundsȱ becauseȱ ofȱ lightȱ
adsorptionȱ ofȱ sulphateȱ inȱ soilsȱ andȱ itsȱ consequentȱ
soilȱtextureȱandȱprevalenceȱofȱhighȱannualȱrainfallȱ
lossesȱthroughȱleachingȱ(BasumataryȱandȱDas,ȱ2012).
(>2000ȱmm/annum)ȱareasȱ(Paulȱ et al. ȱ2011;ȱPaulȱandȱ
HeatȱsolubleȱSȱfollowedȱalmostȱaȱsimilarȱtrendȱtoȱthatȱ
Mukhopadhyayȱ2014).
ofȱadsorbedȱformȱofȱSȱinȱrespectȱofȱitsȱrelationshipȱ
Relationship among different forms of S and with
withȱsoilȱproperties.ȱItȱrecordedȱsignificantȱpositiveȱ
important soil properties
correlationsȱ withȱ organicȱ carbonȱ (rȱ =ȱ 0.33**)ȱ andȱ
totalȱ Nȱ (rȱ =ȱ 0.21*)ȱ contentȱ ofȱ soils.ȱ Significantȱ
Amongstȱ theȱ relationshipsȱ workedȱ outȱ betweenȱ
positiveȱcorrelationsȱwereȱalsoȱobservedȱwithȱCBD-
differentȱ formsȱ ofȱ Sȱ andȱ soilȱ propertiesȱ (Tableȱ 5),ȱ
Feȱ(rȱ=ȱ0.21*)ȱandȱCBD-(Al+Fe)ȱcombinedȱ(rȱ=ȱ0.20*).ȱ
totalȱ Sȱ contentȱ inȱ soilsȱ wasȱ foundȱ toȱ beȱ positivelyȱ
Whereasȱaȱnegativeȱcorrelationȱbetweenȱheatȱsolubleȱ
andȱsignificantlyȱcorrelatedȱwithȱtotalȱNȱ(rȱ=ȱ0.50**),ȱ
SȱandȱsoilȱpHȱwithȱitsȱr-valueȱveryȱcloseȱtoȱattainȱtheȱ
organicȱ carbonȱ (rȱ =ȱ 0.44**),ȱ finerȱ soilȱ separatesȱ
levelȱofȱsignificanceȱwasȱnoticed.
measuredȱinȱtermsȱofȱclayȱ(rȱ=ȱ0.36**)ȱandȱsilt+clayȱ
(0.33**)ȱ indicatingȱ therebyȱ theȱ presenceȱ ofȱ mostȱ ofȱ
Waterȱ solubleȱ Sȱ wasȱ foundȱ toȱ correlateȱ positivelyȱ
theȱSȱinȱtheseȱsoilsȱinȱassociationȱwithȱorganicȱmatterȱ
butȱnon-significantȱwithȱallȱtheȱsoilȱpropertiesȱtestedȱ
(Paulȱ andȱ Mukhopadhyayȱ 2009)ȱ inȱ teraiȱ soilsȱ ofȱ
inȱ thisȱ study,ȱ exceptȱ withȱ CBD-Feȱ (rȱ =ȱ 0.23*)ȱ andȱ
WestȱBengal.ȱTotalȱSȱcontentȱalsoȱrecordedȱpositiveȱ
oxalate-Feȱ(rȱ=ȱ0.19*)ȱwhichȱshowedȱsignificant.
correlationȱ withȱ CECȱ (rȱ =ȱ 0.21*),ȱ freeȱ ironȱ oxideȱ
Resultsȱ ofȱ correlationsȱ (r-values)ȱ amongȱ differentȱ
(CBD-Fe;ȱrȱ=ȱ0.20*)ȱandȱamorphousȱandȱorganicallyȱ
formsȱofȱSȱhaveȱpresentedȱinȱtheȱtableȱ6,ȱitȱwasȱobservedȱ
boundȱFeȱ(oxalate-Fe),ȱbutȱitȱwasȱnotȱsignificantȱinȱ
thatȱtotalȱSȱhadȱsignificantȱpositiveȱrelationshipȱwithȱ
caseȱofȱoxalate-extractable-Feȱcompounds.
allȱformsȱofȱSȱstudiedȱinȱthisȱexperiment.ȱKhalidȱ et
Correlationȱ studiesȱ (Tableȱ 5)ȱ revealedȱ thatȱ organicȱ
al .ȱ(2011)ȱobtainedȱsignificantȱpositiveȱrelationshipsȱ
formȱofȱSȱinȱtheseȱsoilsȱexhibitedȱsimilarȱrelationshipsȱ
betweenȱplantȱavailableȱSȱ(CaCl 2 ȱextractableȱSO4 -2 -S)ȱ
toȱthatȱofȱtotalȱSȱinȱrespectȱofȱtheȱpropertiesȱ viz. ȱtotalȱ
andȱtheȱtotalȱS,ȱorganicȱSȱandȱorganicȱCȱcontentsȱinȱ
Nȱ(rȱ=ȱ0.50**),ȱorganicȱcarbonȱ(rȱ=ȱ0.40**),ȱclayȱ(rȱ=ȱ
soilsȱofȱPakistan.ȱOrganicȱformȱofȱSȱexhibitedȱhighlyȱ
0.36**),ȱsilt+clayȱ(rȱ=ȱ0.32**)ȱandȱCECȱ(rȱ=ȱ0.21*);ȱbutȱ
significantȱandȱpositiveȱcorrelationsȱwithȱsulphateȱSȱ
withȱCBD-Fe,ȱitȱwasȱnotȱsignificant.
(rȱ=ȱ0.70**)ȱandȱwaterȱsolubleȱSȱ(rȱ=ȱ0.61**)ȱbutȱitȱwasȱ
alsoȱ relatedȱ positivelyȱ andȱ significantlyȱ withȱ heatȱ
SulphateȱSȱwasȱsignificantlyȱandȱpositivelyȱcorrelatedȱ
solubleȱ sulphurȱ (rȱ =ȱ 0.38**)ȱ andȱ adsorbedȱ formȱ ofȱ
withȱorganicȱcarbonȱ(rȱ=ȱ0.34**),ȱTotalȱNȱ(rȱ=ȱ0.27**)ȱ
sulphurȱ(rȱ=ȱ0.24*)ȱwithȱlowerȱmagnitudeȱofȱr-values.ȱ
clayȱ(rȱ=ȱ0.19*),ȱsilt+clayȱ(rȱ=ȱ0.24*),ȱoxalateȱFeȱ(rȱ=ȱ
StrongȱpositiveȱrelationshipȱofȱsulphateȱSȱwithȱwaterȱ
0.19)ȱ CBD-Feȱ (rȱ =ȱ 0.24*)ȱ (Tableȱ 5).ȱ Sulphateȱ Sȱ wasȱ
solubleȱ (rȱ =ȱ 0.80**),ȱ heatȱ solubleȱ (rȱ =ȱ 0.70**)ȱ andȱ
negativelyȱcorrelatedȱwithȱtheȱpHȱ(rȱ=ȱ-0.02)ȱofȱtheȱ
adsorbedȱformȱofȱSȱ(rȱ=ȱ0.46**)ȱindicatedȱthatȱtheseȱ
soil.
formsȱofȱSȱremainedȱinȱaȱstateȱofȱdynamicȱequilibriumȱ
Adsorbedȱ formȱ ofȱ Sȱ wasȱ foundȱ toȱ correlateȱ
(BasumataryȱandȱDas,ȱ2012).ȱAdsorbedȱSȱwasȱfoundȱ
significantlyȱ andȱ positivelyȱ withȱ organicȱ carbonȱ
toȱ maintainȱ aȱ veryȱ highȱ significantȱ andȱ positiveȱ
(rȱ=ȱ0.40**),ȱtotalȱNȱ(rȱ=ȱ0.26**),ȱsilt+clayȱ(rȱ=ȱ0.20*)ȱ
relationȱ withȱ heatȱ solubleȱ Sȱ (rȱ =ȱ 0.82**)ȱ suggestingȱ
andȱoxalate-Alȱ(rȱ=ȱ0.21*)ȱcontentȱofȱsoils,ȱbutȱwithȱ
thatȱwithȱincreaseȱinȱamountȱofȱheatȱsolubleȱSȱthereȱ
CBD-Alȱ correlationȱ valueȱ wasȱ merelyȱ belowȱ theȱ
wasȱanȱincreaseȱofȱtheȱadsorbedȱfractionȱofȱSȱinȱtheseȱ
levelȱofȱsignificance.ȱWhileȱaȱsignificantȱbutȱnegativeȱ
soils.ȱWaterȱsolubleȱSȱshowedȱsignificantȱandȱpositiveȱ
correlationȱ betweenȱ adsorbedȱ Sȱ andȱ soilȱ pHȱ (rȱ =ȱ
correlationȱbetweenȱwaterȱsolubleȱandȱheatȱsolubleȱSȱ
-0.20*)ȱ wasȱ observedȱ whichȱ clearlyȱ indicatedȱ thatȱ
(rȱ=ȱ0.38**)ȱwasȱobserved.
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