Influence of Soil Organic Matter in Releasing Soil Nitrogen

Total extractable N and extractable non-humic N were determined in the soils by extraction with 0.01 M CaC₂, before and after removal of organic matter (O.M.) from the soils. After complete removal of O.M. from soils, organic matter fractions, viz., humic, fulvic and hymatomelanic acids along with N source were added in proper doses. Total extractable N showed an increase in presence of organic matter fraction. Effect of lime in releasing noil N in presence or absence of organic matter was also investigated. Lime was added to organic matter free soil with different O.M. fractions and N source at pH 7.0–8.0 and 5.0–5.5, and an effective increase in extractable N was noticed. It was noticed that humic andfulvic acid fractions of soil humus were more effective in inereasing the availability of N in soils. Exchange studies were made with resin to determine N release. It was found, in most of the cases studied, that the amounts of extractable and exchangeable N were nearly the same.