Department of Soil Science, Assam Agricultural University, Jorhat, Assam, 785013.
* Present address: Citrus Research Station, Assam Agricultural University, Tinsukia, Assam, 786125.
On the basis of the highest and the lowest K fixing and the releasing abilities, six surface soils (0–0.15 m) representing two each from Entisols, Inceptisols and Alfisols of Assam were selected for the kinetics of non-exchangeable K release from these soils. Tlte release pattern was studied by successive extraction with H-saturated cation exchange resin (Amberlite IR-120, AR). Four mathematical models viz., Zero order, First Order, Power function and Elovich equation were fitted into data on cumulative K release, and the befitting kinetics were ascertained from the highest and the lowest values of coefficient of determination (r2) and the standard error of estimate (SE). Results indicate that the Power function equation could adequately describe cumulative K release as against rest of the models used. Further, cumulative K as well as rate constant of Power function were highly correlated with dry matter yield and K uptake of exhaustive cropping (Guinea grass, Panicum maximum) vis-a-vis NH4OAc extractable K.
Non-exchangeable K release, resin extractable K, kinetics, Power function, Elovich equation, exhaustive cropping
