Kinetics of Potassium Desorption from Important Benchmark Soils of India

Exchangeable potassium desorption from surface and sub-surface horizons of 22 benchmark soil series of India was studied employing four kinetic equations, i.e. first order, parabolic diffusion, Elovich and zero-order. The results demonstrated the usefulness of parabolic diffusion and first order equations for describing K desorption from these soils. Vertisols and Vertic Ustochrepts showed higher desorption rate constants (slope) of first order equation followed by kaolinitic Alfisols and Inceptisols and illitic Inceptisols, Alfisols, Entisols and Aiidisol whereas slope values of parabolic diffusion were higher for kaolinitic Alfisols and Inceptisols followed by illitic Inceptisols, Alfisols, Entisols and Aridisol and smectitic Vertisols and Vertic Ustochrepts. In general, sub-surface soils showed higher release constants than surface ones. Intercept values showed positive relationship with NH₄PAc extractable K status. While first order release rate constants showed positive relation with NH₄OAc-K status, it was negative with that of parabolic diffusion. The differences between these two models have been attributed to the differences in the theoretical assumptions in these equations.