Distribution of Forms of Potassium and K Release Kinetics in Some Vertisol Profiles

Three soil series classified under Vertisols were studied for the distribution of different fractions of potassium and K release kinetics. Higher levels of water soluble and exchangeable K were found in surface horizons as compared with subsurface horizons. Uniformity in the levels of exchangeable K below the surface horizon was attributed to pedoturbation process. First order kinetics explained the K release data well as revealed from higher correlation coefficients and lower standard deviations. Similar K release rate constants (b) for all soils from the three pedons could be due to similarity in their mineralogical make up. Different fractions of K in soils showed highly significant correlations with K release constant (a).