Effect of potassium saturation on different exchange selectivity coefficients in soils

Exchange equilibria of K⁺-Ca²⁺ was established on soils with different texture and organic matter content. The data on the composition of the equilibrium solution and the exchange complex were used to calculate some selectivity coefficients viz. Gapon (K_G), Vanselow (K_V), Krishnamoorthy Davis Overstreet (K_KDO), K_C and K_N. None of these selectivity coefficients was constant at different levels of K-saturation. The values of selectivity coefficients were higher for higher organic matter content soil than low organic matter content soil.