POTASSIUM-CALCIUM EXCHANGE EQUILIBRIA IN SOME SOILS OF HARYANA

Potassium-calcium exchange equilibria was studied on four soil samples from semi-arid regions of Haryana, India, differing in textural compo sition and cation exchange capacity, It was observed that major portio n (about 80%) of normalized exchange isotherms of all the four soils l aid above the diagonal indicating the higher preference of K over Ca, The values of standard free energy change of the exchange reaction (De lta G(r)) was highest for soil-4 (CEC 16.0 Cmol (p+)/kg) and lowest fo r soil-2 (CEC 5.28 Cmol (p+)/kg). The values of different exchange sel ectivity coefficients (K-G, K-V, and K-KDO) decreased steeply with inc rease in exchangeable potassium percentage (EPP). The values of differ ent exchange selectivity coefficients were not constant over the entir e range of isotherm, suggesting the presence of different sites for K specificity on the exchange complex of these soil samples.