Chemistry of Potassium Exchange Equilibria in Soils of Varying Mineralogical Composition

Q/I relations of soil potassium by thermodynamic approach and its modification, and Beckett's potential buffering capacity of soils having a wide variation in their mineralogical make up and physicochemical characters were measured. The potential buffering capacity (PBC) measurement and equilibrium studies indicated that these were being influenced not only by the nature and quantity of clay minerals present in the soil but also by certain physicochemical factors. PBC^K values were found to be relatively low in kaolinitic soils as compared with the illite dominated ones. The soils dominant in smectites showed intermediate values. Two new parameters namely, buffering capacity (BC^K_Se) and unified solution Q/I factor (USQI) were worked out on these soils by taking concentration ratio of K in soil solution as intensity factor and the K extracted by 1N NH₄ OAc as the quantity factor. These parameters appeared to have an advantage over those derived from Beckett's Q/I technique in some of the soils depending on the environmental condition.