The Energies of Replacement of Calcium by Potassium in Soils

Abstract

Abstract Energy of exchange is a measure of the intensity factor in the delivery of a balanced supply of nutrient cations from the exchange complex of the soil to the growing plant. Energies of exchange for the replacement of calcium by potassium in a soil may be computed from the cationic composition of water extracts from the soil. Cationic compositions of displaced soil solutions varied with the concentrations of soluble anions that in turn depended upon the moisture contents of the soils. But the variations were such that they reflected constant energies of exchange for each of the soils at different moisture contents. Energies of exchange for the replacement of calcium with potassium ranging from −3,500 to −4,000 calories were associated with potassium deficiencies in plants. Energies of exchange from −2,500 to −3,000 calories represented suitable balances between potassium and calcium. Energies of exchange of −2,000 calories or less were associated with excessive amounts of potassium in relation to the amounts of calcium that were present. The relationships between plant nutrition and energy of exchange appear to be universal in scope and applicable to all soils.