Characterizing soil fertility by ion diffusive flux measurements

Abstract

The general acceptance of diffusion as a rate-limiting step in transferring ions to plant roots was considered in characterizing soil fertility. Soil ion diffusive flux measurements to an exchange resin were measured with two soil: resin cells, one with untreated soil, the other with the same soil fertilized with P, K, and Cl. The P, K, and Cl that diffused to the resin of each cell was extracted and determined. Using only these measurements and some simplifying assumptions of diffusion theory, calculations were made of the soil's P and K solution concentration, adsorbed concentration, a capacity factor, transmission factor, and quantity of fertilizer needed to attain any desired flux. Excellent to fair correlations existed between these calculated values and traditionally measured chemical quantities. Plant uptake of P and K was generally well correlated with diffusive flux measurements as well as traditional chemical measurements.