Prediction of Parameters Describing Phosphorus-Desorption Kinetics in Soils of Galicia (Northwest Spain)

The risk of eutrophication due to loss of soil phosphorus (P) in runoff can be assessed by means of models simulating the release of soil P and its transport in runoff. One limitation of these models is that they seldom take into account the kinetics of P desorption from soil. In this work, to facilitate inclusion of kinetic aspects of P desorption in these models, equations to estimate parameters describing P-desorption kinetics from soil properties were developed. A modified Freundlich equation and several equations commonly used to describe P-desorption kinetics were fitted to kinetic data for P desorption from 31 surface horizons of soils of Galicia (Northwest Spain). Correlations were then determined between the parameters of these kinetic equations and soil physicochemical properties. Correlated properties were Al and Fe content and soil P fixation indices determined 1 d and 1 wk after P addition. By means of stepwise multiple regression analysis, equations were obtained that allow estimation of parameters describing P-desorption kinetics from soil properties, the dose of added P, and the soil-P contact time.