THE CHEMISTRY AND MINERALOGY OF PHOSPHORUS IN EXCESSIVELY FERTILIZED SOILS

Despite recent research and media attention on the environmental problems caused by nitrates, organics, and heavy metals, phosphorus (P) remains a significant pollutant of surface waters through its role in accelerated eutrophication processes. Excessively fertilized soils represent a major contributor to P loadings of surface waters. Several areas of research address the overall question of P bioavailability. The identification and characterization of P solid phases have been advanced by the application of electron optical techniques and P-31 nuclear magnetic resonance (NMR) spectroscopy. Several new methods have been proposed for describing P sorption and desorption and each works well on a limited number of soils or under limited conditions. Phosphorus desorption is particularly important with respect to P bioavailability, and a generally accepted method to predict desorption does not currently exist. Some of the accumulated P in excessively fertilized soils is in organic forms. The use of P-31 NMR has allowed the identification of some of the organic P moieties, although their relative contribution to bioavailability is not well understood.