The chemistry and mineralogy of phosphorus in excessively fertilized soils

Abstract

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 ³¹P 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 ³¹P NMR has allowed the identification of some of the organic P moieties, although their relative contribution to bioavailability is not well understood.

Key words:

• phosphorus
• soils
• nuclear magnetic resonance
• electron microscopy
• solubility equilibria