KINETICS OF PHOSPHORUS RELEASE FROM SPODOSOLS - EFFECTS OF OXALATE AND FORMATE

The purpose of this study was to investigate the effect that these two organic anions have on the kinetics of inorganic- and organic-P release from the A, Bh, and Bt horizons of a representative forested Spodosol. Results showed that oxalate had little effect on P release in the A horizon, due to the lack of Al oxides to hold P. Conversely, oxalate greatly increased solution P in the Bh and Bt horizons. In the subsoil horizons, the release of P was rapid, followed the disappearance of oxalate from solution, and was coincident with an increase in pH. These facts suggested that P was released via a ligand-exchange reaction. A longer term reaction was consistent with the reprecipitation of the P as an amorphous Al phosphate. -from Authors