Effects of ph and solvent/soil ratio on extraction of phosphorus from soils by various extracting solutions

Abstract

Eight extracting solutions were used to study the effects of pH and solvent/soil ratio on the amounts of phosphorus (P) extracted from 31 soils collected from Great Britain and Greece representing wide ranges in texture, parent materials, and soil characteristics. The amounts of P extracted by 0.5M HO Ac and NaOAc mixture buffered to five equidistant steps within the pH range from 4.00 to 5.25 were determined. The data from soils at seven different solvent/soil ratios obtained by plotting pH against P extracted showed that the solubility of P decreased significantly as the pH was raised above 4.00. On average, at solvent/soil ratios 3.125 and 200, the pH extracted decreased by 36% and 45%, respectively, for each unit rise in pH. The effects of solvent/soil ratio were studied over the range 3.125 to 200. The amounts of P extracted increased as the ratio increased. The magnitude of the ratio effect on the P extracted was, generally, in the order: HOAc > acetate buffer solutions > NaHCO₃, being substantially greater in the calcareous soils, except for the NaHCO₃ extraction.