ISOTOPICALLY EXCHANGEABLE PHOSPHORUS IN SOILS

Abstract

Summary Methods used to determine isotopically exchangeabIe phosphorus in soils are described and briefly analysed. The influence of soil: solution ratio, orthophosphate ions added with radio‐phosphorus, the equilibrium pH, and the removal of increasing amounts of phosphate from the soil are investigated. A scheme is suggested for the subdivision of the total soil phosphate into four fractions on the basis of their abilities to exchange PO 4 ions with the phosphate in the soil solution. The relation between the labile pool of soil phosphate and this scheme is discussed.