Phosphate Desorption from Soils and Sediments with Varying Levels of Extractable Phosphate

Abstract

AbstractDesorption of P from soils and sediments was studied using sequential (10‐cycle) batch equilibration in 0.01M CaCl2 for equilibration periods of 2, 60, 480, 1,440, and 5,760 minutes. Soils with high Bray P1‐extractable P contained a pool of easily desorbable P which was depleted by the fifth cycle. Stream suspended sediments, bottom sediments, and soils low in Bray‐extractable P released small, but constant, amounts of P. Desorption of P from high extractable P soils was independent of equilibration time for the first two equilibrations, but obeyed first‐order kinetics for the subsequent eight extractions. Phosphate desorbed from all soils and sediments was highly correlated with Bray P1‐extractable P. The sediments and Hoytville soils from Defiance County, Ohio, gave a linear relationship between Bray P1 and desorbable P, while the Hoytville soils from the tillage study gave a quadratic increase in desorbed P with increasing Bray P1‐extractable P.