DESCRIPTION OF DESORPTION OF PHOSPHATE FROM SOIL

After incubation with soil, phosphate was desorbed in dilute calcium chloride solutions. After short periods of incubation, the amount of phosphate desorbed increased rapidly at first but then net re‐adsorption occurred. After long periods of incubation, desorption was slower and there was no net re‐adsorption with prolonged desorption. Desorption was described in terms of two limiting values: the amount of phosphate (K) which would be desorbed as the concentration of phosphate approached zero, and the solution concentration of phosphate (Co) at which no desorption occurred. Both values decreased as the period of incubation increased. The value of K increased during the desorption phase, but the value of Co decreased. The decrease in Co during desorption was most marked after short periods of incubation and was important in describing the trend for re‐adsorption of phosphate. Copyright © 1979, Wiley Blackwell. All rights reserved