Effect of pH on the adsorption of phosphate and potassium in batch and in column experiments

Abstract

The effect of increasing pH, through incubation with Ca(OH)2 and NaOH, on the adsorption of phosphate (P) and potassium (K) was examined in batch and in column experiments. In column experiments, an increase in pH from 5.2 to 8.2 decreased the adsorption of P and increased that of K which resulted in an increased leaching of P and a decreased leaching of K. In a batch experiment, however, an increase in pH resulting from incubation with NaOH gave similar results to those of the column experiment, whereas an increase in pH due to Ca(OH)2 addition caused the opposite effect on the adsorption of both P and K. The difference between the batch and the column experiments in the effect of incubating soil with Ca(OH)2 on the adsorption of P and K is related to the concentration of Ca in the soil solution.