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

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.