Comparison of different models for phosphate adsorption in salt inherent soil series of Dera Ismail Khan

Soil samples from three different soil series of Dera Ismail Khan namely Zindani, Tikken and Gishkori were collected and used for sorption study. The physico-chemical properties of these soil series were found to be alkaline and calcareous in nature, with low organic matter and high ECe and sodium adsorption ratio (SAR). Three adsorption equations viz. Langmuir, Freundlich and Tempkin were used to describe P adsorption processes. The results of the study showed that maximum adsorbed P of Gishkori, Tikken and Zindani series was 235.49, 152.78 and 128.45 mg kg^-1, respectively. By applying various models, P adsorption data revealed that Freundlich equation (R2 = 0.99) showed a better fit over the Langmuir equation (R2 =0. 97) in all the three series. The Tempkin equation did not show a good fit to the data (R2 = 0.89).