Phosphate sorption by Greek alkaline soils evaluated with a modified Freundlich Equation

Phosphate adsorption of calcareous and non calcareous alkaline Greek soils was studied using the Freundlich Equation modified as to take also into account q , the quantity of phosphorus (P) already existing in these soils. Relatively high amounts of phosphate added were adsorbed, with a minimum of 44.5% at the highest level of P addition, being 600 μg P/g soil. The fit of the modified Freundlich Equation to the experimental data was best, when the values of bicarbonate extractable P were assigned to q , in comparison to both lower and higher values, Correction for q as above, resulted also in a statistically significant positive relationship between the Freundlich coefficient a , a capacity term with respect to P adsorption, and OM of the soils studied.