Phosphorus isotherms sorption in semi arid soil.

The aims of this study were to determine the phosphorus (P) adsorption capacity of the semi-arid soils from Tunisian Sahel and to generate that relates these capacities to soil properties. Air-dried samples soils collected at four depths from three sites in the Sahel region of Tunisia (Chott-Mariem, Enfidha and Kondar). Soil chemical, physical and mineralogical properties were analyzed. 0,5g of each soil samples were shaken with increasing concentrations of solution P for 36 hr at 20 °C. The maximum of P adsorption were greatly influenced by soil organic matter, calcium, magnesium and clay content. Moreover, the data obtained was fitted using Langmuir and Freundlich isotherm functions. P adsorption data revealed that Langmuir equation (R2= 0.98) showed a better describe the adsorption phenomena over the Freundlich equation (R2 =0. 96) in all the three series.