Phosphate adsorption-desorption in selected vertisols

Abstract

Phosphate (P) adsorption -desorption characteristics of surface samples of 4 Vertisols were studied. The phosphate adsorption capacity of these soils was low, and ranged from 35 to 80 ug g-l of soil at 0.2 ug ml- l equilibrium solution P concentration. The Langmuir equation described the adsorption reasonably accurately at all solution P concentrations, and was much more accurate than the Freundlich, Gunnary, Tempkin and Dubinin-Radushkevich equations. P adsorption at 0.2 ug P ml- l equilibrium solution P concentration calculated from Langmuir isotherm was positively correlated with DTPA extractable Fe, but was not correlated with clay content. Neither P fertilization