The Influence of pH on the Adsorption of Phosphate by Soils from the Guinea and Sudan Savannah Zones of Nigeria

Abstract An increase in pH of soils from the savannah zones of Nigeria to which varying quantities of phosphate were added increased the phosphate adsorbed by the soils. It is suggested that high pH increased the activity of hydroxy‐aluminum. Phosphate was adsorbed on the surface of the hydroxy‐aluminum species when the hydroxy‐aluminum‐phosphate attraction was strong enough to displace surface OH ‐ ions. As a result of increased P adsorption, the phosphate buffer capacity as well as the amount of phosphate required to attain a desired level of P in equilibrium solution increased. It is concluded that a successful liming program in the savannah soils must take into consideration increased phosphate fertilizer rates necessary for adequate nutrition.