Influence of Organic Acids on Phosphate Sorption and Availability in an Alfisol of Nigerian Guinea Savanna

Abstract

The combined application of organic acids and inorganic phosphate fertilizer has been suggested as a means of reducing phosphate adsorption and increasing the availability and solubility of applied phosphate in weathered tropical soils. We studied the effect of some selected organic acids on phosphate sorption and availability in an alfisol of Nigerian Guinea Savanna soil under laboratory conditions. Five levels of phosphorus (0, 50, 100, 200 and 400 μg g-1) with or without the addition of 0.05 M concentration of acetic, citric and tartaric acids were introduced into the soil in a completely random design at three replicate. The concentration of phosphate sorbed by the soil in the treatment without the introduction of organic acid (control) was significantly( P≤ 0.05) greater than the concentration of phosphate sorbed when organic acid was added irrespective of the organic acids used. The capacity for reduction on P adsorption and increased in P availability appears to followed the order of citrate > tartrate > acetate (31, 43 and 70mg kg-1 respectively). These three organic acids have the potentials to increase the availability of P in soil but need to be evaluated at the field scale.