Competitive Adsorption of Phosphate with Malate and Oxalate by Tropical Soils

Abstract A study about the competition between organic anions (oxalate and malate)—currently present in the rhizosphere and phosphate for adsorption sites in tropical soils—indicate that in the presence of organic anions, phosphate adsorption by soils is reduced. The extent of such reduction is dependent on the way in which either phosphate or the organic anion are added to the soil. The organic oxyanions studied are more rapidly adsorbed to the soil surface than the phosphate; consequently those anions, when existing in the rhizosphere, can improve the phosphate status of soil.