Citric acid influence on soil phosphorus availability

Citric acid is a low-molecular-weight organic acid exuded by the plant roots. Organic anions derived from this acid compete for phosphorus (P) adsorption sites in clay minerals. The objective was to evaluate the P availability by application of P and citric acid tothe soil. For this purpose, an experiment in green house was conducted at the rates of 0, 45, 90, and 180 mg dm−3 P in Entisol and 0, 100, 200, and 400 mg dm−3 P in Oxisol, combined with 0, 0.5, 1.0, and 2.0 mg dm−3 citric acid in pot. In the Entisol, 115 mg dm−3 of P and 0.7 mg dm−3 of citric acid resulted in maximum corn growth. However, in the Oxisol, the estimated rates were 299 mg dm−3 of P and 1.3 mg dm−3 of acid citric. Citric acid use in Entisol and Oxisol increased P availability of corn plants.