Effect of organic acids and silicate on phosphorus concentration, buffering capacity and release threshold level in soil

Various organic acids have been found to be associated with wheat and rice root zone. Among them malic, citric and tartaric acids are prevalent. To study the changes in P concentration, buffering capacity and P release threshold level, soils of different types were incubated with organic acids and silicates at different moisture levels for 20 and 50 days. Olsen's and CaCl₂ (0.01M) extractable P were measured. Tartaric, citric and malic acids alone and in combination with one another increased the solution P concentration. Silicate application along with these acids decreased P concentration in solution. From multiple regression analysis, it was found that the malic and tartaric acids have negative effect also. Malic, citric and tartaric acids influenced the Olsen's extractable P in the short term (20 days) period but not in longer period (50 days of incubation). Phophorus desorption isotherm describes the effect of acids and silicate on buffering capacity and release threshold level. It was found that citric acid in Inceptisol and tartaric acid in Alfisol was most effective in releasing non-labile phosphorus.