Impact of low molecular weight organic acids on soil phosphorus release in Inceptisol and Alfisol

Secretion of LMWOAs by plants is one of the important mechanisms to make fixed soil phosphorus (P) bioavailable to plant. But the effectiveness of different LMWOAs in enhancing the soil available P varies significantly with the pH of the soil. Therefore the present study was undertaken at ICAR-IARI, New Delhi during 2018-19 to assess the effect of oxalic and citric acid in increasing the soil available phosphorus in two soil orders i.e. Inceptisol and Alfisol, during different intervals of incubation (i.e. 0, 15, 30, 45, 60 and 90 days). The results showed that there was an increasing trend in soil available P release pattern under both the LMWOAs treatments up to 60 and 45 days of incubation in Inceptisol and Alfisol, respectively and after reaching this threshold value, it attained declining trend. Citric acid was found to be most effective than oxalic acid in mobilizing soil phosphorus in the acidic soil (Alfisol), whereas oxalic acid was superior in neutral soil (Inceptisol). With increasing rates of both LMWOAs, the soil available P increased significantly. Thus, the application of LMWOAs will reduce the excess application of phosphorus and its build-up in soils and causing eutrophication of water bodies.