Influence of organic acids on mobilization of inorganic and organic phosphorus in soil

The role of four organic acids (lactic, formic, citric, malic) on the mobilization of phosphorus in available form for the plant nutrition was assessed with three different soil types. The results indicated that malic acid was poor at mobilizing phosphorus from all the tested soils, while lactic, formic and citric acid were capable of mobilizing significant quantities of PA strong correlation (R² = 0.68 to 0.88) between release of P from inorganic (Pi) and organic (Po) sources irrespective of different organic acids was observed. The mobilization was 1.8 to 3.9 times higher from unavailable Pi sources than Po sources and depended on the type of organic acid present in the system. Per unit organic acid efficiency was maximum in Inceptisol followed by Aridisol and Alfisol. The efficiency to release P also depends on the pH of the soil (r = −0.80, n = 84, p < 0.001). The minimum soil solution concentration needed to start P mobilization due to different orgaic acids irrespective of the soil varies from 0.2 to 0.4 mM. The efficiency of different organic acids to mobilize P follows the order: lactic acid > formic acid > citric acid > malic acid.