Comparative Solubility Study of Four Phosphatic Fertilizers in Different Solvents and the Effect of Soil

Phosphate rocks (PRs) are suitable for direct application as a possible alternative to more expensive soluble phosphate fertilizers in agricultural fields. But the ability of the PRs to release phosphates in the plant available forms depends on the particle size and chemical and mineralogical characteristics of the PRs as well as the properties of the soil in which they are applied. So an experiment was conducted with four sources of phosphatic fertilizers namely Triple super phosphate (TSP – 21.75%P)), Partially acidulated phosphate rock (PAPR – 12.97%P)), Morocco rock phosphate (MORP – 14.87%P)) and Mussoorie rock phosphate (MRP – 8.12%P) whose solubility were tested in six different extractants namely 2% Citric acid, 0.002N Hydrochloric acid, N-Ammonium citrate, Bray-2P extractant, Olsens’s extractant and Morgan’s reagent under seven periods of incubation (1, 2, 3, 7, 10, 15 and 30 days), with and without soil. The results revealed that release of P were increased on addition of soil irrespective of fertilizers or extractants used. TSP released maximum P (3.05% - 3.27% with soil, 2.11% - 2.22% without soil) by the 7th day of incubation. The partially acidulated source was found to release P, higher than rock phosphates but lower than TSP, for the initial periods of incubation (1-3 days) (1.31%-1.34% with soil, 0.46% without soil) with an increase in the later periods (7th day onward) (1.27%-1.92% with soil, 0.55%-0.66% without soil). The PRs released maximum P after the 7th day of incubation. Among the different solvents, maximum release of phosphorus was observed by 2% citric acid followed by Bray 2P and Olsen’s extractants.