Chemistry and Availability of Phosphate from Rock Phosphate Treated with Oxalic Acid in Calcareous Soil

Oxalic acid was used to solubilize low grade rock phosphate through wet blending in various ratios on dry weight basis and availability of P from blended rock phosphate was compared with superphosphate in calcareous soil up to 84 days. Available P increased in soil with increasing levels of oxalic acid with rock phosphate. At lower oxalic acid concentration, availability of P increased up to a certain level and thereafter decreased drastically due to formation of Ca-P in the system while at higher levels Ca-P decreased gradually. Oxalic acid: rock phosphate ratio of 1:2 wasfound comparable with SSP in respect to availability of P in soil.