Solubilization of phosphorus from low-grade Udaipur Rock phosphate using spent wash

For manufacture of P fertilizer a high grade quality rock phosphate (>30% P₂O₅) is required. In India, there is a predominance of low grade rock phosphate reserves and out of 260 million ton only 15.3 million ton is of high grade quality. Rock phosphate is usually inert in alkaline and calcareous soils. While exploring the options available for increasing the solubility of low grade RP, it was thought that the spent wash which is highly acidic (pH: 3.5–4.5) and generated as a waste in huge quantities (6.8xl0¹⁰ litres/year) in the country, may be utilized for this purpose. Spent wash has considerable manurial potential. The extent of P-solubilization from low-grade Udaipur rock phosphate (RP) by spent wash (SW) was studied by mixing RP and SP in different ratios i.e. 1:1, 1:2, 1:5, 1:10, 1:20, 1:40, 1:60, 1: 80 and 1:100. The amount of P solubilized, increased with increasing rate up to RP:SW::1:20 and thereafter, decreased.