Solubilization of Low-grade Rock Phosphate by Spent Wash and its Effect on Germination, Yield and P Uptake by Sorghumas a Fodder Crop

摘要

High-grade rock phosphate (P205 >30%) is essential for manufacturing P fertilizers. In India, out of the total rock phosphate (RP) reserve of 296.3 million tones (Mt), only 39% is of high grade which could meet hardly 35-40% of the demand of P fertilizers (Indian Bureau of Mines 2^10). The remaining demand is met through import which causes an increase in the price of P fertilizers. It is well known that the RP could be applied as a source of P in acid soils but about two-third area of the country comes under soils which are either neutral or alkaline in reaction (Sreenivas and Narayanasamy 2002). Therefore, there is a need to generate technologies for solubilizing P from indigenous low-grade RP to be applied directly in these soils. In this direction, various efforts have made viz., acidulation (Bolland 1994; Biswas and Narayanasamy 1998) and composting of RP with agricultural wastes (van de Berghe 1996) viz., rice straw, coir dust, wheat straw, green manuring, farmyard manure and urine. The concept of P solubilizing biofertilizers is also gaining importance (Biswas and Narayanasamy 2002). While exploring other feasible options, it was thought that the spent wash (SW) i.e. distillery effluent which is highly acidic (pH 3.5-4.5) and generated in huge quantities (6.8xl010 L yr1) in the country having considerable manurial potential (Chhonkar et al. 2000; Kumari and Phogat 2010), as well as problem of disposal. It will be worthwhile to study the effect of SW on P solubilization from indigenous low-grade RP. As SW is very harmful to aquatic fauna and flora if discharged directly into water bodies, land disposal is the only option. The present investigation was, therefore, carried out to study the solubilization of indigenous low-grade RP by SW andevaluate the effect of SW-treated RP on germination, yield and uptake of P by sorghum as a fodder crop.