Organic acids and phosphorus solubilization in straw composted with rock phosphate

The effect of nitrogen, molasses and low-grade rock phosphate enrichment on the production of organic acids and solubilization of phosphorus during wheat straw composting was studied. The presence of glycolic, oxaloacetic, succinic, fumaric, malic, tartaric and citric acids was detected in a water extract of the compost. Their occurrence was very high, resulting in higher solubilization of added insoluble P at the beginning of 30 days, but thereafter decreased drastically reaching negligible amounts at 120 days of composting. Nitrogen addition increased the production of all the above organic acids. Nitrogen + molasses addition also increased all except oxaloacetic acid at 30 days and glycolic acid at both 30 and 60 days of composting. However the incorporation of both Mussoorie phos and Hyper phos precipitated out oxaloacetic, tartaric and citric acids and hence their concentration decreased in the aqueous solution. (C) 1998 Published by Elsevier Science Ltd.