Phosphorus Solubilization Through Organic Acids Production in Pressmud Composted with Rockphosphate

Rockphosphate enriched pressmud compost (RPEPMC) was prepared by mixing fresh pressmud with rockphosphate (RP) inoculated with a composite microbial culture consisting of Pseudomonas spp., Aspergillus spp., Streptomycetes spp., Penicillium spp. and Trichoderma spp. at 0.1 % (w/w) level. The production of organic acids and solubilization of phosphorus during pressmud composting was studied at 30, 60, 90 and 120 days of composting. The presence of oxaloacetic, citric, succinic, tartaric, malic and maleic acids in the compost was detected and quantified. In general the organic acids produced at 30 days were highest which rapidly decreased at 120 days of composting. The positive influence of various organic acids on solubilization of P from RP was evident from concomitant increase in citrate-soluble and water-soluble-P content in the compost. After 120 days of composting the end product had a stable C:N ratio and higher soluble P. Thus RPEPMC could be an alternative source of P fertilizer in crop production.