Changes in Nutrient Status During Preparation of Enriched Organomineral Fertilizers Using Rice Straw, Low-Grade Rock Phosphate, Waste Mica, and Phosphate Solubilizing Microorganism

An experiment was carried out to study the changes in nutrient contents during preparation of enriched organomineral fertilizers using rice straw, lowgrade rock phosphate (RP), waste mica, and phosphate- solubilizing microorganism (Aspergillus awamori). Composting reduced the total carbon (C) but increased total nitrogen (N) content with the progress of composting. This was reflected in the decrease of the C/N ratio. Significant increases in total phosphorus (P) and potassium (K) were also observed where both RP and waste mica was added along with Aspergillus awamori. Ammonium N (NH4(+)-N) decreased while nitrate N (NO3--N) increased at the end of composting. Olsen P content increased up to 90 days, thereafter decreased up to day 150, whereas ammonium acetate K (NH4OAc-K) increased gradually with the progress of composting. The study thus revealed that crop residue could be converted into a value-added product through composting technology using low- grade rock phosphate and waste mica along with phosphate-solubilizing microorganisms.