Co-Composting Urban Waste, Plant Residues, and Rock Phosphate: Biochemical Characterization and Evaluation of Compost Maturity

Co-composting of urban wastes (UWs) and plant residues with rock phosphate (RP) produces quality compost and reduces the use of chemical phosphorus fertilizer. Biochemical process of three compost piles (P): P-1- 50% UW + 30% rice straw (RS) + 10% sawdust (SD) + 8% RP + 2% sugarcane trash (ST), P-2- 50% UW + 23% RS + 10% SD + 15% mustard oil cake + 2% ST, and P-3- 95% UW + 5% RP was studied. Decomposition rate followed first-order kinetics and maximum (77%) was in P-3. The highest bacterial population was found in P-2 having higher cumulative CO2 evolution (53.76 mg CO2 g(-1) volume solid). Prevalence of phosphate-solubilizing bacteria was 2.0 to 6.3 Log(10) Cfu g(-1) dry weight and concentrated in RP-amended piles. Humic acid of compost was classified as rotteprudukte. Final pH (7.5 to 8.0) and germination index (>90) proved that the compost was mature. P-3 compost (1 t ha(-1), fresh weight) had potential to supply 25 kg phosphorus.