Substance Changes and Maturity Evaluation During Pig Manure Composting

The physical-chemical changes and maturity evaluation during pig manure composting at initial C/N ratio of 29 and 16 respectively were studied in this research. The results showed that the content of soluble organic C/N ratio, solid C/N ratio, dissolved organic carbon (DOC), and soluble NH + 4-N decreased after composting, which reflected the maturation process during pig manure composting. The seed germination index (GI) showed that pig manure compost at initial C/N ratio of 29 reached mature after composting for 49 days, while the compost at initial C/N ratio of 16 needed longer time than 63 days for further composting. In this study, the over-high content of salt in the compost at initial C/N ratio of 16 might contribute to the stronger phytotoxicity. Maturity of compost was influenced by lots of factors, so using a single chemical index for its evaluation was unilateral and unscientific. The seed germination index is the recommended index for maturity evaluation of solid organic waste compost.