Changes of Various Nitrogen-containing Compounds in Composting of Chicken Manure and Indexes of Maturity Evaluation

Evaluation of composting maturity is important for successful use of composting product in agricultural production as a recycling strategy. Unfortunately, the evaluation system for assessing different composting product for their stability and quality has not well developed yet. The objective of this study is to establish a reliable composting stability test for chicken manure. Based on the dynamic changes of various nitrogen-containing compounds during chicken manure composting in a commercial composting facility, total nitrogen (TN) , hydrolyzable nitrogen (HN), total hydrolysable N (THN), ammonia N (AN),amino acid-N (AAN), amino sugar-N (ASN), HUN fraction, NH+4-N and NO-3-N at selected dates over composting 100 days were determined. The results indicated that TN, HN/TN and NH+4-N/TN kept stabile after composting 60 d, indicating that the final composting product was stable after 60 d, so they could be considered as the most adaptable evaluation parameters for composting maturity. In the meantime, the indexes of THN/TN, AN/TN, AAN/TN, ASN/TN, HUN/TN, NO-3-N/TN and NH+4-N/NO-3-N could be used as common evaluation parameters, since they increased or decreased gradually after 60d. Through further correlation analysis among various nitrogen-containing compounds and considering the practical application of composting, HN/TN and NH+4-N/TN were most adaptable parameters as evaluating maturity, while AAN/TN, NO-3-N/TN and NH+4-N/NO-3-N were common parameters as evaluating maturity. Chicken manure reached the basic requirement of maturity when HN/TN was 14.59%, NH+4-N/TN 9.87%, AAN/TN 14.58%, NO-3-N/TN 28.14%, NH+4-N/NO-3-N 0.325. The investigation mainly presented some maturity parameters about chemical parameters related to nitrogen, but the maturity of composting should be evaluated by various parameters including biological, chemical and physical parameters.