Effects of inoculants on enzymes activities of pig manure during high temperature composting

An experiment was carried out with mixed materials of pig manure and wheat straw either with or without inoculants with microorganism agent (two treatments, one with agent, the other was CK) to study changes of various enzyme activities (including cellulase, sucrase, urease, dehydrogenase, catalase, polyphenol oxidase) during high- temperature composting process in a static state. The relationships of enzyme activity and E4/E6, enzyme activity and electrical conductivity(EC) were investigated. Results showed that the composting temperature was increased, and high temperature decay period was prolonged by adding microorganisms. All tested enzyme activities were bigger in the treatment with microorganism agent than those in CK treatment, and changes of enzyme activities were different with enzyme types and composting period. Cellulase and sucrase of composting had higher activities at the high temperature stage while decreased rapidly at the low temperature stage. Activities of urease and polyphenol oxidase reached peak values with temperature declining at later composting stage. And maximum activities of dehydrogenase appeared at the middle stage of composting period. However, catalase activities dropped down gradually during the whole composting period. There was a significant positive correlation between the enzymes including cellulase and dehydrogenase activities and EC values, while there was a positive correlation between the catalase activity and E4/E6 for both treatments. Enzyme activities during composting can be used to evaluate mineralization and humification processes.