[Dynamic changes of nitrogen forms in livestock manure during composting and relevant evaluation indices of compost...

In this paper, the dynamic changes of nitrogen (N) forms in different livestock manures were investigated during composting, and the relevant N evaluation indices of compost maturity were approached. The results indicated that during composting, the total nitrogen (TN) concentration in dairy cattle manure increased first and became steady then, but in other five test manures, it decreased first and became steady then. For all test manures, their hydrolizable nitrogen (HN) decreased after an initial increase, NH4(+)-N decreased first and became steady then, while NO3(-)-N had a persistent increase. Among the N indices of compost maturity, HN/TN and NH4(+)-N/TN could be selected as the adaptable parameters to evaluate the maturity, while NO3(-)-N/TN could be only used as a universal one. According to the required standard of compost maturity based on the comprehensive index GI (seed germination index), i.e., GI > 0.50, it was suggested that for the livestock manures except young pig manure, the basic requirements of their compost maturity were HN/TN < 20.77%, NH4(+)-N/TN < 10.06%, and NO3(-)-N/TN > 0.38%.