Abstract: 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 ecreased 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>0.8％.

Key words: grain nutritional quality, grain yield, summer maize, grain filling characteristics, nitrogen application rate