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Composting is one of the most effective ways for recycling of organic solid waste. Various characteristics of different kinds of organic solid waste cause various physicochemical changes during composting, as well as the different composting conditions. Stability and maturity evaluation are the measurement for compost quality and the safe guarantee for its agricultural utilization. Stability evaluation of compost focuses on the impacts to environment after its agricultural utilization, while maturity evaluation pays attention on the phytotoxicity to plant. Stability and maturity of compost are affected by several factors, such as the characteristics of raw materials, the composting condition, and so on. Stability could be assessed by compost temperature, color, evolution rate of CO2, consumption rate of O2, content of NO3(-)-N and quantities of pathogen, etc. Temperature was suggested to be one of the most convenient parameters for stability evaluation. Maturity could be assessed by various parameters, including the chemical, biological, and phytotoxical parameters. Seed germination index, as the phytotoxical parameter, was recommended to be one of the most convenient and reliable parameters of maturity evaluation.

The contents of T-N, the ratios of soluble NO3-N/soluble T-N and soluble organic-N/soluble T-N increased after co-composting for 63 days of pig manure and sawdust with or without additional leaves, while the ratios of soluble NH4-N/soluble T-N decreased. In this study, addition of leaves was beneficial for maturation of pig manure composting, and it could shorten the composting time from 42 d to 35 d. The ratios of soluble NH4-N/soluble T-N, soluble NO3-N/soluble T-N and soluble organic N/soluble T-N correlated with seed germination index (GI) significantly, and it could be used for maturity evaluation.