Cattle manure composting: Shifts in the methanogenic community structure, chemical composition, and consequences on methane production potential in a rice paddy

Compost application has been considered to be one of the most promising methods for sustaining soil quality and crop productivity and possibly attenuates the impact of methane (CH4) emission in rice paddies. The physico-chemical and biological characteristics of manure may vary, depending on the maturity of the compost. Therefore, compost obtained from different stages of maturation could differentially influence CH4 production in rice paddies following input into the fields. In composting samples, we investigated the effect of composting on alterations in physico-chemical characteristics and changes in methanogenic abundance and community structure in manure during the maturation process using a conventional static chamber method. Thereafter, CH4 production potential was monitored in soil samples amended with compost obtained from different composting stages (0 as a starting material, 7, 14, 21, 28, and 35 days after installation) via an incubation experiment. The results show that manure composting significantly decreased the methanogenic abundance and altered the methanogenic community structure by qPCR and T-RFLP analyses, respectively. The physico-chemical properties, such as labile carbon (C) and nitrogen (N) availabilities in manure, were gradually changed due to high temperature and oxygen supplement. These changes result in decreasing CH4 production in a rice field soil amended with composts. Our results suggest that composting is a promising approach to mitigate the impact of CH4 emissions in rice paddy fields with manure. In conclusion, composting should be indispensable for mitigating the impact of CH4 emission in manure-amended paddy soil during cultivation.