The offsetting effect of soil carbon emissions on soil carbon sequestration in tobacco-rice rotation farmland limits the sustainable development of agricultural production. To investigate the potential of soil methane emission and the temporal variation pattern of soil organic carbon content in tobacco-rice rotation farmland. In this study, high-throughput sequencing technology was used. We analyzed the differences in soil organic carbon content and methane emission potential of tobacco-rice rotation farmland at different cropping years (10-20 years, 20-40 years and more than 40 years), as well as the changes in the structure and diversity of microbial communities involved in methane cycling as the cropping years were extended. The results showed that there were significant differences in soil methane emissions from tobacco-rice rotation farmlands with different cropping years, and soil methane emissions from tobacco-rice rotation farmlands with 20-40 years of cropping decreased significantly; the alpha diversity of soil methanogens communities decreased significantly during 20-40 years, while the differences in alpha diversity of soil methanotrophs communities with different cropping years were not significant; soil organic carbon drove the structure of methanogens communities , leading to a decrease in the alpha diversity of methanogens as well as the relative abundance of Methanocorpusculum in soils grown for 20-40 years, which was responsible for the decrease in soil methane emissions. Soil methane emissions were lowest in the 20-40 year tobacco-rice rotation, and increased again in the soils grown in the rotation for more than 40 years.
 

tobacco-rice rotation; planting years; methane emissions; soil organic carbon; methanogens; methanotrophs