Biochar amendment on greenhouse gases emissions and soil carbon sequestration in subtropical paddy fields: a ten-year study

Paddy field is one of the important sources for CH4 emissions, and can also be the carbon sink by soil carbon sequestration. In this study, a ten-year study was conducted to evaluate the long-term effects of biochar amendment on greenhouse gas emissions and soil carbon sequestration. Straw-derived biochar was applied once in 2012 at 24 and 48 t ha-1. The results showed that the annual CH4 emissions decreased by 20-50% as compared with no biochar amendment in the first four years after biochar addition. There were consistent CH4 emission reduction in the 10th year after biochar addition, with a reduction rate of 18-27%. The reduction of CH4 emission from paddy field was mainly related the improve of aeration, and the redution of the abundance ratio of methanogen/ methanotrophy. Biochar only increased N2O emissions in the first year after biochar addition due to additional nitrogen input caused by biochar addition. Biochar addition increased soil total organic content (TOC) in the first year after biochar addition, and the TOC contents showed no decrease after 10 years. Biochar addtion did not increase or decrease rice yield in a ten-year average. This indicated that biochar can be a useful measure for decreasing greenhouse gases emissions from subtropical paddy fields, and for increasing soil carbon sequestration in a long-term period.