Effect of Biochar Amendment on Methane Emissions from Paddy Field under Water-Saving Irrigation

Biochar has been proposed as a new countermeasure to mitigate climate change because of its potential in inhibiting greenhouse gas emissions from farmlands. A field experiment was conducted in Taihu Lake region in China to assess the effects of rice-straw biochar amendment on methane (CH4) emissions from paddy fields under water-saving irrigation using three treatments, namely, control with no amendment (C0), 20 t ha−1 (C20), and 40 t ha−1 rice-straw biochar amendments (C40). Results showed that biochar application significantly decreased CH4 emissions by 29.7% and 15.6% at C20 and C40 biochar addition level, respectively. C20 significantly increased soil dissolved organic carbon, total nitrogen, and NH4+-N by 79.5, 24.5, and 47.7%, respectively, and decreased NO3−-N by 30.4% compared with C0. On the other hand, no significant difference was observed in soil pH and soil organic carbon in all treatments. C20 and C40 significantly increased and decreased soil oxidation-reduction potential, respectively. Compared with C0, rice yield and irrigation water productivity significantly increased by 24.0% and 33.4% and 36.3% and 42.5% for C20 and C40, respectively. Thus, rice-straw biochar amendment and water-saving irrigation technology can inhibit CH4 emissions while increasing rice yield and irrigation water productivity. The effects of increasing rice yield and irrigation water productivity were more remarkable for C40, but C20 was more effective in mitigating CH4 emission.