The effect of modified biochar on methane emission and succession of methanogenic archaeal community in paddy soil

Modified biochars have been widely applied in ameliorating environmental problems. However, the effect of modified biochar on suppressing CH4 emission in rice paddy soil is not fully understood. In order to further study CH4 regulation in paddy soil via the modification of biochar and explore its influence on key archaeal communities, two modified biochars were generated with the pre-treatment of nitric acid (NBC) and hydrogen peroxide (OBC), respectively, and a control group was setup with water-washed biochar (WBC). Results showed that NBC significantly suppressed CH4 emission, followed by OBC and WBC, while NBC promoted the CO2 emission. Besides, the addition of biochars inhibited the accumulation of acetate and H-2 in rice paddy soil, especially in the NBC treatment. 16S rRNA gene sequencing revealed that biochars amendment increased alpha-diversity of archaeal community and the modified biochars could mitigate the loss of alpha-diversity in the early stage of anaerobic incubation. Additionally, NBC amendment largely declined the relative abundance of methanogens (especially Methanosarcina) in archaeal community, while OBC and NBC promoted the relative abundance of Candidatus_Methanoperedens. Via Spearman's correlation coefficient analysis, NBC had positive correlations with Methanosaeta, and OBC showed a negative correlation with Methanocella. Overall, this study provided a practical way to regulate the CH4 emission and associated methanogenic archaea via the amendment of different modified biochars in rice paddy soil.

Automated summary

This study investigated the method of using different modified biochars to improve CH4 emissions and associated archaea in rice paddy soil. The results showed that nitric acid-treated biochar significantly suppressed CH4 emissions and increased CO2 emissions in soil. Additionally, the addition of biochars inhibited the accumulation of acetate and H-2 in rice paddy soil. 16S rRNA gene sequencing revealed that biochars amendment increased alpha-diversity of archaeal community and the modified biochars could mitigate the loss of alpha-diversity in the early stage of anaerobic incubation.