Biochar improved soil health and mitigated greenhouse gas emission from controlled irrigation paddy field: Insights into microbial diversity

Biochar application (BA) and controlled irrigation (CI) can realize the resource utilization of biowaste and water respectively. Both BA and CI can affect soil carbon pool dynamics and greenhouse gas (GHG) emissions in paddy fields, but their synergistic effects and the microbial mechanism remain unclear. This study investigated the effects of BA on CO2 exchange, GHG emissions, and soil microbial diversity of paddy fields under CI. BA increased soil respiration rate (Rs) from CI paddy fields by 23.81%–41.45 %, possibly due to the increase of Curvibacter, while BA reduced global warming potential by 25.85%–37.84 %. The reduction of N2O emission under CI with BA may be attributed to the increase of Proteobacteria and the decrease of Nitrospira. CI decreased the net ecosystem exchange (NEE) and soil organic carbon but increased Rs and dissolved organic carbon, compared with flood irrigation. Lactobacillus and Mortierella were dominant bacteria and fungi at milk stage. In addition, BA and CI mitigated CH4 emissions and reduced the abundance of Russula. Both bacteria and fungi play important roles in soil carbon cycle, which is mainly affected by soil temperature, humidity, and ammonium. These results indicate that BA combined with CI is a promising cleaner production strategy to simultaneously improve soil health, mitigate GHG emission, and mediate soil microbial community structure.