Objective  The response mechanism of CH₄ emissions and related functional microorganisms in paddy fields to different types of straw were clarified, which will provide a theoretical basis for CH₄ emission prediction and mitigation in paddy soils.

  Method  A typical single-season paddy soil in Taihu Lake area was used as the research object, and the greenhouse cultivation experiment was set up to simultaneously monitor the CH₄ emission flux, rice yield, soil organic carbon, soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN) and other factors under different straw application treatments (rice straw, RS; wheat straw, WS; maize straw, MS) . The above factors were coupled with the microbial processes of CH₄ generation and oxidation, in which the community abundances of CH₄ emission-related microbes were quantitatively by molecular biology technology. Then the microbial response mechanism of CH₄ emissions to different types of straw application was elucidated.

  Results  The results showed that CH₄ emissions during rice growing period were significantly increased by 289.65%, 263.30% and 344.43% by RS, MS and WS treatments, respectively, and CH₄ emissions per unit yield increased by 210.40%, 182.35% and 282.80%, respectively. The seasonal dynamics of soil methanogenes (mcrA) abundance showed an upward trend along the rice growth, while the methanotrophs (pmoA) showed an upward and then downward trend. The RS treatment significantly increased the copy numbers of bacterial 16S rRNA and pmoA genes at the rice jointing stage, and the WS treatment significantly increased the copy number of mcrA gene during the mature stage, but the MS treatment had no significant effect on the above copy numbers.

  Conclusion  Correlation analysis and structural equation models showed that the abundances of bacterial, methanogens and methanotrophs, and microbial carbon-nitrogen ratio (MBC/MBN) were the main factors directly affecting CH₄ emission from paddy fields.