[Effects of Gypsum on CH₄ Emission and Functional Microbial Communities in Paddy Soil]

In this study, the effects of gypsum (FGD) on CH₄ emission and functional microbial community in paddy soil were identified under five treatments, including FGDG₀(0 t·hm^-2), FGDG₁(2 t·hm^-2), FGDG₂(4 t·hm^-2), FGDG₃(8 t·hm^-2), and FGDG₄(16 t·hm^-2). The methane flux was determined using static chamber and chromatography. Bacterial community structure and its effect on soil bacterial community structure, and the abundance of methanogenic and methanotrophs were measured via high-throughput sequencing and quantitative PCR. The results showed that after treatment with desulfurated gypsum, pH of the soil increased significantly (P<0.05). Redox potential, organic carbon, and available potassium content increased, with no significant difference (P>0.05). The average emission flux of CH₄ reduced with the increase of desulfurated gypsum content, following the following trend:FGDG₁ > FGDG₂ > FGDG₃ > FGDG₄. They decreased by 31.56%, 57.30%, 83.60%, and 90.66%, respectively, compared with the control. Compared with the control, FGDG₁ and FGDG₂ increased the richness and variety of soil bacteria. However, when the application amount exceeds 4 t·hm^-2, the richness and variety of soil bacteria decrease. Compared with the control, the relative abundance of sulfate-reducing bacteria in paddy soil increased significantly by 6.98%-13.56%. The abundance of the methane-oxidizing bacteria pmoA gene increased by 0.3%-6.2%. The abundance of the methanogen gene, mrcA decreased significantly by 2.4%-15.8%, while the abundance ratio (pmoA/mcrA)increased with the increase of the amount of desulfurated gypsum. Correlation analysis showed that the average emission of CH₄ was markedly negatively correlated with the relative abundance of the sulfate-reducing bacteria and pmoA/mcrA percentage in soil, and significantly positively correlated with methanogenic gene, mcrA. In summary, desulfurated gypsum can improve the diversity of bacterial communities and reduce the emission of CH₄ in the paddy soils.