[Effects of Rice Straw Addition on Methanogenic Archaea and Bacteria in Two Paddy Soils]

Rice straw (RS) returning has an important effect on CH₄ emission in rice paddy soil. In the present study, two paddy soil types from Jiangxi (JX) and Guangdong (GD), respectively, with different amounts of added RS were incubated through microcosmic anaerobic incubation experiments to investigate the responses of methanogenic archaea and bacteria communities after relatively long-term incubation. The different amounts of added RS affected methanogenic archaea community structures in the JX soil to some extent but did not affect the GD soil. The mcrA gene copy number increased with an increase in RS amount in both soils. Under the same amount of RS, the copy number of this gene in the JX soil was greater than that in the GD soil. In addition, significant positive correlations were shown between the RS amount and the copy number of the mcrA gene, and the response of the copy number was more sensitive to the RS amount in the JX soil. Obvious differences in methanogenic archaea community structures were shown between two soils. Methanosarcinaceae, Methanocellaceae, Methanomicrobiaceae, Methanobacteriaceae, and unknown microorganism (494 bp) were detected in the JX soil, and Methanobacteriaceae, Methanosarcinaceae, and Methanocellaceae were observed in the GD soil. The bacterial communities exhibited obvious differences between the two soil types after 180 days of incubation. The bacterial diversity in the GD soil was higher than that in the JX soil, although the amounts of dominant bacteria in the JX soil, including Bacillus, Desulfovirgula, Thermosporothrix, Acidobacteria/Gp1, Acidobacteria/Gp3, and Ktedonobacter, were higher than those of the GD soil, including Longilinea, Acidobacteria/Gp6, Bellilinea, and Thermosporothrix. RS application promoted the growth of methanogenic archaea as important substrates. Moreover, different structures of methanogens and bacteria were shown between the two soil types after relatively long-term incubation.