Effect of Nitrogen Levels on Methanogen and Methanotroph Populations in Rice Paddies

Rice production is a significant contributor to methane emissions, accounting for ap-proximately 11% of global anthropogenic emissions. However, methane emissions in rice fields could effectively be reduced by implementing proper management practices and careful cultivar selection. The impact of nitrogen fertilizers on methane emissions is mul-tifaceted, as these fertilizers enhance crop growth and influence the activity of me-thane-producing (methanogens) and methane-consuming microbes (methanotrophs), leading to complex outcomes in methane emissions. In this study, we used qPCR to quan-tify methanogens and methanotrophs using mcrA (methanogenesis-related gene) and pmoA (methane oxidation-related gene) primer sets under different nitrogen levels (0, 50, and 100%) and rice varieties. The results revealed that higher nitrogen input led to higher methanogen inhabitation in the rhizosphere. Additionally, the abundances of methano-gens and methanotrophs varied among the different rice varieties. Furthermore, it was observed that there may be an additive effect between the rice variety and nitrogen level used. These findings suggest that future breeding efforts should involve screening for me-thane-related microbes in rice cultivars adapted to low-nitrogen conditions. By identifying and selecting rice varieties that promote lower methanogen levels and higher metha-notroph inhabitation, significant steps can be taken to mitigate greenhouse gas emissions from rice cultivation.