Effect of Nitrogen Levels to Methanogen and Methanotroph Population on Rice Paddy

Abstract: Rice production is a significant contributor to methane emissions, accounting for approximately 11% of global anthropogenic emissions. However, there is potential for effectively reducing methane emissions from rice fields through the implementation of proper management practices and careful cultivar selection. The impact of nitrogen (N) fertilizers on methane (CH4) emissions is multifaceted, as these fertilizers not only en-hance crop growth but also influence the activity of methane-producing microbes (Meth-anogens) and methane-consuming microbes (Methanotrophs), leading to complex out-comes in CH4 emissions. In this study, we utilized qPCR to quantify methanogens and methanotrophs using mcrA (methanogenesis-related gene) and pmoA (methane oxida-tion-related gene) primer sets under different nitrogen levels (0, 50, 100%) and rice varie-ties. The results revealed that higher nitrogen inputs led to higher methanogen inhabita-tion in the rhizosphere. Additionally, the abundances of methanogens and metha-notrophs varied among different rice varieties. Furthermore, through the analysis of two-way ANOVA, it was observed that there may be an additive effect between rice variety and nitrogen level. Furthermore, enhancing agronomic traits related to yield can reduce methanogen inhabitation. These findings suggest that future breeding efforts should in-volve the screening of methane-related microbes in rice cultivars adapted to low nitrogen conditions. By identifying and selecting rice varieties that promote lower methanogen lev-els and higher methanotroph inhabitation, we can take significant steps towards mitigating greenhouse gas emissions from rice cultivation.