Methane consumption under the influence of different nitrogen sources in a tropical soil ecosystem

In order to minimize methane (CH4) concentration in the atmosphere we need to better understand CH4 consumption in agricultural soils. Nitrogen application to agriculture is predicted to increase significantly in the coming years to meet food security needs. However, the interaction between soil nitrogen and CH4 consumption is poorly understood. Experiments were carried out to evaluate CH4 consumption under the influence of the three nitrogen sources comprising N2(at ambient+5% and ambient+10%),NO3-N (at 10 mM and 20 mM) and NH4-N (at 10 mM and 20 mM). CH4 consumption was evaluated at different CH4 concentrations and feeding cycles to validate the effect of nitrogen. Among different N sources, N2 stimulated CH4 consumption potential by about 1.11-1.71 times over that in the absence of additional nitrogen (control), while N in the form of both NO3 and NH4 inhibited CH4 consumption by 1.14-2.18 times than in the control. CH4 consumption rate increased with CH4 feeding cycles. The effect of N sources on CH4 consumption followed similar trends irrespective of the N rate added.N2 stimulated the abundance of both nifH and pmoA genes. Abundance of methanotrophs pmoA gene copies and nitrifiers amoA gene copies were more in NH4-Namended soil than NO3-N.Available NO3 content in soil increased 9-30% with CH4 driven N2 fixation. This study concludes that N2 stimulated CH4 consumption while nitrogen in the form of NO3 and NH4 inhibited CH4 consumption in a tropical vertisol.