Do nitrogen fertilizers stimulate or inhibit methane emissions from rice fields?

Kamaljit Banger; Hanqin Tian; Chaoqun Lu

doi:10.1111/j.1365-2486.2012.02762.x

Do nitrogen fertilizers stimulate or inhibit methane emissions from rice fields?

Glob Chang Biol. 2012 Oct;18(10):3259-3267. doi: 10.1111/j.1365-2486.2012.02762.x. Epub 2012 Jul 10.

Authors

Kamaljit Banger^{1

2}, Hanqin Tian^{1

2}, Chaoqun Lu^{1

2}

Affiliations

¹ Ecosystem Dynamics and Global Ecology (EDGE) Laboratory, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, 36849, USA.
² International Center for Climate and Global Change Research, Auburn University, Auburn, AL, 36849, USA.

PMID: 28741830
DOI: 10.1111/j.1365-2486.2012.02762.x

Abstract

In rice cultivation, there are controversial reports on net impacts of nitrogen (N) fertilizers on methane (CH ₄ ) emissions. Nitrogen fertilizers increase crop growth as well as alter CH ₄ producing (Methanogens) and consuming (Methanotrophs) microbes, and thereby produce complex effects on CH ₄ emissions. Objectives of this study were to determine net impact of N fertilizers on CH ₄ emissions and to identify their underlying mechanisms in the rice soils. Database was obtained from 33 published papers that contained CH ₄ emissions observations from N fertilizer (28-406 kg N ha^-1 ) treatment and its control. Results have indicated that N fertilizers increased CH ₄ emissions in 98 of 155 data pairs in rice soils. Response of CH ₄ emissions per kg N fertilizer was significantly (P < 0.05) greater at < 140 kg N ha^-1 than > 140 kg N ha^-1 indicating that substrate switch from CH ₄ to ammonia by Methanotrophs may not be a dominant mechanism for increased CH ₄ emissions. On the contrary, decreased CH ₄ emission in intermittent drainage by N fertilizers has suggested the stimulation of Methanotrophs in rice soils. Effects of N fertilizer stimulated Methanotrophs in reducing CH ₄ emissions were modified by the continuous flood irrigation due to limitation of oxygen to Methanotrophs. Greater response of CH ₄ emissions per kg N fertilizer in urea than ammonia sulfate probably indicated the interference of sulfate in the CH ₄ production process. Overall, response of CH ₄ emissions to N fertilizers was correlated with N-induced crop yield (r = +0.39; P < 0.01), probably due to increased carbon substrates for Methanogens. Using CH ₄ emission observations, this meta-analysis has identified dominant microbial processes that control net effects of N fertilizers on CH ₄ emissions in rice soils. Finally, we have provided a conceptual model that included microbial processes and controlling factors to predict effects of N fertilizers on CH ₄ emissions in rice soils.

Keywords: fertilizer; methane; methanogens; methanotrophs; nitrogen; rice.