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Do nitrogen fertilizers stimulate or inhibit methane emissions from rice fields?
Author(s) -
Banger Kamaljit,
Tian Hanqin,
Lu Chaoqun
Publication year - 2012
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2012.02762.x
Subject(s) - fertilizer , nitrogen , agronomy , paddy field , irrigation , chemistry , methane , soil water , environmental science , sulfate , environmental chemistry , biology , soil science , organic chemistry
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.