Agricultural activities significantly contribute to emissions of key greenhouse gases (GHGs): carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).
Aerobic arable soils mainly emit CO2 and N2O, the latter being released in direct proportion of N fertilizer input.
By contrast, irrigated rice cropping systems under mostly anaerobic conditions are responsible for 5e20 per cent of CH4 emission from all anthropogenic sources and CH4 emissions contribute the majority of global warming potential (GWP) in rice systems .
The CH4 emission from irrigated rice fields is controlled by production, oxidation and transport processes.
Following flooding, strictly anaerobic methanogenesis (either acetoclastic or hydrogenotrophic) produces CH4 as terminal product of anaerobic mineralization of soil organic matter (SOM) degradation, in the absence of alternative electron acceptors (O2, NO 3 , Fe(III), and SO24 ) or microbes capable of using those.