Timing of midseason aeration to reduce CH4 and N2O emissions from double rice cultivation in China

Midseason aeration (MSA) is an effective way to reduce the combined global warming potential (GWP) of methane (CH4) and nitrous oxide (N2O) emissions [GWP (CH4+N2O)] during the rice (Oryza Sativa L.) growing season. Altering timing of MSA would affect CH4 and N2O emissions from rice cultivation. To evaluate the mitigation of net GWP (CH4+N2O) from double rice (Oryza Sativa Indica) cultivation by adjusting the time to start MSA, a two-year (2009 approximate to 2010) field experiment was conducted in Yingtan, Jiangxi Province, China. Four treatments, i.e. continuous flooding, early aeration, normal aeration (local practice) and late aeration, were adopted in the experiment. Results showed that compared with continuous flooding, midseason aeration significantly reduced seasonal CH4 emission and net 100-year GWP (CH4+N2O) from double rice cultivation without significant changes in grain yield. In the early rice season, the reductions in CH4 emission and net 100-year GWP (CH4+N2O) due to midseason aeration varied from 37% to 51% and from 36% to 50%, respectively, being lowest in early aeration and highest in normal aeration. In the late rice season, the reduction in CH4 emission and net 100-year GWP (CH4+N2O) due to midseason aeration varied between 49% and 57%, being lowest in late aeration and highest in early aeration. The GWP from N2O emission was negligible compared to that from CH4 emission. The findings indicated that the GWP in the late rice season could be effectively reduced by advancing suitably the time to start MSA.