Methane emissions from double-rice cropping system under conventional and no tillage in southeast China

A field experiment was carried out to investigate the methane emission pattern in a double-rice cropping system under conventional and no tillage in southeast China. The treatments included conventional tillage cultivation in both early rice and late rice (T–T) and conventional tillage in early rice but no-till in late rice (T–NT). The maximum methane emission rate of T–T and T–NT was 21.71 mg m−2 h−1 and 24.70 mg m−2 h−1 in early rice, respectively; and 18.52 mg m−2 h−1 and 7.32 mg m−2 h−1 in late rice, respectively. The seasonal amount of methane emission from the T–T and T–NT was not significantly different in early rice, but significant different (P < 0.05) in late rice, with the values 6.57 g m−2 and 3.04 g m−2, respectively. In comparison with early rice, the seasonal amount methane flux of late rice was reduced by 29% and 68% in the T–T and T–NT, respectively. The decrease of methane emission in the T–NT was attributed to lower dissolved organic carbon (DOC) content and higher soil bulk density. In conclusion, no tillage practice conducted in rice cropping season will markedly decrease methane emission for the rice cropping system.

► No-till reduced methane emission significantly in paddy field. And it did negligibly affect on the methane flux after tillage in the early rice.
► The soil DOC content of no-till was significantly lower than that of the conventional tillage; however, the surface soil (0–10 cm) bulk density was significantly higher than that of the conventional tillage.
► The methane flux of late rice was lower than early rice in both the treatments in this double-rice cropping system.
► The lower DOC content may be another important factor resulting in lower methane emission besides the higher soil bulk density in no-till paddy field.