Effect of green manure amendment and flooding on methane emission from paddy fields

The effect of green manure amendment, flooding treatment and crop season on methane emission from paddy fields in Taiwan was investigated from August 1994 to July 1996. Sesbania amendment stimulated methane emission and the effect was more significant at the early growth stage of rice. Methane emission was higher in continuous flooding treatment than that in intermittent irrigation. Both redox potential and methane emission showed significant differences between these two irrigation systems. Methane concentration increased sharply with the depth of soil in the intermittent irrigation system due to oxidation; whereas it increased moderately in the continuous flooding treatment. The seasonal methane flux in the first crop season with chemical fertilizer was between 2.73 and 5.23 g m⁻²; while the value was between 10.54 and 10.56 g m⁻² in the second crop season. In the case of Sesbania amendment in the second crop season, the seasonal methane flux in the first crop season was 6.35 g m⁻²; while the value was between 14.43 and 30.12 g m⁻² in the second crop season. Total methane emission in the second crop season was about two to five-fold higher than that in the first crop season.