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Abstract Emission rates of CH4 from four Japanese paddy fields were measured throughout the cultivation period in 1988 by using the closed chamber method. Large seasonal variations of the CH4 flux were observed. The emission was closely related to the decrease of the redox potential (Eh) in paddy soils. Drainage and supplementary application of mineral fertilizer substantially reduced the CH4 emission. Emission rates of CH4 differed markedly with the soil types. The highest rate was observed in a paddy field consisting of Peat soil (44.8 g-CH4/m2 during a cultivation period), followed by Gley soil (8.0-27.0). The emission rates in the Andosols were significantly lower (0.6-12.6). Application of rice straw at a rate of 6-9 t/ha to the paddy fields increased the CH4 emission rates 1.8- to 3.5-fold. Application of compost slightly increased the CH4 emission. Annual emission rates of CH4 from individual plots were positively correlated with the contents of readily mineralizable carbon (RMC) in paddy soils collected before flooding, suggesting that RMC is one of the main factors affecting CH4 emission from flooded soils.
Yagi et al. (Sat,) studied this question.