Methane (CH
4) and nitrous oxide (N
2O) are greenhouse gases; further, paddy fields are one of the anthropogenic sources of CH
4. In particular, “Fuyumizu-tambo,” an early flooded organic paddy field, is known to be the primary source of CH
4. Thus, we observed CH
4 and N
2O emissions using the chamber method in the “Fuyumizu-tambo” customary paddy fields from 2013 to 2014 at Bibai City, Hokkaido, Japan. Thus, a relation could be observed between the soil’s degree of dryness during mid-summer drainage, which is a CH
4 release-inhibiting period; furthermore, CH
4 was observed to be slightly released until the soil became completely dry. Because of the water retentivity of the “torotoro layer,” a type of soil containing abundant organic matter content owing to the stirring action of worm fish, drying is difficult, which results in the formation of an oxidation-reduction border domain. Therefore, the release of CH
4 is easy owing to the “torotoro layer.” In addition, although the abundant nitrogen content of the “torotoro layer” inhibited CH
4 emission, N
2O emission is not correlated to the total nitrogen (TN) concentration of the “torotoro layer,” and hence, nitrogen content directly does not cause N
2O production. Therefore, controlling the water retentivity and TN concentration of the “torotoro layer” could suppress CH
4 and N
2O emissions from the paddy fields.
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