Investigating the relationship between temperature and soil CO₂ emission according to paddy water condition

The soil CO₂ emissions from rice paddy fields have a significant influence on net CO₂ fluxes throughout the year. Unlike other agroecosystems, rice paddy fields are flooded for most of the growing season. Over the course of this study, soil CO₂ emissions in rice paddy fields were observed under fallow, flooded, and drainage conditions using a closed-system portable chamber. It was found that the dried and bare soil in fallow paddy systems emit a significant amount of CO₂. On the other hand, the CO₂ released from the soil during flooding periods was suppressed by the water layer. In drainage conditions, the exponential curve of the relationship between soil CO₂ emissions and soil temperature was particularly evident. These results suggest that soil CO₂ emissions during fallow and drainage periods can exceed the level of CO₂ emissions that is suppressed under flooded conditions. However, immediately after draining or the occurrence of a rainfall event, the suppression of soil CO₂ emission by residual paddy water will provide valuable insights in the interpretation of agricultural carbon cycle models.