Abstract
Improving cultivation management to reduce environmental loads, such as emission of greenhouse gases, are pressing tasks for the sustainable development of paddy field farming in the Asia monsoon region. From this viewpoint, it is important to predict nitrogen and carbon dynamics associated with changes in soil redox status under various water management regimes. Recent studies have demonstrated the effects of dissolved oxygen in infiltration water on the redox potential and nitrogen and carbon dynamics of soils. Therefore, in this study, we investigated the effect of air penetration from the soil surface on the soil redox potential profile by performing a column evaporation experiment using a paddy soil. During evaporation, the soil redox potential increased from the surface downward due to the penetration of small amounts of air. The onset of redox potential increments was slower than the air penetration front, in deeper layers or at higher evaporation rates, and the contribution of penetrated air to the soil oxidation state is considerably greater than that of dissolved oxygen in the soil water column.
