Abstract
Subsurface irrigation system in paddy field is a system that can control the groundwater level by means of subsurface drains in paddy field, and their introduction into paddy fields is recommended by the Japanese government. Farm-oriented Enhancing Aquatic System (FOEAS) is one of the sub-surface irrigation systems, and case studies on FOEAS displayed the benefits of the system in terms of crop growth and changes in soil moisture. In a few studies, however, FOEAS was applied to rice cultivation such as the direct seeding cultures in paddy fields. In the present study, subsurface irrigation was conducted at the beginning of the rice cultivation period by v-furrow direct seeding. The changes of wetting area at the surface of the field were visually shown, and groundwater and the water budget were observed. The findings indicate that the wetting areas were distributed homogeneously by subsurface irrigation, and that the groundwater level rose inhomogeneously with the locations of observation points. However, invalid increase in irrigation without the valve closing and the automatic starting of irrigation needs further attention when the level of the level controller is set below the surface of the paddy field.
