2024 年 34 巻 S 号 p. 1-5
A subsurface irrigation system “OPSIS” (optimized subsurface irrigation system) developed in Japan is expected to have high application efficiency because percolation water from irrigation pipes is restrained by an impervious liner sheet installed under the irrigation pipes, and non-consumptive irrigation water is circulated and reused as irrigation water. This study aimed to clarify the water-saving effects of OPSIS while maintaining crop yield. In this study, sugarcane was cultivated in fields where OPSIS was installed, and soil moisture was monitored using soil moisture sensors. The fields were located on Ishigaki Island, Japan, which occasionally experiences drought, mainly during the dry season (from July to August), with highest evapotranspiration and low precipitation. The results showed that soil moisture during the dry season was maintained above the soil water content of the primary wilting point by a lower irrigation water supply than the recommended rate provided by sprinklers on Ishigaki Island. The sugarcane yields were also higher than the average yield on Ishigaki Island. These results confirm that OPSIS contributes to higher crop production with less irrigation compared with sprinkler-based irrigation.
