Irrigation Scheduling to Control the Capillary Saltish Water Movement at Crop Fields Newly Reclaimed from the Sea

A substantial big reclamation project for agricultural production is currently taking place at Isahaya Bay, Nagasaki prefecture located in the southwest of Japan. To improve the soil physical properties, a large amount of gypsum was added to the original heavy clay soil. Also, leaching was conducted for several months using a sprinkler. Following these treatments, crops were planted, but saltish clay soils near the drainage pipes buried below 70cm from the soil surface are still probable to damage the crop growth. In this report, some trials to control the salt damages in crop production are introduced. First, the soil’s physical improvement processes from the first stage of reclamation to the present stage are introduced. Second, experimental and numerical studies on the soil water movement and salt movement in the cropped fields are stated. Third, the optimal irrigation scheduling to suppress the upward flow of saltish water in the draught condition is discussed.