Abstract
Recently, the water table controlling system called farm-oriented enhancing aquatic system (FOEAS) has been introduced into paddy-upland rotation fields in various areas. However, the effects of underground irrigation by FOEAS for wheat have not been elucidated. According to the FAO manual, 450 to 650 mm of water is needed during the growing period of wheat. In Seto Inland Sea coast area, normal rainfall during wheat growing period is about 400 to 500 mm and irrigation is not practiced for wheat production. We studied the seasonal water needs of wheat by pot culture and necessity of irrigation in Seto Inland See coast polder. In potted wheat, water consumption per day was about 1 mm from sowing to early February and it increased to 8 mm in heading stage, and declined after the middle of ripening stage. The amount of water consumed during the total growing period and after the heading stage was 612 mm and 326 mm, respectively. In the experimental field, rainfall during the wheat growing period and after the heading stage was 338 mm (77 mm less than normal) and 72 mm (half of normal), respectively. Water table depth was 40 to 60 cm in non-irrigated fields and 30 to 50 cm in fields irrigated by FOEAS. There was no difference in wheat growth or yield between non-irrigated and irrigated fields. This is probably because water table was high enough to fulfill the water needs of wheat even in non-irrigated fields.