Abstract
Continuous irrigation with running water (CIRW) experiments during nighttime were conducted in conventional paddy fields, to study the effect of nighttime CIRW on average water and soil temperature during 20 days after rice heading date and rice quality. By irrigations with total irrigation amount of 986 and 782 mm (123 and 78 mm per one time irrigation), 20 days average water temperatures after rice heading date were 2.3 and 2.2 °C lower at inlet of paddy field, respectively, and were 2.2 and 0.8 °C lower at center of paddy field respectively, than 20 days average air temperature. However, average water temperatures under the CIRW with 782 mm total irrigation water amount were lower near the inlet of paddy field, but higher near the outlet of paddy field, than those under conventional irrigation water management. Average water temperature and average soil temperature during 20 days after rice heading date showed almost the same temperature, and measurement depth did not affected average soil temperature. Ratio of chalky kernel under CIRW was lower than that under conventional irrigation water management during high air temperature condition, however that did not decreased by CIRW during low air temperature condition.
