2012 Volume 68 Issue 1 Pages 87-92
In 2010, the highest average temperatures on record were recorded throughout Japan. Consequently, rice suffered extensive high-temperature damage. Determining the relationship between the temperature of irrigation water under such weather conditions and the growth of rice in paddy fields is important for investigating measures to respond to global warming, which is expected to progress in the future. In this study, water temperatures were measured at the intake location of irrigation water from a river, in the agricultural water canals, and in rice paddies; furthermore, a questionnaire survey on the occurrence of high-temperature damage to rice was carried out, after the harvest, among rice farmers in southeastern Miyagi Prefecture. From the water temperature measurements, the water temperature in the surveyed area strongly depended on the water temperature at the intake source, that is, the river water temperature. From the questionnaire results, it was found that as the daily average water temperature rose under conditions of similar air temperatures in the area, the number of occurrences of high-temperature damage in the surrounding area tended to increase. Therefore, to avoid hightemperature damage to rice grain ripening, it is important to obtain water with a low temperature from rivers or reservoirs.
