Effects of Temperature on Thousand Grain Weight in Rice Cultivation in Japan−Analysis Using Statistical Survey on Crops−

Abstract

Effects of temperature on yearly variation of rice thousand grain weight in 41 prefectures in Japan were analyzed for the last 19 years using the climate data published by the Japan Meteorological Agency and the statistical survey on crops published by the Ministry of Agriculture, Forestry and Fisheries. The temperature during the 4 weeks before heading in the 41 prefectures was from 20.6 to 28.8°C. In the 20 prefectures where the temperature during the 4 weeks before heading was less than 26.5°C , thousand grain weight tended to become smaller in the years when the temperature during the period was low. In the 6 prefectures where temperature during the 4 weeks before heading was less than 24.0°C, there was a high positive relation (p < 0.01) between temperature and thousand grain weight. This might be attributed to the small husk size due to the low temperature. On the other hand, in the 41 prefectures, the temperature during 4 weeks after heading was from 21.3 to 27.5°C. Then the relation between temperature during the 4 weeks after heading and thousand grain weight was not clear in most of these prefectures.