Except in Iwate prefecture, the percentage of first-grade rice grains was lower throughout the Tohoku region in 2010 than the average for the past 10 years. This study examines grain quality and factors affecting grain quality, with a discussion of methods to improve grain quality in the Tohoku region. The reason for the assignment of the second or lower grade was the presence of immature grains in Aomori and Akita, while in Miyagi, Yamagata, and Fukushima, the rice crop had many white-core and white-belly grains. The mean air temperature in the summer of 2010 in Tohoku was higher than normal by 2.3℃. The mean air temperature was higher than 26℃ in most of the main rice production areas, suggesting that high temperatures degraded the grain quality. In some cases, top-dressing was applied insufficiently because the shoots were longer than usual, which seemed to exacerbate the grain damage caused by high temperatures. Differences in grain quality among the six prefectures are apparently attributable to differences in the high-temperature tolerance of the main varieties in each prefecture as well as to differences in temperature. Moreover, the cumulative air temperature from heading to harvest in 2010 was much higher than 1200℃･day, reflecting a late harvest. Methods that improved grain quality include the use of high-temperaturetolerant varieties, late transplanting, top dressing, control of rice-ear bugs, continuous irrigation, late drainage, and harvest at the proper time.
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東北地域における2010年産米の品質低下要因と対策技術
tarc_report_No114p67-117p.pdf
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