Effects of illuminations at night on heading, yield, and its components in rice grown in the early season in Miyazaki Prefecture [Japanese]

摘要

Recently, the heading of rice grown in early season in the paddy fields near streets, roads, and stores with artificial light in Miyazaki was occasionally delayed because of illuminations at night, which became a serious problem in rice production. The objective of this study was to determine how illuminations at night affected heading and the yield and its components in rice (Koshihikari, Kirarimitazaki) cultivated in the early season. From transplanting to heading, the critical light intensities affecting the heading time office were 4 and 30 Lx in Koshihikari and Kirarimiyazaki, respectively, indicating that the delaying effect on the heading time of Koshihikari rice was more obvious than that of Kirarimiyazaki. When Koshihikari rice was treated from the 3rd to 18th day before panicle formation, the effect of treatment in this study was most significant and followed during the 2nd day before panicle formation to the 12th day after panicle formation. in From tillering to heading, with Koshihikari rice the critical light intensities were 6 Lx, the heading time was delayed by about 25 days, and plant culm height became longer in comparison with control when treated with the intensity of 117 Lx. When the time of illuminations was near the heading time of rice. the percentages of the ripened grains and yield tended to decrease. Furthermore. when the rice was treated from the 2nd day before panicle formation to heading, the yield of Koshihikari rice was lowest. As a result, Kirarimiyazaki could reduce the damages of yield in the early season in paddy fields near streets or roads with illumination at night because there existed a difference of the effect of illumination on growth of rice between Koshihikari and Kirarimiyazaki.