Effect of the Change of Weather Conditions after 1980 in Yamagata Prefecture on the Rice Growth at Maximum Tiller Number Stage

Abstract

The heading date of rice was advanced by increased temperature due to global warming. The degree of the advance differed with the prefecture and city in the Tohoku district. We evaluated the yearly change in weather conditions (temperature and solar radiation) from transplanting date to maximum tiller number stage since 1980, and analyzed the relationship between weather conditions and plant growth at the maximum tiller number stage by using “Sasanishiki”, at Shonai experiment station on the coast of the Sea of Japan, and at Murayama experiment station in the inland basin of Yamagata Prefecture. Weather conditions at both stations changed after 1980, i.e., at Shonai, the mean temperature rose, and at Murayama, solar radiation decreased. Plant growth at the maximum tiller number stage changed after 1980 at both stations, i.e., at Shonai, the maximum tiller number stage advanced, tiller number reduced, and dry weight increased, and at Murayama, the maximum tiller number reduced. At Shonai, the mean temperature showed a negative correlation with both the time of maximum tiller number stage and tiller number, and a positive correlation with dry weight. At Murayama, solar radiation showed a negative correlation with tiller number. Thus, in Yamagata Prefecture, the yearly change in weather conditions and plant growth, and the effect of weather conditions on plant growth varied with the location. However, at both stations, reduction in maximum tiller number resulted in reduction in the panicle number, which is a yield component.