Effect of Temperature during the Ripening Period on the 100-Grain Weight of Soybean in Shonai District of Yamagata Prefecture

Abstract

The relationship between 100-grain weight of soybean and temperature during the ripening period was analyzed by using crop data of soybean cultivar “Tachiyutaka” from 1989 to 2008 in Shonai district of Yamagata prefecture. The grain yield was correlated with the number of pods per unit area when the average number of pods was below 772 m^-2, and 100-grain weight when the average number of pods was over 772 m^-2. In addition, there was a significantly negative correlation between temperature during ripening period (from flowering stage to maturing stage) and 100-grain weight. The dry matter production of soybean plants from Aug.1 to Sept.1 decreased with decreasing daily temperature range from Aug.1 to Sept.1 resulting in a decline of dry matter production per pod and 100-grain weight. From these results, we concluded that the decline of 100-grain weight was caused by the high temperature during the ripening period in Shonai district of Yamagata Prefecture situated in the cold climate region.