Abstract
We analyzed the state of gale damage of soybean in the Shonai district of Yamagata prefecture caused by typhoon No.15 and No.16 in 2004. The rate of soybean yield decrease in the Shonai district was lower than that of rice yield decrease. In general, the soybean yield was lower in the coastal area than in the inland area, and in the northern part than in the southern part of Shonai district, probably because the wind was stronger and more salt particles reached inland in the northern part. The leaves of soybean plants began to dehydrate immediately after exposure to salty winds of typhoon NO.15, resulting in shrinkage and browning, and then defoliation at an early stage. There was a significantly negative correlation between the distance from coastline and the degree of shrinkage and browning in the northern part of Shonai district. Spraying of seawater to the field significantly reduced the total weight at the maturing stage, number of ripening pods, number of ripening grains, yield and 100-grain weight of soybean. From these results, we concluded that gale damage caused by the two typhoons reduced the yield of soybean in the whole Shonai district, and that salty wind damage due to typhoon No.15 reduced the yield of soybean especially in the northern part of Shonai district.
