Analysis of Agronomic Traits of Soybeans Adaptable to Northern Area of the Korean Peninsula

We have conducted this study to select soybeans adaptable to North Korea using growing degree days (GDD) as a heuristic tool. For analyzing climatic conditions, we assumed that climatic conditions of Longjing, Donggang, and Yeoncheon are similar to the Eastern Coast Northern Zone, Suyangsan Northern Zone, and Suyangsan Southern Zone in North Korea, respectively. The predicted days to flowering of 100 soybeans grown at Longjing, Donggang, and Yeoncheon were in ranges from 7/17 to 7/30, from 7/16 to 7/28, and from 7/30 to 8/10, respectively, while the last date of flowering for completely harvesting were predicted by July 12th, August 2nd, and August 11th, respectively. The predicted days to flowering using GDD were almost similar to the days investigated in the three fields. These results showed that GDD is highly effective in predicting development rates of soybean, such as days to flower­ing and days to maturity. Although most of the tested soybeans were difficult to adapt to Longjing, we selected 12, 15, and 16 soybean varieties/lines based on the predicted days to flowering and last date of flowering for completely harvesting and yield of the soybeans grown at Longjing, Donggang and Yeoncheon, respectively, for further analyzing effects of the regional characteristics on agricultural traits of the selected soybeans. The 100-seed weight and yield of the selected soybeans grown at Longjing was significantly low compared with those at the other locations. The results implied that the soybeans would be exposed to freezing temperature before R6 stage and the reduced size would contribute to soybean yield loss. Taken together, we concluded that Suwon212, Iksan13 and ‘Shinpaldalkong2’ which were stable in degree of lodging, 100-seed weight, and yield at Donggang and Yeoncheon could be adaptable to Suyangsan Northern Zone, and Suyangsan Southern Zone in North Korea.