The Korean Journal of Crop Science ISSN:0252-9777(Print) 2287-8432(Online) 한국작물학회지

Considering the threats of climate change, this study was conducted to investigate the influence of temperature and day-length on soybean growth and yield when sown late in comparison to the optimal sowing time in the southern region of the Korean Peninsula. Sowing was executed in 10-day intervals, including on July 1, 10, 20 and 30 and August 10, considering that the optimum sowing time of the three soybean varieties with different ecotypes is June 20. Emergence rates did not differ significantly between late-sowing and optimal sowing in all ecotypes; however, the number of days to emergence, flowering, and maturity was smaller after late sowing. A multiple-regression approach was used to test the effect of temperature and day length on the number of growing days after late sowing compared to the optimal sowing time. This analysis revealed that the number of days required from sowing to flowering was positively correlated with both day length and temperature, and the number of days from flowering to harvest was positively correlated with day length and negatively with temperature. A multiple regression equation can be calculated as follows: the number of days required from sowing to flowering (Y) = 3.177 + (0.030 × (sum of day length + sum of temperature)), and the number of days required from flowering to maturity (Y) = 20.945 + (0.021 × (sum of day length + sum of temperature)). Multiple growth parameters were significantly correlated with yield components, depending on growing days. Optimal sowing resulted in the best yield, while later sowing decreased yield compared to optimal sowing. To avoid a significant decrease in yield, early-maturing species should be sown by July 20, while late-maturing species should be sown by July 10.