Abstract

The objective of this study was to better understand how the occurrence densities of ivy leaf morning glory (Ipomoea hederacea) reduce the growth and yield of soybean crops. In 2016, ivy leaf morning glory had an occurrence rate of 12% in 67 farmlands across Jeonnam province. In 2017, however, the ivy leaf morningglory occurrence rate had risen to 39% in 33 farmlands across Jeonnam province. Ivy leaf morning glory growth rate varied significantly from region to region. The differences in growth between areas may have been caused by variation in temperatures, the depths at which seeds had been buried or their dormancy period. Compared with the free weed control, the shoot fresh weight of soybean crops competing with ivy leaf morning glory was reduced by 12, 25, 39 and 50% in crops with ivy leaf morning glory densities of 1, 5, 10 and 20 plants per m2, respectively. Soybean yields were reduced by 30, 72, 86 and 94% in crops when ivy leaf morning glory densities were 1, 5, 10 and 20 plants per m2, respectively. The reduction in soybean yield can be attributed to reductions in yield components such as pod numbers, 100-seed weight and ripening rate. Our study clearly showed the capacity of ivy leaf morning glory for destruction in soybean crops, however, further studies are needed in order to determine new means of controlling this weed without damaging crops.