Sang-ouk Shin, Keum-yong Park, Tae-joung Ha, Sea-gyu Lim, Seong-hyu Shin, Duck-yong Suh, and Ho-yeong Kim. Yeongnam Agriculutral Research Institute, NICS, RDA, Naei-dong, Miryang-si, Gyeongsangnam-do, South Korea
In southern Korea, soybeans planted in May generally produce less seed yield than those in June, even if their dry matter accumulation is more. This experiment was carried out to find why soybeans show such paradoxical relations between dry matter accumulation and seed yield by analyzing canopy structures. Soybean(cv. Daepung, maturity group Ⅳ) was sown by four different planting patterns with same planting density(190,470 plants/ha) on May 15 and June 15. Dry matter(DM) and leaf area index(LAI) in R4 stage were higher, and yield was significantly lower in the soybean seeded in the May. But DM, LAI and Yield were similar among seeding arrangements. The ratio of sink to source in R4 stage was lower in the soybean seeded in the May. Moreover, the portion of non-assimilating organs such as petiole and stem was higher in the May seeding. Light extinction coefficient of soybean canopy in R4 stage was higher in the soybean planted in May than June. Also, the net assimilation rate(NAR) of the May seeding from R4- to R6 stage was nearly a half of the June seeding. These results indicated that the soybean planted on June had more effective canopy structure in light utilization.
