Comparison of yield in Korean small seed soybean cultivars with main stem and branch production

This study was carried out to investigate the agronomic characteristics of late-planted small seed soybean cultivars and to investigate the effect of number of pods and seeds on main stem and branch against seed yield in Korea. Seed were sown at 17 June 2003 and 16 June 2004 with on a 60 cm row width and 10 cm plant space. The flowering dates in small seed soybean cultivars were on July 26 to August 7 and the maturing dates were on September 23 to October 9. The days of from planting to flowering date and to maturing date were ranged as 39 ∼52 and 98-114, respectively. There was a highly significant difference (r=0.686, p<0.01) between total dry matter (TDM) and LAI at R5 stage. The number of pods on 2 ^nd branch showed the highest value by 7.6, and followed by that of 3 ^rd, 1 ^st and over 4 ^th branch in this order. The seed yield varied from 168 to 289 g m ² and the average of all soybean cultivars was 225 g m ^-2. The relation between the seed yield and the days of flowering to maturing date was high significant difference (r=0.575, p<0.01) and there was a high significance difference (r= 0.781, p<0.01) between the seed yield and the days of planting to flowering date. The level of significant difference was higher in the period of vegetative stage than in the period of reproductive stage in small seed soybeans. There was high significance difference (r=0.556, p<0.01) between the seed yield and LAI in soybean cultivars. A range of LAI for optimal seed yield may be shown about 3.5-4.5 at R5 stage. Also, there was a relationship between the seed yield and the number of pods on 4 ^th and above branch but was no significant relationship between the seed yield and number of pods on 1 ^st branch. The correlation between the seed yield and the pods numbers showed the most value by 0.640 (p<0.01) on 3 ^rd branch, and followed 2 ^nd branch, and 4 ^th and above branch in this order. There was a high significant relationship (r=0.648, p<0.01) between the seed yield and the number of pods on total branch among 22 small seed soybean cultivars. However, the relation between the seed yield and the number of pods on main stem showed no significant relationship (r=0.089, ns). These results indicated that in order to optimal seed yield of late planted (mid-June) small seed soybean, soybean cultivars forming more pods on the 2 ^nd and 3 ^rd branch should be bred.