Response of Soybean Varieties to Planting Densities

Abstract

The response of two determinate broad-leaf soybean (Glycine max.(L)Merr.) varieties Hualien No.1 and Tainun No.4 and one indeterminate narrow-leaf strain AGS62 to low (50x15 cm x 1pt/hill), normal (50x15 cm x 2pts/hill) and high (50cm, drilling) planting densities were evaluated at Hualien District Agricultural Improvement Station in 1982 and 1983. The leaf area index (LAI) of 3 entries reached the highest values at R4-R5 stage, and plant stopped growing at the same stage. The optimum LAI values for soybean yield were 4-6 for all the 3 varieties. Plant height increased with planting density largely by the increase in internode length instead of node number. As a result, soybean plants in the higher densities tended to lodge more easily. Varieties with vigorous branches such as HL NO.1 and TN No.4 produced 38-57% of the total pods in the branches, showing that the contribution of branches to grain yield was more important in this type of soybean. The results indicated the more the pods on branches, the higher the yield produced in soygean cultivar HL No.1. Since Harvest Index (HI) in this experiment was found to be highly significantly correlated (r=+0.731) with seed yield, soybean grown under favorable environmental conditions might get higher because of larger HI. Broad-leaf cultivars under low density (such as HL No.1 with density 13-14x10 pts/ha) and narrow-leaf under high density AGS62 with density 35-36x10 pts/ha) appeared to be a sutiable growthing conditions for getting higher yields.