In Louisiana, most soybean varieties represent maturity group (MG) III and IV (indeterminate); and MG V and VI (determinate).
Flowering of indeterminate soybeans is initiated in the lower portion of the plant and proceeds upward; terminal buds continue growing several weeks after flowering. There can be considerable difference in seed maturity with bottom seed reaching maturity first. With the variation in seed maturation, indeterminate soybeans tend to retain leaf material and stems remain green later into the growing season.
In contrast, flowering of determinate soybeans is initiated in the middle portion of the plant and proceeds towards the top and bottom; terminal bud growth ceases when flowering begins. While there may be some slight difference in seed maturity on the plant, most seed mature at the same time.
For more, download Soybean Harvest Aids 2012.