Determinate cultivars planted in the southern U.S. begin to flower after the plant has reached its full height. Flowering begins at node 8 to 10 and proceeds upward and downward at a very rapid rate. Because of daylength requirement, Group V soybeans begin to flower earlier than Group VII cultivars. Planting a Group V cultivar late can result in a short plant due to early initiation of flowers. Late planting is more likely to be successful when later maturing cultivars are chosen, allowing more vegetative growth before flowering.
Final yield is primarily dependent on the number of seeds per pod and seed size.
Producers should be able to find small pods approximately 10 to 14 days after the first flowers appear. Fifty to eighty days are normally required for a flower to progress to a mature pod. However, this interval is highly variable between cultivars, environments, and planting systems. Seed dry weight accumulation begins about ten days after flowering and continues for four more weeks. References Carlson, J. B. and N. R. Lersten.