Ideally to maintain maximum yield, extend the planting of your full-season variety up to June 10-15th. After that planting date window, based on our research, early and late varieties are the same in yield and that is why it is a good decision to switch to earlier maturity varieties to reduce the risk of a fall frost.
If you have growers planting long full-season varieties, the switch date could be closer to June 1st. And the decision process includes higher risks when considering that the soybean variety is Identity Preserved compared to Roundup Ready soybeans. Moisture at harvest and the risk of green seeds could be an issue if an early frost was to occur and are additional factors to consider.