Q: How do I go about selecting the correct soybean maturity? When my seed dealer talks about a mid-group three to a late group four I get confused about what that means.
A: Another great question. The numbers that your dealer is giving you refer to maturity range (adapted to your particular area). Like corn, the numbers indicate how long it will take for the plants to reach maturity. Unlike corn, soybean maturity numbers don’t indicate a number of days (based on Growing Degree Units or GDUs) until maturity. The soybean numbers take into account your region, when you plant, and the type of bean. It’s not necessarily that Asgrow beans, for example, mature faster than Pioneer beans, but they can. The bigger impact in terms of maturity comes less from brand and more from the difference between determinate beans and indeterminate ones.
Soybeans grown in North Dakota might be a maturity group .8, which start to set seed and mature rapidly, which suits a shorter growing season. In the Mississippi Delta area though, a 7.0 soybean would make more sense—a 7.0 bean takes longer to produce seed, which is fine in an area like the delta, where the growing season in long.
Selecting the best variety depends on your end goal. Here in North Central Kansas, we usually plant a 3.4-4.0 soybean, which generally accommodate the length of our season. Some producers though prefer a bean in the 2.8 range—they mature faster and so can be off the field faster to allow for the planting of wheat behind them. On the other hand, producers aiming for a double crop run can benefit more from a longer season bean (which is why dealers here typically have longer season beans on hand).