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Are the maturity groups you’re planting the right ones for your yield goal?

Soybean development and maturity is related to day length or, more specifically, duration of darkness. Growers plant a soybean maturity that develops based on the photoperiod when they farm, usually with a range of ±0.5. If their average maturity is a 3.0, for example, they may choose a range from 2.5 to 3.5 so the crop matures at different times. When deciding on the proper maturity consider the following.

1. Maturity of a soybean variety is the length of time from planting to physiological maturity (just prior to harvest). Maturity group zones were developed to define where a soybean cultivar is best adapted. The maturity group is determined by abiotic factors. The main factor is photoperiod, followed by temperature, age and other environmental factors. 
2. Shorter days trigger soybean development; however, when daylight increases (spring), development slows. Flowering will differ significantly due to photoperiod, which is a constant value for a specific time period, location and genotype.
3. More than 45 years ago scientists Scott and Aldrich delineated and published hypothetical optimum maturity group zones across the U.S. based on photoperiod.
4. In 2007 Zhang, et al. redefined the optimum maturity groups zones using yield variety trial data from 1998 to 2003. There were minimal changes for MG=0 to 3 and broader changes for the MG=4 to 6 adaptation zones.  
5. Maturity groups can range from earliest (0000) in the North (up in Canada), to latest (10), in the South. There are gradations within maturity groups formed by adding a decimal to the maturity group number (e.g., 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9). For example, a seed company may offer a soybean variety with a 3.8 relative maturity. 
6. There have been significant changes in soybean genetics (soybean oil profile, herbicide traits, yield), management practices (row spacing, seeding rates, seed treatments) and climate conditions. Based on research with current soybean genotypes, it is thought that the timing of flowering as well as the adaptability could be changing.
7.  Because there was a lack of peer-reviewed studies covering the U.S. soybean growing area, Spyridon Mourtzinis, John Gaska and Shawn Conley at the University of Wisconsin reevaluated maturity group delineations (image below) using data from 27 states and 312 sites. For more information, read Delineating Optimal Soybean Maturity Groups across the United States. 
8. If a variety is a late maturity and moved too far North, maturity is delayed, seedfill occurs during cool, short fall days, and frost may occur before maturity. If an early variety is moved too far South, it matures faster, and seedfill occurs during hot, dry July or August days.  -Either way, there is potential to limit yield.
9. Spread your risk with soybean maturities. For example, there can be a 5 to 7-day range between each maturity group. If possible, plant early, and choose a maturity group that reaches their physiological maturity (95% pods turn brown) just prior to a killing frost to optimize yield potential.
10. As you know, one of the Six Secrets listed by Dr. Below is to grow the fullest maturity for your location to optimize yield. If you are growing the fullest maturity that you can, you are already there. If you think you can grow a fuller maturity, it just might help to boost not only your yields, but also profitability. 

Stephanie Porter is a sales agronomist with Burrus^® Hybrids. She educates growers and Burrus staff on all types of pests, weeds, diseases and other agronomic issues that affect corn, soybean and alfalfa production. She is a 2017 Illinois Soybean Association CCA Soy Envoy.