In the magical world of soybeans, most people have a basic knowledge of when the flowering starts. As soon as the days get longer, the beans start to flower. Right? But hold the phone, there’s more to it than that. Read on to find out what actually goes on and maybe how it can help explain why planting date is so important and maturities really matter.

Soybeans can begin flowering about a week before the summer solstice, but generally just after. This means that soybeans are photo period sensitive. They begin the reproductive stage when the nights become longer. They will put on viable flowers for about 50-60 days after. Early planted soybeans can actually start about a week before the solstice and carry through for about two months putting on flowers, that lead to pods, that lead to beans, that pays the bills. What does an extra few pods mean to yield?  Studies by Fred Below at the University of Illinois showed every extra pod you get, leads to 2 extra bushels¹.

Temperature is also key to driving flowering. Soybeans grow both reproductively and vegetatively through the summer. The warmer the temps, the more vegetative growth it gets, more nodes on the plant, that’s where the flowers happen.  In late planted areas, more vegetation is key. Whether that’s in the form of slightly longer maturities or higher populations, wave your magic wand and try to get the most biomass out there.

• What happens to the plant when planting is delayed? “Although soybeans respond to day length (photoperiod), flowering will be delayed past solstice when the crop is planted late. However, because it’s warmer, flowering will be faster which will compensate for the late start.”²

I wanted to look into that and found a research article from Iowa State University. In this test they did a five-year study using early soybeans (Group 2.2-2.7) and fuller season maturities (Group 2.5-3.9). They found that even though beans are planted late, the beans actually speed up the vegetative growth and mature at a similar time with earlier planted beans “In recent trials conducted at seven research farms over five years, the same soybean variety planted 40 to 60 days apart reached physiological maturity within 7-10 days of each other. Moreover, a 0.5 to 1.0 maturity group spread resulted in a difference of only 3-5 days to reach maturity.”³

Now did yield get affected? Of course, but changing maturities didn’t really make a difference in harvest date. But, we have to go with what mother nature deals out at the time of planting, Alakazaam! Good luck, be safe, and Happy Trails.

Cited Sources and Additional Information:

1. https://agfax.com/2015/07/09/soybeans-hold-pods-key-higher-bean-yields-dtn/
2. https://www.ilsoyadvisor.com/on-farm/ilsoyadvisor/agronomy-when-do-soybeans-start-flower
3. https://crops.extension.iastate.edu/cropnews/2019/05/late-soybean-planting-options

Download a copy of this technical bulletin here: Soybean Flowering