Soybean Corner Articles

Indiana Prairie Farmer publishes a column written by Tom Bechman with the help of CCAs for CCAs and their clients. With permission from Prairie Farmer we are posting these Corn and Soybean Corner articles on the CCA website. Many thanks to the authors and the support of Indiana Prairie Farmer.

When will late-planted soybeans mature?

Soybean Corner: CCAs weigh in on how likely green stem syndrome is this fall. 
Jul 30, 2019
 
We planted all our soybeans in early to mid-June. How much later than normal can I expect them to mature this fall? Is this likely to be a fall with green stem syndrome? If so, should I start checking grain moisture before stems are brown?
 
The Indiana certified crop advisers panel answering this question includes Betsy Bower, Ceres Solutions, Terre Haute; Traci Bultemeier, Corteva/Pioneer, Fort Wayne; and Dan Ritter, Dairyland Seed, Wabash.
 
Bower: Because soybean growth and development are affected by heat unit accumulation and day versus night length, we may not see any particular soybean group mature much later than normal. With late-planted soybeans, we typically increase seeding rates to improve overall yield potential. That’s because most people have realized that we need to increase the number of plants if we want more nodes for more potential pods to improve overall yield when planting late.
 
It’s too soon to tell if we will have a fall with green stem syndrome. While green stem syndrome is often associated with several viruses, particularly bean pod mottle virus, it’s also been noted as being the result of insect damage from stinkbugs, bean leaf beetles, thrips and aphids.
 
In 2018, we had moisture stress after pod set that limited movement of the plant carbohydrate load to the beans during pod fill — leaving it in the stem and setting up green stem syndrome. So, there are several physical and physiological stresses that can lead to green stems. You certainly should monitor soybeans for grain moisture before harvest. However, that may not make harvest of green-stemmed beans any easier.
 
Bultemeier: Generally speaking, a three-day delay in your expected planting date results in a one-day delay in harvest. For example, if the expected planting date was May 1 and the actual planting date was June 1, a 10-day delay in harvest can be expected. 
 
Green stem has numerous causes and isn’t fully understood. Late planting and drought can be two environmental reasons to see green stem in a fieldwide or farmwide situation. A University of Kentucky study showed that reduced podding, a likely result of late planting or drought, reduced the source-sink relationship of the nutrients in pods versus the amount in the stem, thus causing long-term green stems.
 
While I can’t predict the future weather and environmental patterns from my office, it’s always a good idea to check grain moisture, even if the stems are visually green when a harvest calendar date is nearing.
 
Ritter: Late-planted soybeans can be expected to mature a little later, but not much. Remember, soybeans are photoperiod-sensitive, meaning reproduction is triggered by a short day when nights get longer. In other words, soybeans begin the reproductive stage based on increasing length of darkness. 
 
Based simply on late planting alone, I wouldn’t expect green stem syndrome. Other factors can influence green stem syndrome, and based on those, we may or may not have it this fall. I would start checking grain moisture before stems are brown simply to monitor the grain maturation process and help with harvest management.