Though the August rains provided some much-needed hope for 2016 soybean yields, there have still been plenty of pleasant surprises on yield monitors this fall.
“The soybean yields have been outstanding in almost every situation. There are a few areas that were dry and stressed but 80% to 90% of the territory I cover is seeing some of the most outstanding yields they have had in the history of their farming operations,” said Chasitie Euler, Pioneer account manager in Henry, Fulton, Williams, and Lucas counties. “We are approximately 40% to 45% wrapped up with soybean harvest. We are getting a lot done with this beautiful weather. Hopefully the rain will hold off so we can get a lot of these acres wrapped up.”
That does not mean, however, that the soybean harvest is free from challenges. Green stems have been a fairly widespread problem around the state, which has made for some slow going.
“We received a few comments about soybeans having mature pods, but the stems remaining green. Similar observations were made in 2012 — another dry year. Green stems on soybean may be a result of a source/sink problem. With the hot and dry conditions this year, pod set was likely reduced. With a limited number of pods (sink), there are fewer places for the plant’s photosynthates (source) to go,” wrote Laura Lindsey, Kelly Tilmon, and Andy Michel with Ohio State University in a recent CORN Newsletter. “From previously conducted work by Dr. Jim Beuerlein, when soybean pods were removed from a plant node when they first formed and started to expand, the leaf at that node stayed green after the rest of the plant matured. If all the small pods were removed from a branch on a plant, that branch did not mature. Further, if setting of pods were prevented on the main stem of a plant but pods allowed to develop normally on the branches, those branches matured normally while the main stem stayed green and held onto its leaves. Anatomical studies of the flow of carbohydrates within a plant show that each leaf fills the pods at its node only, but if all its carbohydrates are not needed at that node, the extra will move to the next lower node. Therefore, soybean plants digest their leaves, petioles and stems to complete the pod filling process and add a few more bushels per acre. If the digestion of plant parts is not needed to complete pod fill, then these plant parts remain green.”
Insect feeding can also lead to challenges with green stems on dry soybeans.
“Another possible cause of stay green syndrome might be stink bug feeding. As the bugs feed, they inject saliva, which may impact the plant’s physiology to remain green. In 2012, some acres of green stem were known to have stink bug infestations, especially along the edge,” the group wrote. “We have seen similar fields with stink bug pressure in 2016. To check for stink bug feeding, open a few pods and look for shriveled or flat seeds that may indicate stink bug feeding.”
In addition to green stems, soybeans have also been inconsistently maturing.
“I’ve heard numerous remarks such as ‘my 3.5 maturity soybeans will be ready before my 2.9 soybeans and I planted them at the same time!’ So why are soybeans maturing inconsistently?” said Luke Schulte, Field Agronomist, CCA, for Beck’s Hybrids. “The environmental conditions of this past season may be a contributing factor to the inconsistency in soybean maturity we are experiencing across our geography. Throughout much of Ohio, we experienced very hot and dry conditions during June and July. While some areas received very timely rainfall during these months, most areas — particularly the northwest area of the state — did not. Unfortunately, we entered the reproductive stages of our soybean life cycle at the same time we were experiencing the brutal conditions of late June and July. This meant that the dual stress of heat and/or drought caused tremendous stress in our soybean crops.”
Those tough conditions can impact maturities differently.
“Depending on maturity of the variety planted, the length of time it takes a soybean to flower and set pods will vary. For shorter season soybeans, that length of time is much more compact than mid- to late-season soybean maturities. Since we were enduring such extreme stress during this flowering and pod set time frame, the natural tendency of the soybean plant was to abort pods to preserve energy and survive.”
When most of the state finally received some relief in mid-August with some very timely and yield producing rains, it triggered the soybean plants to continue reproduction and further set pods.
“Later maturity soybeans were able to add more pods as they were not as far along in their development. Shorter season soybeans however, had a relatively low number of potential pods to be added to each plant due to their growth stage at that time,” Schulte said. “This inconsistency is a reflection of pods aborted or pods remaining on the plant. When pods and/or seeds are aborted, the plant redistributes sugars and nutrients (photosynthate) to the rest of the plant. This redistribution then causes an increase in the concentration of photosynthate in the remaining plant tissue (leaves, stems, branches). This results in soybean plants with significantly fewer pods having significantly more green foliage, meaning it will not ripen or mature as quickly. Higher stress areas within the same field that were more drought stricken (hills, sandy or gravel areas) more than likely aborted more pods when stressed than higher water retaining soils. In those areas, we are seeing slower maturation due to the sugar and nutrients being held in the stems and leaves with less pods present on those plants.
“This same scenario also occurred in situations where we are seeing 3.5 maturity soybeans ripen or mature faster than 2.9 maturity soybeans planted at the same time. The 2.9 maturity soybeans added fewer pods when the rains in early August came through compared to the 3.5 maturity soybeans. This was because the sugars and nutrients of these plants had to move to foliage, rather than pods, with fewer pods available.”