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Agronomy Update

Soybeans Not Fit to Harvest?

Published on Wednesday, September 28, 2016

“Harvest time is here but my soybeans won’t get fit to harvest!”

A very common, yet intriguing question many farmers have had this fall. 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? 

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 (in 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. 

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.

Most of the state finally received some relief around the second week of August with some very timely and yield producing rains. Those rains provided much needed moisture, which cooled our very warm soils and relieved our soybeans of some stress. They also triggered the soybean plants to continue reproduction and further pod set. Later maturity soybeans were able to add more pods as they were not as far as long 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. 

Now that our soybeans are beginning to reach maturity, many farmers are experiencing some inconsistencies. These inconsistencies have been seen not only among soybeans within the same fields, but also between maturities that were planted in the same time frame this spring. 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.  

If you have any questions, please do not hesitate to reach out to myself or your local seed advisor or dealer. Thanks and happy harvesting! 

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Luke Schulte

Luke Schulte

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