A corridor of the Midwest stretching from Nebraska through Iowa and into Northern Illinois has been receiving almost continuous rainfall for an extended period this harvest season. This pattern has made it difficult, if not impossible to harvest soybeans.

The current scenario doesn’t fit what we might think of as a typical situation of repeated wet/dry cycles where the soybeans get wet in a rain event, then dry out, rain again, dry, and so forth. The combination of rainfall, high soil moisture and high atmospheric humidity have prevented these beans from drying further since the first week or so of October. Field dry down will not happen as quickly as would be expected earlier in the season or during drier periods last month. Soybeans typically dry down to 12-13% or even quite a bit less with warm, dry weather. Now, however, soybeans are staying in the 14-16% range all day, and harvest will take longer once field work resumes.

The question growers face is – “What will we be dealing with when the crop finally gets fit to combine?” In the repeated wet/dry cycle situation, we would expect to experience pod shatter either prior to harvest, or at the combine head. Will current field conditions lead to more pod shatter? Anything that prolongs the time between crop maturity and harvest can lead to increased shattering of the beans from the pods. The longer a bean plant sits and dries down, the more likely its pods are to twist, pop open and drop their seeds. Even if they hold on to their seeds, opened pods can let in water and pathogens, which may affect grain quality and storability.

Lodging is a concern the longer a mature soybean field stands in soggy conditions. The soybean stalks have begun the process of decomposition, and the longer they are left in the field,  the more stalk quality will deteriorate and the greater the risk for lodging. Current forecasts predict continued storms, and heavy rains and wind can bring on even more lodging. Lodging not only slows harvest, it can further hinder the drying process. Lodging also can put pods and grain on the soil surface. This can allow pathogens access to the seed, affecting storage life and possibly causing dockage at the final market.

Shawn Conley, soybean specialist with the University of Wisconsin said, “Lodging is a concern, as is the dirt that will be on these lodged beans, so harvest will be dirty. Shattering may happen but the greatest risk for this is when we get in wet dry cycles accompanied by freeze dry cycles. I did see a few varieties that had severe SDS start to shatter so harvest those at-risk fields first.”

Charles Hurburgh, Ph.D., professor of Ag & Biosystems Engineering at Iowa State University said in a recent extension posting that soybeans don’t mold as easily as corn does, but that the predicted continuing rainfall may lead to what he refers to as gray beans, or beans that have molded in the field. He added that even back in 2009 there were few instances of moldy soybeans, but it is a risk associated with an extended wet harvest.

In July and August, we like to say, “Rain makes grain!” As we get deeper into October, I’m thinking most everyone is more of the opinion, “Rain, rain, go away!”

Two recent extension articles from Kentucky and Ohio also address the risk to grain quality with the prolonged wet weather and delayed harvest.

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About the Author: Kevin Nelson

Kevin Nelson is a certified crop adviser (CCA) and 4R Nutrient Management Specialist (NMS) serving the ag industry in north-central Illinois. Nelson received his CCA certification in 1994 and is a Senior Agronomist with Prairie Agronomics, his independent consulting firm. Nelson has a strong background in soil fertility and precision agriculture, and he is passionate about providing information and advice to help growers be more profitable and grow better beans.