Soggy Harvest

Rainy Fall Conditions Could Compromise Corn, Soybean Crop

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Soybeans that have dried down too long are vulnerable to shattering -- a phenomenon that occurs when the pod twists and pops open, exposing and sometimes dropping soybean seeds. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- Rainy weather across large swaths of the Corn and Soybean Belt is threatening to delay harvest and cause problems for growers.

Be on alert for stalk problems, grain quality issues and -- in the case of flooded fields -- the possibility that your crop is no longer food safe, experts told DTN.


Right now, the northwest and southeastern sectors of the Midwest are the soggiest, said DTN Senior Ag Meteorologist Bryce Anderson. Northern Iowa through south-central Minnesota as well as southeastern South Dakota received anywhere from five to eight inches of rain in the past two weeks, he said. Farther east, the Ohio and Tennessee valleys sopped up two to six inches of rain.

In the Southern Plains, southeastern Oklahoma and eastern Texas have also seen rainfall amounts ranging from two to eight inches, some of which drenched the northern Delta as well. And of course, the enormous rainfalls that North and South Carolina received from Hurricane Florence have flooded many crop fields.

Wet enough for ya? Brace yourself, Anderson said.

"That wet area of the northwestern Midwest will continue to be in line for rain, so I think that growers will continue to have a slower pace of harvest, and some crops could be knocked down by thunderstorm winds," he said. "It's also going to be cool which will slow down the pace of drying for fields to support machinery. Wetter areas of the Southern Plains will have less moisture over the next week, which will be favorable, along with a lighter precipitation outlook in the southeastern Midwest. The Gulf Coast and Deep South will have some heavy rain and there could be some damage to cotton with the bolls open and prone to damage from rain."


Wet fall weather often brings moldy corn ears to mind, but Shawn Conley would really prefer growers imagine shattered pods and flattened bean fields first.

"We really recommend you leave the corn and get the beans out first," the University of Wisconsin soybean and small grains agronomist said. Beans tend to be more fragile after they reach maturity than corn, especially if the grain is cycling between wet and dry conditions for a long period of time.

Shattering -- the soybean's mechanism for spreading its seed -- can be a problem during a delayed harvest. Although soybean breeders have worked hard to remove this trait from elite germplasm, the longer a bean plant sits and dries down, the more likely its pods are to twist, pop open and drop their seeds, Conley said. Even if they hold on to their seeds, opened pods can let in water and pathogens, will which will hurt grain quality, he added.

The longer a mature soybean field stands in soggy conditions, the more stalk quality will deteriorate and the greater the risk for lodging, which will drastically slow harvest. For help on harvesting lodged soybeans, see this Michigan State University article:….

It may seem to strange to talk about overly dry soybeans during a wet fall, but it is a risk, given how quickly beans can dry down, Conley added.

"Once they reach maturity, they can drop 8 points in a single day depending on winds and humidity," he said. Once soybean moisture drops below 10%, yield will fall, he added. A University of Nebraska study estimated that harvesting and selling soybeans at 11% moisture resulted in a yield loss of 2.25%. By 9%, that yield loss had dropped to more than 5%. (See the study here:…).

Given the dismal soybean price right now, many farmers may be tempted to store their beans for longer than usual, Conley noted. If you dry them down for storage, remember that mature soybeans are more fragile than corn and can be damaged by dryers, he said. "Depending on the dryer, you can really cause a lot of damage to that seed through the dryer's mechanical movement process and using too much heat," he cautioned.

See this guide from Michigan State University of how to safely dry and store soybeans in a wet fall:….


Now for the moldy corn ears. But first -- let's talk stalks, said Bob Nielsen, a corn agronomist with Purdue University.

"Once you hit maturity with corn, as stalk deterioration progresses -- which is just the normal decomposition that occurs -- the plant will simply get weaker and weaker and more vulnerable to any strong wind," he said. "That's my concern -- standability."

As they dry, corn husks may also pull back and expose the ear to the elements, namely rainfall.

"An extended wet period can lead to pre-harvest sprouting at the base of cob on upright ears or the tip of cob especially if tip kernels are damaged or have mold," Nielsen warned. Ear mold and injury actually change the hormonal balance of the kernels and prompt sprouting. See a University of Nebraska article on this phenomenon here:….

Even without sprouting, prolonged moisture can worsen mold problems and grain quality and leave farmers with a grain storage problem. See some tips from Purdue on storing moldy grain here:….

Like soybeans, corn left sitting in the field risks becoming too dry, even in a wet fall, Nielsen added. "If you're harvesting excessively dry corn, the risk of mechanical loss increases dramatically," he said. Overly dry ears can shatter as they hit the combine head, sending kernels flying. Overly dry shanks can cause ear drop to occur too easily, sending ears flying from the side of the header, rather than feeding in, he said.

"The sweet spot seems to be around 18% to 22% moisture for minimal harvest loss," he said.


When the clouds had finally cleared from Florence in the southeast U.S., many farmers were left with standing water and damaged crops. With heavy rainfalls forecast for parts of the Midwest and South in the week ahead, flooded fields remains a significant possibility for those regions, too, Anderson noted.

The situation prompted the Iowa Department of Agriculture to issue a release reminding growers that the Food and Drug Administration has a regulation in place to keep grain and other food crops that have been exposed to floodwaters out of the food supply.

Grain -- and any edible crop -- that comes into contact with floodwaters is considered "adulterated" and cannot "enter human food channels," the FDA states in its 2011 Guidance for Industry: Evaluating the Safety of Flood-Affected Food Crops for Human Consumption.

At issue are the pollutants that can come with floodwaters.

"In some areas, crops may be submerged in flood water which may have been exposed to sewage, chemicals, heavy metals, pathogenic microorganisms or other contaminants," the guidance reads. "Even if the crop is not completely submerged, there may still be microbial contamination of the edible portion of the crop. There is also the potential for plants to take up chemical contaminants. In addition to the direct presence of contaminants noted above, mold and toxins may develop in the crops as a result of exposure to the water."

Growers with flooded fields should reach out to their local state department of agriculture or crop insurer for help on how to proceed with evaluating those crops for food safety. See the FDA guidance here:….

Emily Unglesbee can be reached at

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Emily Unglesbee