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Corn+Soybean Digest

Wet Grain Causes Storage and Mold Concerns for Farmers

The wet conditions of the 2009 corn harvest presented unique challenges to farmers and, according to Richard Stroshine, an agricultural engineer at Purdue University, those challenges still have not come to an end.

"Because the harvest was so unique last fall, we were doing things that we hadn't done in a long time," says Stroshine. "We were harvesting corn a lot later, and at higher moistures and some of it had disease in it. Because of that, there is the potential for some problems to develop."

The higher harvest moisture content and ear rot damage make it likely there is more fine material in grain bins.

"Fine material tends to collect in the center of the bin when the grain is dumped into the bin, even with a centrifugal spreader, and those high concentrations can cause some real problems," Stroshine says. "Usually farmers want to aerate the grain to control the temperature and take the grain down to a cool temperature for holding it over the winter. Fine materials interfere with that aeration process."

One solution to the issue of fine materials is for farmers to core their bins – or remove the fines by opening the center wells of the unloading augers to start pulling the corn from the center.

"In bins with flat bottoms, the nature of the flow is such that most of the corn is pulled out from a little column above the unloading auger first – which is right where the fine material is concentrated," Stroshine says. "A lot of farmers already are doing that, but I want to make sure that everyone understands if they haven't done it already, they should do it immediately."

Another issue that can interfere with aeration is having corn peaked in the bins.

"If there's a peak in the bin, it's going to be right above the center core where there is more fine material, so that makes the aeration problem worse," Stroshine says.

Fine materials not only interfere with aeration, however. They also tend to contain more pieces of diseased or moldy kernels.

"If there was ear rot damage to the corn, there are generally higher levels of toxins in the fine materials than in the whole kernels," Stroshine says. "In a year like this, and especially if farmers have problems with ear rot, there is another advantage to getting rid of the fines. By getting rid of them the farmer can often, although not always, reduce levels of mycotoxins in their corn."

Stroshine also reminds farmers that it is essential to check the corn in the bins for moisture and mold problems.

"Most farmers probably are checking their corn, but again, I want to remind them that they need to be out there every couple of weeks during the remainder of winter, and when it starts warming up they need to at least be looking inside their bins every week," he says. "Do they smell anything unusual? Do they see any evidence of discolored kernels on the surface of the bins? Is there condensation on the roof or walls? Does anything look out of the ordinary?

"I've already heard of some farmers who have found a layer of moldy corn on the tops of their bins. It's still winter, which means there was a spot of wet corn in the bin. That wet corn starts heating up because of mold activity. Mold activity generates warmth and that warm air rises up to hit the cold roof of the bin. The combination of warm air and cold bin roof causes condensation, which drops back down to the surface of the grain. Since that re-wets the corn on the surface, it starts molding. Sometimes it can happen even if it's cold, because some fungi can grow on wet grain a few degrees below freezing."

Another reason to check bins, Stroshine says, is to make sure the corn is at the proper moisture.

"The corn may be wetter than the farmer thinks it is," he said. "I've heard of a couple of situations where the farmers thought they put the corn in last fall at 15%, and when they tested it recently they found out it's at 17%. In one case, the farmer had left the aeration fan running continuously through the winter, and it's possible that is what re-wetted the corn because high relative humidity in the air will give up moisture to the drier corn."

Stroshine says in situations like these where farmers can be tricked into thinking the grain is at a lower moisture level, it's good to remove the corn from the bin to market it, or at least get a moisture test to see what they're working with.

"Most farmers are aware that if they have wet corn in the bin, they need to market that before spring," he says. "We don't recommend that farmers carry corn over winter at moistures higher than 20% when they plan to finish drying in the spring. Even that is maybe pushing it a bit, because penicillium, which grows at lower temperatures, can start growing at 18%."

Finally, Stroshine recommends that if farmers have grain storage and quality questions, they call the department's Extension office at 765-494-1174, where they will be directed to either Stroshine or grain storage and quality specialist Matt Roberts. Questions also can be e-mailed to Stroshine at or Roberts at

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