The wet conditions of the 2009 corn harvest presented challenges for farmers and those difficulties still have not come to an end. This spring farmers in Iowa with corn stored in bins are being warned by Iowa State University grain quality expert Charles Hurburgh to check those bins once a week for signs of problems.

A farmer in Marshall County in central Iowa said his corn was just fine two weeks ago when he check his bins. But earlier this week he re-checked the bins and found a hot spot. The then got busy and rushed to move the corn—selling it before the damage got worse. It wasn't bad but it was heating up pretty fast and would deteriorate quickly if left in the bin.

"We are hearing about more of those situations every week as the weather warms up outside," says Hurburgh. Because the harvest was so unique last fall, farmers were doing things that they hadn't done in a long time. 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.

Accumulations of fines in stored corn can start hot spots

The higher harvest moisture content and ear rot damage makes 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. Farmers usually 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 the aeration process.

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

In bins with flat bottoms, the grain flow is such that most of the corn is pulled out from a little column above the unloading auger first, which is where the fines are concentrated. Many farmers are already are doing that, but if you haven't done it already, you should do it immediately, advises Hurburgh.

Having corn peaked in bins also interferes with aeration

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.

Fine materials not only interfere with the movement of air through the corn when you are trying to aerate the grain, notes Hurburgh, but the fine material also tends 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. 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.

You should check corn in bins for moisture and mold too

It is essential to check corn in bins for moisture and mold problems. Most farmers are checking their corn, but again,  we remind them that they need to be out there every week during late winter and into spring and when the days start warming up outside. You need to at least be looking inside the bins every week. Do you smell anything unusual? Do you see any evidence of discolored kernels on the surface of corn in the bins? Is there condensation on the roof or walls? Does anything look out of the ordinary?

Some farmers have found a layer of moldy corn on the top. That means there was a spot of wet corn in the bin during winter. 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 even if the temperature is a few degrees below freezing.

When checking bins, be sure grain is proper moisture content

Another reason to check bins is to make sure corn is at the proper moisture. Corn may be wetter than you think it is. There are 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.

In situations where you think the grain is at a lower moisture level and it turns out to be at a higher moisture level, it's good to remove the corn from the bin and sell it, or at least get a moisture test to see what exactly you are working with.

Most farmers know that if they have wet corn in the bin, they need to market that before spring. It isn'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 mold, which grows at lower temperatures, can start growing at 18% moisture content.

For more information, go to the Iowa Grain Quality Initiative web site at www.iowagrain.org