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Special Edition   April 20, 2009


Check Stored Grain Moisture Content

Moisture measurements at harvest may have been in error due to moisture gradients in the kernel, grain temperature, and other factors. In addition, the moisture may have changed while in storage due to moisture migration or moisture entering the bin. Collect and place a sample in a sealed container, such as a zip-lock plastic bag, warm the sample to room temperature, and then check the moisture content. If the sample is not warmed to room temperature in a sealed container, remember that the grain temperature needs to be above about 40 degrees and a temperature adjustment must be made either automatically or manually to obtain an accurate measurement.

Storing High Moisture Corn

Stored wet grain will rapidly deteriorate at warmer temperatures. Corn at 22% moisture has an allowable storage time (AST) of about 30 days at 50 degrees, 15 days at 60 degrees, and only about 8 days at 70 degrees. Therefore, corn at moisture contents up to about 22% moisture needs to be kept cool using aeration until it can be dried. Run the fans at night when outside temperatures are the lowest. Cover aeration fans when not operating to limit warm air blowing into the open fan and warming the grain.

Natural Air-Drying

Natural air-drying with an airflow rate of at least 1.0 cfm/bu can be used to dry corn at moisture contents up to 21% moisture during the spring. Start the fans when the average air temperature is about 40 degrees, which is occurring now. Drying time will be about 45 days with an airflow rate of 1.0 cfm/bu. The final corn moisture content will be about 13 to 14 percent.

Wheat at moisture contents up to 17% can be natural air-dried with an airflow rate of at least 0.75 cfm/bu. Start drying when air temperatures average about 40 degrees.

Storing Cracked or Immature Grain

Immature and lower quality grain is more prone to deterioration than good quality grain, so it should be dried to a moisture content about one-percentage point lower than good quality grain. It also needs to be monitored more closely than good quality grain.



Electric wiring, controls and fans exposed to water need to be evaluated and possibly reconditioned or replaced. Do not energize wet components. Be sure the power is off before touching any electrical components of flooded systems.

Grains swell when wet so bin damage is likely. Bolts can shear or holes elongate. Look for signs such as stretched caulking seals, misaligned doors or similar structural problems. A damaged bin is prone to failure.

Time is of the essence in salvaging wet feed and grain. Both will begin to heat and mold very quickly, leading to spoilage as well as the possibility of spontaneous combustion. Unloading from the center sump may not be possible because wet grain likely will not flow. One option is unloading the grain from the top using a pneumatic conveyor or other means.

Get the wet grain to a dryer quickly, if possible. This is the surest way to save wet grain. If the grain depth is only a couple of feet, a natural-air bin drying system with a perforated floor and a high capacity drying fan should be able to dry the grain. Verify that air is coming through the grain. Supplemental heat can be used to speed drying, but do not raise the air temperature more than 10 or 15 degrees.

If a dryer is not available, spread the grain to dry in a layer no deeper than 6 inches. Stir it daily to prevent overheating and to speed drying. Watch for and remove molded grains.

Do not feed heated, molded or sour feeds to livestock. Wet feeds should be presumed harmful to animals until tested. They may contain contaminants from floodwaters as well toxins produced by fungi.



Dry bales of hay should be removed and restacked in a dry location since capillary action will draw water up into the stack.

Flooded hay should be disposed of since it is probably unsafe for animals and not worth the time and expense of drying.

Because of hay's tendency to heat and mold quickly, it should be spread out to dry as soon as possible and turned often. Hay bales at 30 to 40 percent moisture content pose the greatest risk of spontaneous combustion. Check hay storage often for pungent odors, hot damp areas on the stack, emission of water vapors and other signs of heating. To check a stack's temperature for fire risk, drive a sharp pointed pipe into the hay, lower a thermometer inside the pipe and leave it there for about 20 minutes. At 150 degrees F, the hay is approaching the danger zone. At 170 degrees F, hot spots or fire pockets are possible. Have the fire department on standby.



Moldy grain and hay create a human respiratory hazard. Breathing mold spores can cause severe allergic reactions or other health concerns. Wear a mask or respirator approved to remove mold spores. The mask should have an N95 rating or better. These masks will have two straps.



Additional information is available on the NDSU Extension Service grain drying and storage website. Search for NDSU Corn Drying or go to

There is additional information on flood recovery on the NDSU Extension Service Flood Information web site. Search for NDSU Flood Information or go to

Ken Hellevang
Extension Engineer & Professor
Agricultural & Biosystems Engineering Department

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