Flooding and Stored Grain

June 22, 2011

By Charles Hurburgh, Department of Agricultural and Biosystems Engineering and Dan Loy, Department of Animal Science
Iowa is facing its third significant flooding situation in five years, which again raises the possibility of stored grain being inundated with floodwater. With only a few exceptions, flood soaked grain is not useable for feed or food. Iowa Secretary of Agriculture Bill Northey reminded farmers in a June 21 news release  that grain impacted by flood waters, whether in the field or in a bin, is considered adulterated and cannot be used for feed or food. Flooding affects both the stored grain and the storage structures. The best option is to move the grain before the flood reaches the bin, but stop using underfloor conveyors and legs once the water starts entering the pits.

Grain and Grain Products

Flood damaged grain is adulterated grain because of the potential for many contaminants to enter through the water. This grain should be destroyed, never blended. Contact the Department of Natural Resources (DNR) Environment Services regional office for the best disposal process in your area.
Water coming up from tiles and pits is just as suspect because storm and sanitary sewers are usually compromised in floods. Even field tile water may contain high chemical levels and other contaminants. 
Corn will stay at 30 percent moisture after the water drains off; soybeans about 25 percent moisture. The moisture won't travel more than a foot above the floodline.
Good grain on top of flooded grain must be removed from the top or side, not down through the damaged grain. The reclaim conveyors and pits under bins are likely to contain flood water as well. Remove all the good grain before doing anything with the bad portion. Do not start aeration fans on flooded bins.
Mold toxins are likely in rewetted grain. Warm wet conditions are ideal for mold growth. Soaked grain will spoil within a day or two at high moisture and summer temperatures.

Moldy grain is a safety hazard. The attached fact sheet prepared by the Iowa Department of Health for the 2010 flooding gives guidance on the hazards and protective equipment to use when working with moldy grain. Assume that flood soaked grain will be moldy by the time the water has receded enough to permit access to bins.

Take care not to track or mix mud or gravel from flooded grounds into good grain during salvage operations. These materials are potentially toxic for the same reasons as the floodwaters.
FDA allows for reconditioning (washing and drying at high temperatures) in cases where the flood water did not remain long and it is known that the water did not contain contaminants. This situation would be very rare, to know that floodwater was clean.  In both the 2008 and 2010 situations, the water was determined to be contaminated; expect that to be true in this case as well.


Grains swell when wet so bin damage is likely; more so with soybeans. Bolts can shear or holes can elongate. Look for signs such as stretched caulking seals, doors misaligned or similar structural problems.
Check bins with stirring devices carefully. The bin must be perfectly round for them to work correctly.
Bin foundations can shift, float or deteriorate from flooding. Inspect structures and foundations carefully, and have an engineering evaluation for larger bins.
Expect electric wiring, controls, motors and fans to be ruined. Do not energize wet components. Be sure the power is off and locked out before touching any electrical components of flooded systems.
Wood structures will be hard hit and may retain mold and contaminants.
Clean facilities and grounds completely. Then do a careful food safety inspection before returning facilities to operation. Maintain records of cleaning.


In the rare situations where the water was not contaminated, the grain may be reconditioned. If the grain is to be sold, reconditioning has to be done with the written consent of FDA. For feed on site, producers have three alternatives.

  • Dry the grain
  • Feed it immediately to their livestock
  • Ensile the grain for livestock feed.

Decisions need to be made quickly. The good grain should be removed immediately, again not down through the soaked grain. No flooded grain can be sold to the market without approval of FDA, to document its exposure only to uncontaminated water, with subsequent  reconditioning and intended use.
There is no problem, other than spoilage within a day or two, with using uncontaminated soaked corn as a livestock feed. Just replace the corn in the animals' current diet with the wet corn. Remember to adjust amounts fed for moisture.
Wet, whole soybeans can be fed to cattle if the soybeans are limited to 10 to 12 percent of the ration's dry matter. Soybeans substitute well for the protein in soybean meal, but they need to be fed with a vitamin-mineral-additive premix if substituted for a complete protein supplement.
It is not necessary to heat-treat the soybeans for cattle. Also, if adding whole soybeans to diets high in distillers' grains, watch the total ration fat content. For hogs, raw soybeans can only be fed to mature sows. The soybeans need to be heat treated if fed to younger pigs.

The Missouri River situation of 2011 is not likely to create salvageable situations.

Charles Hurburgh is a professor of Agricultural and Biosystems Engineering and professor in charge of the Iowa Grain Quality Initiative. Dan Loy is a professor of animal science with research and extension responsibilities for livestock nutrition.

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Charles Hurburgh Professor, Agricultural and Biosystems Engineering

Dr. Charles R. Hurburgh, Charlie to most everyone, is a native Iowan from Rockwell City (Iowa, USA). He continues to operate the family farm, and is a professor of Agricultural and Biosystems Engineering at Iowa State University. He has a bachelor's degree, master's degree, and doctoral degree fr...