Corn grain handling and storage

Encyclopedia Article

By Charles Hurburgh, Roger Elmore and Alison Robertson

19 Oct 2009 -

A three-part series of articles highlight current field conditions, test weight, weight shrink, field molds, and storage management for Iowa's corn crop. An abstract of each article is listed below with links to the extended articles, with several tables and decision tools.  

Overall Quality Issues

A cool, long growing season will often result in high yields with high grain moistures and low test weights. The lower test weight is the result of more starch and lower protein on a relative basis, a condition that also reduces field dry down rates and increases drying costs. The quick burst of heat in September moved many crops, especially in the western half of the state, to maturity at the further expense of some grain fill and test weight.

East of Interstate 35, corn ranges from the low 20s to mid 30s moisture. Some corn was frost-damaged at the half to three-quarter milk line. This corn will be low test weight (likely below 50 lb/Bu) with all the characteristics associated with low test weight.

Corn that has not dried early in the harvest period often stops at 17 to 18 percent. In 2008, this was in the 20-22 percent range. With the number of favorable drying hours much fewer after Oct. 20, attention needs to be given to stalk health. Producers may have to harvest wetter corn first if it is lodging.

Expect drying to cost about five cents per point of moisture removed. Eight points removed, down to 15 percent moisture, would cost about 40 cents per bushel plus the weight shrink. For this reason, there will be an incentive to hold corn at higher moistures, awaiting better drying conditions in the spring, blending opportunities, or higher moisture feeding. However, experiences from 2008 demonstrated the high risk in doing this, particularly when test weights are below 54 pounds per bushel (lb/Bu) after drying. 

Read the full article about test weight, weight shrink, and corn storability.

Field Molds

Cool wet fall conditions favor the development of ear rots caused by Fusarium spp.  These white or pink ear rots are often found in ear corn stored too wet. Field moistures in the low 20s over a long period can favor growth of these fungi, provided temperatures are warm enough (usually above 45F).  These fungi also can produce several toxins that harmful to people and livestock – vomitoxin, zearalenone, and fumonisin.  Grain with field mold should be tested for mycotoxins before feeding.

High moisture conditions favor growth of many ear and stalk rot fungi. Fields should be scouted as soon as possible to determine the extent of disease problems. To minimize losses due to ear rot and increased mycotoxin levels, it is recommended that producers harvest problem fields (greater than 10-15 percent incidence of ear rot) as soon as possible.

The longer the corn remains in the field, the greater the chance of toxin production. The toxins most likely to increase in the field at this time are those associated with Gibberella and Fusarium ear rots - namely vomitoxin, zearalenone and fumonisin. 
Read the full article, including tables.

Storage Management

There is less room to accommodate wet grain from this year because the grain market system is already overloaded with poor quality corn from 2008 crop.  However, we learned from 2008 – extra cost in additional handling and drying logistics is likely to pay off in terms of avoiding spoilage losses later on. This would not be a good year to take chances that wetter corn will keep and can be absorbed in the spring/summer.

Every action taken after harvest affects the ultimate length of time grain can be stored and the quality at the time of use. Always get wet corn into an aerated storage immediately. Holding wet grain, especially without aeration, shortens shelf life considerably.

Aeration Practice

Phase 1: Fall Cool Down
   • Lower grain temperatures stepwise 

         • October 40-45 F

         • November 35-40 F

         • December 28-35 F

Phase 2: Winter Maintenance

   • Maintain temperatures with intermittent aeration

         • January, February 28-35 F

Phase 3: Spring Holding

   • Keep cold grain cold

         • Seal fans

         • Ventilate headspace intermittently

Read the full article, including tables.
Charles Hurburgh is a professor of Agricultural and Biosystems (515.294.8629 and at

Roger Elmore is a professor of agronomy (515.294.6655 and

Alison Robertson is an assistant professor of plant pathology (515.294.6708 and 

Iowa State University Agronomy Extension Corn Production