Producers who have 1996 corn in storage will need to check bins at least once a week this spring to identify problems before they become unmanageable. The problem is with low test weight corn that was either slow to mature or did not fully mature before it was harvested last fall. Low test weight corn can take on moisture in storage, especially if not properly managed, and is twice as likely to spoil as heavier corn at the same moisture.

Last year, a late planting, wet spring, and cool summer slowed corn maturation, which resulted in low test weights throughout most of Iowa. Test weights averaged 54 lb./bu., compared to around 56 in normal years. Across northern and northeast Iowa, test weights averaged 50-52 lb./bu.

Even though low test weight corn with a high moisture content may have been dried to 13-14 percent last fall, its moisture content could be as high as 16-17 percent this spring. Low test weight corn is softer and will absorb moisture from the air and invite attack by fungi. It also breaks easily when handled.

All stored grain should be checked for test weight, if none was determined last fall, and for current moisture content. Take samples from both the top and the bottom of the bin. The difference in moisture content should be no more than two or three percentage points; otherwise, grain may be starting to go out of condition.

To check grain, follow these steps.

• Look for signs of moisture accumulation, such as crusted grain (usually at the top center of the grain surface); wet, slimy grain; ice or frost accumulation on the grain (especially under roof surfaces, hatches, and vents, or in cold grain near the bin wall, often on the north side), and heating.
• Smell the grain. A musty or moldy odor indicates the beginning of a storage problem; a fermented or sour odor indicates a serious problem.
• Use a long, slender rod to pinpoint problems. Poke into corn mass in several places to find hard, compacted, or moist areas.
• Record grain temperature. Attach a grain thermometer to the end of a metal rod to detect hot spots, or record temperature of the first air that comes through the grain. The thermometer can be left at an 8-ft. depth to get a weekly temperature check. A rise of only 3-4 degrees indicates a possible problem; monitor temperature daily.
• Enter a bin only if you know its history--when it was filled or unloaded--and when others know where you are.
• Always turn off unloading equipment before entering a bin.
• Watch for molds and dust inside the bin; you may need respiratory protection.

Recommended actions

• If moisture content is 16-17 percent, turn on aeration fans or deliver grain to an elevator for proper storage. Most elevators have pricing options, such as free deferred price, in which the owner pays no storage fee but takes the price at a later date. Be sure to operate fans long enough to cool all the grain.
• If moisture content is over 17 percent, dry corn immediately.
• Use test weight to determine how long you should keep corn. If grain test weight is less than 53 lb./bu., consider selling it before summer. If you can, sell lighter corn first because it will go out of condition earlier than heavier corn. Expect to experience more storage problems as temperatures increase.
• Keep separate corn with a test weight of 54 lb./bu. or higher. In a year in which much of the stored corn tests light, heavier corn may sell at a premium, especially later in the summer.
• Test mold grain for mycotoxins before feeding it to livestock.

For more information about checking bins, or how to handle a grain storage problem, contact your county ISU Extension office or field agricultural engineer in your area. A special fact sheet about the problem, Have You Checked Your Grain Bin?, SP-46 [1], also is available at county offices or the ISU Extension web site [2] under Latest News [3].