We are approaching the period of winter that will provide longer day length and the potential for warmer day-time temperatures. Grain storage specialists suggest that it is a good idea to step up monitoring efforts for grain stored in bins.

Monitoring stored grain is particularly important during late winter months as mild temperatures begin to warm grain masses. Grain harvested with lower test weights, lower protein content, higher moistures, and presence of mould at harvest all contribute to the increased concern. Immature, cracked and broken corn kernels are more prone to deterioration than good quality corn.

Check Bins Regularly

Stored corn should be checked frequently. Experts suggest that stored grain should be checked once or twice a week during the winter.2 Probe the grain at multiple locations in the bin to determine if any hard spots are forming. Look for signs of moisture such as:

  • crusting on the top of the grain due to sprouting or moulding grain
  • condensation on the bin roof
  • soggy surface corn due to condensation and moisture absorption
  • hot spots within the top few feet of the bin.

Smell the grain. A musty or mouldy odour indicates the beginning of a storage problem. A fermented or sour odour indicates a serious problem.

Store grain at cool temperatures (0 to –6° C).1 The temperature of the grain should be checked down to 2.4 meters (8 feet) below the surface in several areas of the bin with a grain thermometer attached to a rod or pole. Record results to compare with the next inspection. A thermometer can be left at an 2.4 meter (8 foot) depth to get weekly temperature checks.2

An increase in temperature and/or moisture may indicate a problem with mould growth. If temperatures in stored grain begin to rise noticeably, a hot spot may be developing. A rise of only 1.5 to 3.2° C indicates a possible problem.2 The aeration fans should be turned on immediately and temperatures checked daily in this situation.

If a problem is discovered, grain can be cooled by aerating. Mould growth and insect activity decrease rapidly as temperatures decrease to near freezing.

Use every opportunity to keep the grain cold. If the grain contains a higher moisture level and cannot be cooled adequately, additional drying may be needed to prevent it from going out of condition.

Removing some grain out of each bin is a practical idea. This will provide an idea of whether problems are starting. Higher moisture corn may have a tendency to bridge, and it is better to know and solve this sooner rather than later when grain may be heating rapidly.

Time to be checking stored grain quality 01

How Long Can I Store Corn?

Information developed by Dr. Ken Hellevang, North Dakota State University, provides an estimate of the allowable storage time (AST) a grower might expect.3 AST decreases rapidly at warmer grain temperatures (Table 1). As spring approaches and outside temperatures increase, be prepared to inspect grain more frequently. External warming of the grain from higher daily temperatures will normally be limited to less than a meter (a couple feet) near the bin wall and a meter (a few feet) at the top of the bin.

Aeration is key to grain storage as bin surfaces are warmed by outside air and sun. The temperature difference between the grain mass and average outside temperature should not exceed 5° C.4 This is due to convective air movement that may occur when areas of the grain mass are warmed. Moisture from warmed grain moves with convective air and can condense on cold surfaces.

Please contact your DEKALB® brand seed agronomist for more information and discussion regarding management of stored grain.

Is Your Corn Beginning to Mold In Storage? Below are some tips to help you check your bins for any spoilage or hotspots

  • Check grain bins on a predetermined schedule, ideally at least once a week
  • Smell the grain. If it smells mouldy, or rotten, take action immediately
  • Look for signs of moisture accumulation. This could be in the form of crusted grain near the top of the bin
  • Measure the grain temperature on a regular schedule, to make sure there are no hot spots, and keep a record
  • If temperature of the stored grain is increasing, turn on the aerations fans to drive out moisture and cool grain



Table 1: estimated Allowable Storage Time (days) for Corn at Different Moistures

Grain Temperature ©

Corn Moisture (%)



















Source: Hellevang, K 2011. Corn dying and storage tips for 2011. North Dakoda State University