Managing Grain in Storage

Proper grain storage involves managing moisture, temperature, and insect activity in storage structures. Grain that has been damaged by insects may be more likely to rot in storage as the wounds created by insects are easy pathways for infection, and grain infected by ear molds is an obvious concern as the contamination can spread to other grain in the bin.


Grain moisture content. First and foremost, grain should be dried to the proper moisture content before storage to avoid grain quality issues (Table 1).

Tips to minimize contamination. Before storing grain, remove old grain and thoroughly clean the bin and surrounding areas. Ensure the bins are sealed from rodents or birds. Do not store new grain on top of old grain, mix new grain with old grain, or store grain in a dirty bin. Consider using residual insecticidal sprays to eradicate insects from the bin at least two weeks before storing grain, as well as insecticides to treat the grain as it is moved into storage.

Temperature (and uniformity) is critical. Low temperatures, 50°F and below, inhibit fungal and insect activity, so grain temperatures should be maintained as cool as possible in storage. Additionally, when the grain temperature in the bin is not uniform, moisture can migrate and accumulate in warmer parts of the bin, called ‘hot spots’, resulting in grain spoilage. Spoilage from moisture accumulation can occur at any time temperatures vary in the bin, but is more common when warm grain is stored and outside temperatures are cold. Regardless of the time of year, grain should be maintained within 15-20°F of the average monthly temperature.

Grain Storage

Table 1: Grain type, storage time, and maximum moisture content for safe storage

Aeration. Aeration is used to cool the grain in the fall, warm it in the spring, and homogenize the temperatures in the bin to avoid the buildup of moisture in hot spots. Ensure your aeration system is working properly before storage.

Monitor grain. When temperatures are quickly changing in the fall and spring, be sure to make weekly observations to grain in bins, especially when grain is above 55 to 60°F. This can be reduced to every two or three weeks throughout the winter. Keep an eye on the surface conditions, temperatures, grain condition, and be mindful of different smells, both in the grain and exhaust air. Grain that is crusting, wet, or slimy, as well as ice or frost accumulation and/or heating can be a sign of moisture problems and spoilage. Condensation or frost on the underside of the roof, hatches, and vents on cold days almost always indicate a moisture migration problem. If crusting occurs, stir the surface to break up the crust or if severe, remove the spoiled grain.

Once grain is cooled, continue checking exhaust air for smells regardless of the season or weather, if signs of heating are detected, run the fan continuously until no further issues can be detected. If hot spots cannot be remedied with aeration, grain may have to be removed, cleaned, dried, or even sold. It may be better to sell at a lower price than to allow an entire bin to go out of condition.


  • If you do have to store mold-affected grain, you will want to prevent additional mold growth on the stored grain by drying the grain down one point lower than the recommended normal moisture content – ideally at or below 14% for corn grain or 13% for soybeans.


  • Do not mix mold-affected grain or grain with heavy insect damage with clean grain or you risk contaminating the clean grain.
  • Sell poor quality grain first. Mold-affected and insect-damaged grain has a shorter storage life, even with careful management, and should be used early and first, leaving higher quality grain for longer-term storage.