Grain frequently is stored short term in outdoor piles. However, precipitation is a severe problem in uncovered grain.
A 1-inch rain will increase the moisture content of a 1-foot layer of corn by 9 percentage points. This typically leads to the loss of at least 2 feet of grain on the pile surface.
A 1-foot loss on the surface of a 25-foot-high, cone-shaped pile is about 13% of the grain. This is a loss of $39,000 if the grain value is $4 per bushel.
If creating outdoor piles:
- Use a cover to prevent water infiltration. Aeration and wind blowing on the pile will not dry wet grain adequately to prevent spoilage.
- Prepare the ground surface where grain will be piled with lime, fly ash or cement to prevent soil moisture from reaching the grain.
- Place the pile so the storage floor is higher than the surrounding ground to minimize moisture transfer from the soil into the grain.
- Make sure the ground surface is crowned so moisture that does get into the pile drains out rather than creating a wet pocket that leads to grain deterioration.
- Examine the entire area to assure that flooding will not occur during major rain events.
A combination of restraining straps and suction from the aeration system holds grain covers in place. Place perforated ducts on the grain under the cover to provide a controlled air intake for the aeration system and airflow near the cover to minimize condensation problems.
Properly sized and spaced ducts also should be placed on the ground under the pile to pull air through the grain. If you use a perforated grain wall, the aeration ducts near the wall should not be perforated or the airflow through the grain will be limited to near the wall.
Cooling stored grain
Cool grain with aeration to reduce the insect infestation potential. Insect reproduction is reduced at temperatures below about 60 F, insects are dormant below about 50°F, and insects can be killed by extended exposure to temperatures below about 30°F.
Cooling grain as outdoor temperatures cool reduces moisture migration and the condensation potential near the top of the grain pile. In addition, grain moisture content and temperature affect the rate of mold growth and grain deterioration, with the allowable storage time approximately doubling with each 10-degree reduction in grain temperature.
The grain should be cooled whenever the average outdoor temperature is 10 to 15 degrees cooler than the grain. It should be cooled to near or below 30°F for winter storage in the northern states and near or below 40°F in states with warmer winter temperatures.
Aeration ducts need to have perforations sized and spaced correctly for air to enter and exit the ducts uniformly and obtain the desired airflow through the grain. The maximum spacing for aeration ducts is equal to the grain depth to achieve acceptable airflow uniformity.