Rising temperatures can cause mold in wet grain

Cattle Market & Farm Reports, Editorials
Feb 28, 2005
by WLJ
Stored wet grain will deteriorate rapidly as temperatures rise this spring, according to North Dakota State University Extension Service agricultural engineer Ken Hellevang.
Corn at 24 percent moisture has an allowable storage time of about 130 days at 30 degrees, but only 40 days at 40 degrees and 15 days at 50 degrees. Therefore, 24 percent moisture corn needs to be dried using a high-temperature dryer before the grain warms, Hellevang said.
The galvanized steel of a grain bin acts as a solar collector, so the grain near the south side and top of the bin will be heated to temperatures that exceed outdoor air temperatures.
Use aeration to cool grain that has been warmed during late winter or early spring, Hellevang says. Run the fan during nights or cool weather periods. The fans should be operated only long enough to cool the grain. To estimate the amount of fan time required to cool a bin of grain completely, divide 15 by the airflow rate. For example, about 75 hours of fan operation will cool a bin using an airflow rate of 0.20, but only about 15 hours is required using an airflow rate of 1 cubic foot per minute per bushel (cfm/bu).
Natural-air and low-temperature drying with an airflow rate of at least one cfm/bu can be used to dry corn at moisture contents up to 21 percent during the spring. Start the fans when the average air temperature is about 40 degrees. This normally occurs in early April.
Little drying occurs at temperatures below 40 degrees. Hellevang recommends that drying be completed by mid-May to prevent the grain from deteriorating near the top. Corn at 21 percent moisture has an allowable storage time of about 75 days at 40 degrees, 40 days at 50 degrees and 20 days at 60 degrees. The grain temperature will be near the average air temperature while fans are running.
Wheat at moisture contents up to 17 percent can be natural-air dried with an airflow rate of 0.75 cfm/bu. Normally, start drying in mid- to late April, when air temperatures average about 45 degrees. At 50 degrees, wheat at 17 percent moisture has an allowable storage time of about 130 days, and at 18 percent about 90 days. At 60 degrees, the allowable storage time of 17 percent wheat is about 75 days, and at 18 percent is about 50 days. Some of the storage life will have been used last fall, so the allowable storage time this spring will be less than allowable storage time charts indicate.
Immature and lower quality grain is more prone to deterioration than good quality grain, so it should be dried to a moisture content about 1 percentage point lower than good quality grain, Hellevang says. It also needs to be monitored more closely than good quality grain.
Stored grain should be checked every two weeks during the spring and summer. Remember to apply the temperature correction to moisture readings when checking the grain moisture content. If the grain temperature is below the operating range for the moisture meter, usually about 40 degrees, place the sample in a sealed container and warm it to room temperature before measuring the moisture content.
Grain should be kept below 30 degrees during late winter, and then below 40 degrees as long as possible. A 10-degree temperature increase cuts the allowable storage time approximately in half. In addition, insects are dormant at temperatures below about 50 degrees. Since a temperature increase may be an indication of grain deterioration or an insect infestation, check the grain temperature in several locations.
Aeration fans should be covered to prevent warm, moist air from being blown into the bin, Hellevang said. Since the wind blows more during the daytime than at night, the warm wind will heat the grain to temperatures near the daily high temperature if the fan or aeration duct is uncovered. This will increase the potential for insect infestation and grain spoilage. In addition, moisture from warm, damp air that enters the grain bin may condense on grain near the aeration duct or perforated floor. — WLJ