Keeping stored grain cool is important as outdoor temperatures warm, a North Dakota State University Extension Service agricultural engineer advises.

The allowable storage time is reduced by about half with each 10 degrees the grain temperature increases, according to Ken Hellevang, also a professor in NDSU’s Agricultural and Biosystems Engineering Department. For example, the allowable storage time for 18 percent moisture corn is about 200 days at 40 F, 90 days at 50 F, 50 days at 60 F and only 30 days at 70 F.

“Not only are daytime temperatures increasing, but the bin works as a solar collector,” he says. “This heats the grain to temperatures exceeding outside temperatures, particularly on the south side of the bin and on the top of the bin.”

He recommends producers run the aeration fans periodically at night or during the cool part of the day to cool the grain. The goal is to keep the grain temperature as cool as possible during spring, preferably below 40 degrees. Nighttime temperatures in March are typically below 30; in April, below 40. Even in early May, they frequently are below 45 degrees.

Aeration fans or ducts should be covered when not operating. The wind will push warm, moist spring air through the grain, warming it to near the daily maximum temperatures. Typical maximum temperatures in late March are in the mid-40s and increase in late April to around 60 degrees.

Hellevang also suggests checking the stored grain every two weeks. While checking on the grain, measure and record the grain temperature and moisture content. Rising grain temperature may indicate insect or mold problems. Insect infestations can increase from being barely noticeable to major infestations in three to four weeks when the grain is warm.

Grain moisture content must be low enough to prevent mold growth at summer temperatures. Corn needs to be dried to 13.5 percent to 14 percent moisture for summer storage. The moisture content required for corn at spring and summer temperatures is similar to that required for wheat.

Corn at moisture contents up to 21 percent can be dried using natural air drying if the system provides an airflow rate of at least 1 cubic foot per minute per bushel.

About five weeks of fan time are required to dry corn during April and May. Natural air drying should be started when the average outdoor temperature is about 40 degrees. The temperature may be about 50 during the day and 25 at night. Typically this occurs in early April.

Air holds very little moisture at colder temperatures, so drying is inefficient at cooler temperatures, Hellevang says.

For more information on grain drying, handling and storage, visit NDSU’s Web site at http://www.ag.ndsu.nodak.edu/abeng/postharvest.htm.

NDSU Agriculture Communication