October 24, 2002

Ag Engineer Says Drying Grain in Late October a Challenge

As fall temperatures drop, the challenge of drying soybeans, corn and sunflowers is increasing, according to a North Dakota State University agricultural engineer.

Ken Hellevang of the NDSU Extension Service says the moisture holding capacity of air is directly related to the air temperature, so it will take twice as long to dry grain at 30 F than at 50 F.

"Freezing grain while it is in the field will not result in drying," Hellevang explains. Ordinarily when temperatures are freezing at night, and the air warms up about 25 degrees during the day, the relative humidity drops. "With this low humidity level and a nice breeze, grain dries well during the day," he says. This year, afternoon humidity levels have been much higher due to lower temperatures. This has resulted in very slow drying.

According to Hellevang, harvested grain can be stored during the fall and winter at relatively high moisture contents, corn at 23 percent moisture, if it is kept near freezing temperature using aeration. "The allowable storage time doubles for each 10 degrees the grain is cooled," he says. Aeration fans should be operated to cool the grain to near freezing as quickly as possible. The grain should be cooled to 20-25 F for storage.

"Soybeans should be drying to some degree in the field, but cold temperatures have slowed this process," Hellevang says. "Soybeans up to 16 percent moisture can be naturally air dried in a bin with an airflow rate of 1.0 cubic feet per minute per bushel." The expected drying time is usually three to four weeks but will take much longer this year due to cold temperatures. The temperature of a high temperature column drier should be limited because of the number of cracked beans increases at warmer temperatures.

Due to the cool temperatures, natural air-drying of corn will not be as effective this year. Corn can be dried with airflow in about 36 days under normal October conditions using an airflow rate of 1.25 cubic feet per minute per bushel and 70 days under normal November conditions. "Drying speed is primarily related to the airflow rate and final moisture content is related to the relative humidity which is reduced by adding heat," explains Hellevang.

It takes around 30 days for sunflowers to dry using an airflow rate of 0.75 cubic feet per minute per bushel under October conditions and 60 days under November conditions. The main concern when drying sunflowers in a high temperature dryer is to keep them and debris from becoming so dry that they combust or become a fire hazard. "Thoroughly cleaning the dryer periodically will reduce the risk of fires," Hellevang says.

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Contact: Kenneth Hellevang (701) 231-7243, kjh-eng@ndsuext.nodak.edu
Writer: Deana Oe (701) 231- 8371, deana.oe@ndsu.nodak.edu
Editor: Tom Jirik (701) 231-9629, tjirik@ndsuext.nodak.edu

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