July 18, 2002

Barley Likely to Need Natural Air Drying

Harvested barley will likely require more natural air drying in the bin this year, says a North Dakota State University agricultural engineer.

"With short barley height in many locations we’re expecting more barley will be straight cut," says Ken Hellevang of the NDSU Extension Service. "As a result that grain is going to need additional drying."

Hellevang says the maximum safe moisture content for barley is 17 percent to assure that it drys before there is a loss in quality. A minimum airflow rate of 0.75 cubic feet per minute per bushel should dry the grain to a moisture content of about 12 percent over 20 days during late July and August.

Hellevang reminds producers that germination is critical for malting barley. "Mold will grow on the germ of the seed. That growth will affect germination before mold is visible and quality will be lost long before there is a visible mold problem," Hellevang says. The safe storage period, based on germination for barley at 17 percent moisture and a temperature of 68 F, is about 35 days and 19 days when temperatures are at 78 F. At 18 percent moisture, the safe storage period is about 26 days at 68 F, but only 13 days at 78 F.

Barley in a drying bin will be approximately the average of the daily maximum and minimum temperature plus about three to five degrees for the amount the fan heats the air. "The average temperature in July is 72 degrees, so if the fan heats the air about four degrees, the air temperature entering the bin is expected to be about 76 degrees. As moisture is evaporated from the barley in the drying zone the air will cool five to seven degrees, therefore the wet barley temperature above the drying zone would be about 70 F when the average outdoor temperature is 72 F," Hellevang says.

He notes that the resistance of airflow through barley is less than through wheat. "Natural air drying systems that provide an airflow rate of 0.75 cubic feet per minute per bushel through wheat should provide that amount of airflow or slightly more through the barley," Hellevang says. For example, an inline centrifugal fan providing 0.8 cubic feet per minute per bushel through wheat should provide an airflow rate of about 0.9 through barley. However, a high-speed centrifugal fan would be expected to provide the same airflow rate through wheat and barley because of its design.

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Source: Ken Hellevang, (701) 231-7243, kjh-eng@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu