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Stored corn worries

Stored corn worries

In-bin natural air drying may not have moved the drying zone all way through the grain.

The moisture of corn being stored in bin across the Northern Plains may not be as low as many farmers expect, says Ken Hellevang North Dakota State University Extension agricultural engineer.

Corn at moisture contents up to 20% was harvested and placed in bins with natural-air drying fans sized to provide an airflow rate of at least 1 cfm/bu. Even though the outdoor temperature and relative humidity across the Northern Plains were conducive for drying during October, the drying zone may not have moved through all the grain, he says.

The drying front in stored grain may not have moved all the way through the bin.

The estimated drying time for corn with a moisture content up to 20% is 30 to 40 days with an average air temperature of about 50 degrees F, about 50 to 60 days at 40 degrees F and at least 70 days when the air temperature is near 30 degrees F.

The moisture-holding capacity of the air at temperatures below 35 to 40 degrees F is small, so drying becomes inefficient using natural-air/low-temperature drying, he says.

Drying time also is related to the airflow rate, so at an airflow rate of 0.75 cfm/bu, drying time at 1 cfm/bu is extended from 40 days to about 53 days (40 divided by 0.75).

Warming the air by about 5 degrees F will allow producers to continue drying corn with the typically higher air humidity level that occurs in November, if the outdoor air temperature is averaging at least 35 to 40 degrees F, Hellevang says. Adding more heat causes grain in the bottom of the bin to dry to a lower-than-desired moisture content.

Use a bin-stirring device or do batch-in-bin drying with only a few feet of grain in the bin if the air is heated more than 5 to 10 degrees F.

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Source: NDSU Extension

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