October 3, 2008

Farmer Question: About how long should it take to dry 20% moisture corn to 15% using natural air during the last three weeks in October?

The High Plains Climate Center data for Lincoln shows the average 24-hour mean temperature is 51°F for the final three weeks in October. If we assume the mean humidity is 50% (dew point of 33°F) and if we assume the airflow is 1.0 cfm/bu, (the minimum recommended airflow for 20% moisture corn), we can estimate the time to dry this grain.

Under these climatic conditions, using the stated aeration fan, and assuming no stirring system in the bin, it should take about 20 days to bring the moisture content at the top of this bin of corn to 15%, assuming relative humidity of the exhaust air at 95%. It would take 27 days with an 85% relative humidity in the exhaust air.

If the bin is equipped with a stirring system, run the stirring system while filling the bin to relieve the pack factor, redistribute the fines (which tend to congregate in the middle of the bin) and level the grain. Then shut off the stirring system and allow a drying front to form and move through the grain. Since the bottom of the bin will be over-dried by the time a drying front is pushed through the bin, run the stirring system again when the top of the drying front is two feet below the surface to equalize the moisture in the grain mass. Using this stirring process could reduce drying time about three days.

Tom Dorn
Extension Educator, Lancaster County