Corn drying conditions look as if they will be great, but conditions can change quickly and you need to be prepared.
Ken Hellevang, North Dakota State University extension ag engineer, offers the following 10 tips on drying corn efficiently, especially when it gets cold and wet later in the season:
- Don't use natural air or low-temperature drying for corn with moisture contents of more than 21%. Natural air drying doesn't work well in late fall because the air's drying capacity is extremely poor at temperatures below about 35 degrees F.
- Cool corn to 20-25 degrees F when outdoor temperature average near or below freezing. Finishing drying in early April. Natural air drying will be the most energy- and cost-effective method of drying at that point.
- Limit the corn depth to 20 to 22 feet in bins to obtain the proper airflow rate for drying. An airflow rate of 1 to 1.25 cubic feet per minute per bushel is necessary to dry the corn before deterioration occurs.
- Turn fans off during extended periods of rain, snow or fog to minimize the amount of moisture the fans pull into the bin. Adding heat doesn't help dry wetter corn and increases drying speed only slightly.
- If high-temperature drying, use the maximum drying temperature that won't damage the corn. That increases the dryer's capacity (bushels dried per hour) and reduces energy use. Removing a pound of water will require about 20 percent less energy at a drying air temperature of 200 F than at 150 F. Follow the dryer company's recommendation, but generally, drying temperatures should be 210 to 230 F. "Be aware that excessively high drying temperatures may result in a lower final test weight and increased breakage susceptibility," Hellevang warns. "In addition, as the drying time increases with high-moisture corn, the corn becomes more susceptible to browning."
- To prevent corn from scorching or browning during drying, limit dryer temperatures. Exposure to drying air temperatures above 200 F for more than two hours likely will result in some browning. For corn with moisture contents of more than 30 percent, browning is likely. The drying temperature and length of time the corn is exposed to the heat affect the potential for discoloration. Producers report that softer, higher-starch kernels may have a higher potential for darkening. Try reducing the temperature to various levels to see which one works best, Hellevang says. Temperature reductions likely will need to vary for corn from field to field. A cross-flow dryer that moves corn from the inside to the outside of the drying column, varies the corn flow rate across the drying column or varies the corn's exposure to the drying air should be less prone to cause kernel discoloration. Decreasing the temperature in the lower portion of a multistage dryer also will reduce the potential for heat damage.
- Another way to reduce the heat damage potential is to dry corn to 20 percent moisture content instead of 15 percent. Evaporative cooling still occurs at the higher moisture content, and the kernels will not be exposed to the heat as long when corn is dried to the higher moisture content. This also reduces stress cracks and kernel breakage.
- Use combination drying to reduce heat damage. Dry corn at 28 percent moisture content to 20% using a high-temperature dryer and store it for the winter, then dry it to storage moisture in the spring using natural air drying or a high-temperature dryer. Darkening of the corn kernel during drying also can be a result of sugar in the kernels becoming caramelized. This is a sign that the corn's development wasn't completed. Corn can be discolored without being graded as dryer-heat damaged. Kernels damaged by dryer heat are almost entirely black.
- Use in-storage instead of in-dryer cooling to boost the capacity of high-temperature dryers 20 to 40 percent, reduce the risk of stress cracks and remove about 1 percentage point of moisture. In-storage cooling requires a positive-pressure airflow rate of about .20 cubic feet per minute per bushel to cool the corn in about 75 hours. Start cooling immediately after transferring the corn from the dryer to the storage bin to reduce the condensation potential. To further reduce condensation, cool the corn to about 90 degrees in the dryer before placing it in storage. Dryeration will increase the dryer's capacity 50 to 70 percent, reduce energy use about 25 percent and remove 2 to 2.5 percentage points of moisture, or about .25 percent for each 10 degrees the corn is cooled. Dryeration is moving hot corn from the dryer to a dryeration bin with a perforated floor, where it remains hot for four to six hours, then is cooled and moved to a storage bin. A tremendous amount of condensation occurs during the steeping and cooling process, so move the corn from the dryeration bin to another bin for storage to prevent spoilage.
- Remove debris that accumulates during drying. It is more critical when outside air temperatures are cold because condensation can develop on the dryer, creating a wet surface where debris can collect. The debris may reduce airflow through the dryer, decreasing the dryer's capacity and creating a fire hazard.
For more information about corn drying, see NDSU's grain drying website at http://www.ag.ndsu.edu/extension-aben/post-harvest.