Corn reaching maturity about Oct. 1 will normally dry slowly in the field due to cooler outside temperatures. Standing corn in the field may dry about 1.5 to 3 percentage points per week during October and 1 to 1.5 per week or less during November, assuming normal Upper Midwest weather conditions.
ST. PAUL, Minn. (10/13/2014)—Corn reaching maturity about Oct. 1 will normally dry slowly in the field due to cooler outside temperatures. Standing corn in the field may dry about 1.5 to 3 percentage points per week during October and 1 to 1.5 per week or less during November, assuming normal Upper Midwest weather conditions.
Corn has a moisture content of about 32 percent when it reaches maturity. If it has a moisture content of 32 percent on Oct. 1 and we have normal weather, it may only dry to about 22 percent moisture by Nov. 1. As a general rule, field drying normally is more economical until mid-October. After that, mechanical high-temperature drying is normally more economical.
Cost, insurance factors
Growers who are considering leaving high moisture corn in the field to dry should make sure stalks and shanks are strong. Field losses can range from minor to severe. Compare the cost of drying versus losses associated with leaving the corn in the field. The propane cost per bushel per point of moisture removed can be estimated by multiplying the propane price per gallon by 0.02.
For example, the cost to remove 10 points of moisture using $2.00 propane is $0.40. Dividing the propane cost ($0.40) by the corn price ($3.00) provides the percentage of corn losses that will equal the drying cost. For example, $0.40/$3.00 = 0.13 or 13%. Also, verify the impact on your crop insurance on leaving the corn in the field.
Temporary storage considerations
Storage in a poly bag can be a good temporary option, but it does not prevent mold growth or insect infestations. Grain should be dry when placed in a grain bag. Higher moisture corn in a bag should be considered as very short-term storage and only at near-freezing temperatures. Ensiling may occur at moisture content exceeding 25 percent moisture and temperatures above freezing. This will prevent corn from being dried and sold in the general market.
Select an elevated, well-drained location and prepare the surface to prevent punctures in the storage poly bags. Run the bags north and south so solar heating is similar on both sides of the bag. Wild animals can puncture the poly bags, creating an entrance for moisture and releasing the grain smell, which can attract more wildlife. Monitor the grain temperature at several locations in the bags.
Natural air drying, holding corn over the winter
Because the drying capacity is extremely poor at outside temperatures below 35 to 40 degrees, little drying is possible using a natural-air system after November 1. The primary effect of adding heat during the drying process is to reduce the final corn moisture content. When outdoor temperatures average near or below freezing, cool the corn to 20 to 25 degrees for winter storage and finish drying in the spring (April to early May). Limit the corn depth to 20 to 22 feet so an airflow rate of 1 to 1.25 cubic feet per minute per bushel can be provided. This is necessary to dry the corn before deterioration occurs. Turn fans off during extended periods of rain, snow or fog in the spring to minimize the amount of moisture pulled into the bin.
High temperature drying
Using the maximum drying temperature that will not damage the corn increases dryer capacity. It also reduces the energy or propane consumption of a high-temperature dryer. Removing a pound of water requires about 20 percent less energy at a drying air temperature of 200 F than at 150 F. Follow the dryer manufacturer's recommendation; generally recommended dryer plenum temperatures are 210 to 230 F.
Excessively high drying temperatures may result in a lower final test weight and increased breakage susceptibility. In addition, high-moisture corn becomes more susceptible to browning as the drying time increases. A cross-flow dryer is more likely to maintain better corn quality if it moves corn from the inside to the outside of the drying column, varies the corn flow rate across the column, or varies the corn's exposure to the heated air.
Debris, mechanical damage
Condensation can develop in the dryer when outside air temperatures are cold, creating a wet surface on which debris can collect. It's critical to remove debris since it can reduce airflow through the dryer, decreasing its capacity and creating a fire hazard.
More mechanical damage to the corn occurs when harvesting high-moisture corn which affects its storage life. For corn that's low-test-weigh or has increased damage, dry it one percentage point lower in moisture content than normal. Check immature and damaged grain more frequently and do not put immature or damaged corn in long-term storage.
Finally, handling and storing high-moisture corn can be hazardous. Become informed of the hazards and recommended safety practices. Do not become a fatality.
Any use of this article must include the following credit line:
Information provided by Kenneth Hellevang, Ph.D., P.E., Extension agricultural engineer and professor of North Dakota State University. Additional information by Larry Jacobson, Extension agricultural engineer and professor University of Minnesota Extension.
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