Drying corn this harvest

Farm Forum

BROOKINGS — When corn reaches maturity, the moisture content of the kernel is generally between 30 and 35 percent. The time of year corn or other grain reaches maturity and the weather conditions can have a major impact on how quickly the grain will dry to a moisture content acceptable for storage or sale, explains Bob Fanning, SDSU Extension Plant Pathology Field Specialist.

He references Ken Hellevang, Extension Ag Engineer at North Dakota State University, and an expert in grain drying and storage for the information included in this article.

According to Hellevang, corn reaching maturity about October 1 will normally dry slowly in the field due to cool ambient temperatures. Standing corn in the field may dry about 1.5 to 3 percentage points per week during October and 1 to 1.5 percent per week or less during November, assuming normal North Dakota weather conditions.

“South Dakota conditions would be expected to allow the crop to dry somewhat more quickly,” Fanning said. “October 9, 2014 I helped hand harvest a corn fertility research plot in Lyman County. The corn was mature, and shelling out several ears revealed the moisture content as 21 percent.”

Fanning added that there are likely some wetter and drier fields in the area.

While the price of corn and grain sorghum this season doesn’t generate enthusiasm among farmers to dry grain, Fanning said field losses can still make it a smart choice.

“Hellevang suggests that field drying is normally more economical until about mid-October, but if the crop remains wet after that, mechanical drying with added heat can be well justified,” he said.

When considering leaving grain standing in the field to dry, Fanning reminded farmers to make sure stalks and shanks are strong. “Some extent of grain sorghum lodging is being reported, and the moisture during the growing season has caused a fairly high incidence of phomopsis in sunflower, which can result in lodging,” he said.

Calculate costs

The propane cost to dry a bushel of grain one percentage point of moisture can be estimated by multiplying the propane cost per gallon by 0.02. One propane distributor reports propane at $1.60 per gallon, which would result in $0.032 per bushel per point of moisture or $0.32 for 10 percentage points.

By dividing the propane cost to dry grain by the grain price, you can calculate the percentage of grain loss that will equal the drying cost. Using $1.60/gallon for propane, and $2.50 per bushel for corn, $0.32/$2.50 = 0.128 or 12.8 percent. “Leaving grain in the field due to field loss may impact crop insurance/yield history,” Fanning said.

Poly bags are a good storage option

Remember that poly bags are a good storage option, but Fanning said they do not prevent mold growth or insect infestations. “Grain should be dry when placed in a grain bag if it is intended to be marketed or stored as grain. Storing grain in a bag at moisture contents above the recommended levels for short-term storage should be considered very short-term storage and only at near freezing temperatures,” he said.

The recommended moisture levels for short-term storage vary by commodity and are as follows:

• corn – 15.5 percent

• grain sorghum – 13.5 percent

• non-oil sunflower – 11 percent

Fanning added that high moisture grain can be stored in polybags, but the grain will go through the ensiling process and its use will be limited to livestock feed. High moisture corn should be harvested between 24 and 33 percent moisture.

Corn above 21 percent moisture should not be dried using natural-air and low-temperature drying to minimize corn spoilage during drying. “Because the drying capacity is extremely poor at temperatures below 35 to 40 degrees, little drying is typically possible using a natural-air system after about November 1,” he said. “Adding heat does not permit drying wetter corn and only slightly increases drying speed.”

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