Drying grain in the field or…?

Farm Forum

Ken Hellevang, Extension Ag Engineer at North Dakota State University, shares his expertise in grain drying and storage with many Extension personnel in the upper Midwest, and this column refers to his recent information. When corn reaches maturity, the moisture content of the kernel is generally between 30 and 35%. 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.

As Ken states, 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 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. I helped hand harvest a corn fertility research plot in Lyman County on October 9. The corn was mature, and shelling out several ears revealed the moisture content as 21%. I’m sure there are fields in the area that wetter and some drier.

While the price of corn and grain sorghum doesn’t generate enthusiasm among farmers to dry grain, field losses can 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. When considering leaving grain standing in the field to dry, 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.

The propane cost to dry grain (per bushel per percentage point of moisture) can be estimated by multiplying the propane cost per gallon by 0.02. One propane distributer reports propane at $1.60/gallon, which would translate to $0.032/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/bu for corn, $0.32/$2.50 = 0.128 or 12.8%. Leaving grain in the field due to field loss may impact crop insurance/yield history.

Remember that poly bags are a good storage option, but they do 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.

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. Adding heat does not permit drying wetter corn and only slightly increases drying speed.

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