Sam McNeill
Extension Agricultural Engineer
University of Kentucky

Many corn fields in western Kentucky suffered unusually high wind damage from the remnants of Hurricane Ike this past Sunday, leaving most farmers in the region with questions about the best approach to this year's harvest. Much of the corn was well past physiological maturity, waiting for field drying under normal weather conditions before harvest began. Lodged and/or down corn dictates slow ground speed at the least so the combine can gather as much of the crop as possible. Still, harvest losses can be as much as 10-15% because most losses are from whole ears that can not be picked up by the combine. 

To worsen the problem, both liquid propane and natural gas prices have escalated from a year ago. A quick survey of LP gas prices in western Kentucky showed a range from $2.20 to $2.30 this year, almost $1.00 higher than prices a year ago, with natural gas prices also higher. 

On the positive side, weather conditions should be excellent for field drying during the remainder of this week with sunny daytime temperatures in the low 80's and night time temperatures in the mid-50's. Another positive is that most fields are dry, which means the corn root system will act as an anchor to hold the plant in place during harvest, allowing the stalk to be fed into the combine albeit under slow ground speed. 

In a typical year, the decision of when to harvest corn largely depends on the cost trade-off between excess harvest losses and energy costs for drying. Excess losses are those incurred by leaving the crop to dry in the field. With timely harvest, field losses can average 2 percent of the yield. As the crop remains in the field longer, losses normally increase to between 5 to 10 percent of the yield. 

To evaluate harvest decisions for wind damaged fields, producers need to look at expected yield levels, excess harvest losses during field drying, their contract or selling price for corn and a fixed drying cost for their system.  For example, consider a potential corn yield of 150 bushels per acre, harvest loss of 5 percent and a selling price of $5.50 per bushel. The value of the extra corn left behind in the field (7.5 bushels) is $41.25 per acre. Comparing this figure to the cost of heated air drying (with LP gas at $2.25 per gallon) shows that $29.57 per acre is needed to remove 5 points of moisture from a bushel of corn, but $59.14 is needed to remove 10 points. So, the economics for this situation favors heated air-drying (by $11.68 per acre), if less than about 7 points of moisture are to be removed. 

Now consider the same yield and price levels if excess harvest losses are above average, say 10 percent. The second table shows 15 bushels left in the field, at a value of $81.50 per acre, which compares to a drying cost of $56.03 for drying 10 points, or $84.04 to dry 15 points. 

Finally, consider a "worst case" scenario at the same yield and price levels where excess harvest losses are 15% and down corn is as high as 30 percent moisture, the cost of harvest losses would be $123.75 per acre but only $79.37 would be needed to dry the crop, so even at this high moisture the savings would be $44.38 per acre. 

Examples shown in the tables illustrate the impact of harvest losses on potential profit from the corn enterprise in wind damaged fields. Specific cost comparisons between field drying and heated air drying can be made with a spreadsheet tool available at the UK Biosystems and Agricultural Engineering Department.

Table 1. Cost comparison ($/ac) between excess corn harvest losses and heated air drying for different yield levels with different grain prices and energy costs to remove 5, 10 or 15 points of moisture with an LP gas price of $2.25 per gallon.