August 16, 2000

Each year grain farmers must make an important economic decision about the best time to begin the corn harvest. Should they let the crop dry in the field and risk potential excess harvest losses associated with poor weather, or harvest at a relatively high moisture level and dry it with heated air?

This year farmers are looking at lower grain prices and higher energy costs than those seen in recent years. So the natural inclination is to favor field drying, but where do these costs approach each other?

The answer depends largely on harvest capacity, dryer performance, the price of corn and drying energy (gas and electricity), labor costs and any equipment upgrades needed for the harvesting-delivery-conveying-drying system, said Sam G. McNeill, University of Kentucky Extension agricultural engineer.

Several factors can be involved, but the trade-off often quickly boils down to weighing the cost of excess harvest losses against energy costs for drying, he said. Excess losses are those incurred by leaving the crop to dry in the field and can be 2 to 8 percent above normal loss levels of 1 to 2 percent that have been reported for timely harvest.

Drying costs could vary greatly this season depending primarily on the price of LP gas — which has been reported to range between 50-cents and $1 per gallon.

McNeill has put together a table of information to help producers evaluate their harvest decision over a range of typical yield levels, harvest losses and corn prices at a fixed drying cost.

Using corn prices of $1.50 to $2.50 per bushel, values in the table can be used to compare the value of excess corn harvest losses to energy costs associated with drying the crop by 5 or 10 points of moisture.

At 75 cents per gallon for LP gas and 7 cents per kilowatt-hour of electricity, the energy cost for corn drying will run about 1.6 cents per bushel for each point of moisture removed.

For example, with a potential yield of 150 bushels per acre, excess harvest losses of 5 percent above "normal" losses of 1.5 percent and a selling price of $1.50 per bushel, the value of the 7.4 bushels per acre of extra corn left in the field is $11.08 per acre. Comparing this figure with the cost of artificial drying reveals that $11.22 per acre is required to remove 5 points of moisture from a bushel of corn, from 20 percent to 15 percent moisture content. So, the economics for this situation slightly favors field drying.

If corn harvest began at 25 percent moisture requiring 10 points of moisture removal, the cost for heated air drying would increase to $22.44 per acre, more than double the cost of drying in the field.

McNeill's figures reveal that field drying is highly favored for all yield levels and corn prices if harvest losses are no more than 2 percent above normal levels. Conversely, if harvest losses are much above normal, such as 8 percent, heated air drying is highly favored for 5 points of moisture removal for all yield levels and grain prices used.

But the price for corn must exceed $1.80 per bushel or harvest losses must exceed 8 percent before operators can afford to remove 10 points of moisture with heated air this season.

At an excess harvest loss of 5 percent, natural and artificial drying costs are virtually equal at all yield levels when corn is priced at $1.50 per bushel and 5 points of moisture are removed. Artificial drying is more favorable as grain price and harvest losses increase, but corn must sell for twice this amount in order to pay for the energy required to remove 10 points of moisture from the crop under this condition.

Factors that affect harvest losses are combine capacity, insect or disease damage, dryer performance and field dry-down, primarily determined by variety and weather conditions.

Under normal weather patterns, losses are generally lower during the early part of harvest. Extended periods of adverse weather can delay harvest, increase lodging and reduce yields and test weight considerably.

Drying costs may differ from farm to farm due to the use of a different fuel type, lower cost of bulk LP gas purchases, or use of high efficiency dryers.

The figures presented by McNeill point out that efficient operators who normally have low harvest losses should be able to wait until corn dries in the field this year to avoid the costs of drying with heated air.

On the other hand, operators who anticipate having high harvest losses should consider drying corn by at least 5 moisture points and maybe 10 points, provided they have the equipment in place to do so and corn can be sold near $2 per bushel. Operators who fall in between these extremes have a choice of waiting for the crop to dry by five points in the field or harvest quickly if weather threatens the crop.

Contact your county Extension agent for agriculture and natural resources for more detailed information on Dr. McNeill's cost comparison table.


Sam G. McNeill, (270) 365-7541 ext. 213