That stuff coming out the back of the combine may be more than chaff – it may be income left behind during harvest.

Grain left behind in the field because of improperly operated or maintained equipment can cost farmers lost income.

A related factor farmers need to consider is whether to let the crop dry in the field or harvest it at a higher moisture level and dry it with heated air.

To ensure that the harvest loss due to equipment is minimized, farmers need to properly maintain their combine, said Sam McNeill, University of Kentucky College of Agriculture Extension agricultural engineer. Farmers need to be sure to set cylinder/rotors and fans to speeds suggested by the manufacturer.

Sanitation also is important to the integrity of the crop. All equipment that comes into contact with the grain should be cleaned prior to harvest.

After setting and cleaning the equipment, the next step is to determine when to begin the harvest.

This year, farmers are looking at more moderate energy costs and higher grain prices than in recent years, McNeill said. So, the question for the farmer is: What is the least cost option – field drying or drying with heated air?

The answer will depend on harvest capacity and efficiency, dryer performance, labor costs and equipment upgrades needed to do the job.

“Even, though several factors can be involved, the trade-off often boils down to weighing the cost of excess harvest losses against energy costs,” he said.

Excess losses are those incurred by leaving a crop in the field while it dries, and can be 2 to 8 percent above a normal loss level of 1 to 2 percent for a timely harvest.

Energy costs for drying will vary depending on the cost of LP gas, which has been found to range from 65 cents to 90 cents per gallon in a recent survey by McNeill.

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

To determine the best choice, a farmer needs to know his costs of drying and weigh that against losses if it is left to dry in the field.

For example, consider a potential yield of 150 bushels per acre, an excess loss of 5 percent to field dry the crop and a selling price of $2.50 per bushel. The value of the extra corn left in the field is $18.47 per acre. Compare that to a drying cost of $11.22 per acre to remove 5 points of moisture from the crop. In this scenario, drying with heated air is the most economical.But, if the corn had to be dried from 25 to 15 points of moisture, then field drying becomes more economical provided the crop can withstand the elements of nature.

Artificial drying tends to be more favorable as grain prices, yield levels and harvest losses increase, but at the 5 percent loss level corn must sell for $3 per bushel to pay for the energy required to remove 10 points of moisture from a crop.

A farmer can make his own calculations by using a spreadsheet developed by McNeill. This is the starting point for comparing the costs of field drying with those incurred by early harvest and artificial drying. Actual field losses can be measured by counting loose kernels in a harvested area. Two kernels per square foot is equivalent to a bushel per acre loss.

The spreadsheet and other information can be accessed via the Internet at www.bae.uky.edu/ext/GrainStorage.