The cost of producing corn is very high these days, and we can't afford to waste it in the field during harvest. We often harvest corn in a hurry because of threatening weather, shortage of harvesting machines, and other reasons without much thought to field loss. Then we see the stand of volunteer plants and wish more care had been taken to reduce losses.

Only a few of the factors in corn yield can be controlled, but harvesting loss is one of them. In corn yielding 140 bushels per acre, which is fairly common today, losses of 8 to 10 bushels per acre are fairly common, and may reach 20 bushels in lodged or weedy fields.

Field loss should be no more than 2 to 3 bushels per acre. Although it's difficult to achieve, losses can be reduced to less than 1 bushel per acre under good conditions.

Field losses have a very direct way of reducing profit. The grain you leave in the field will affect you first, reducing your bottom line income.

Losses cannot be eliminated, but may be significantly reduced if you take time to check your combine. To reduce losses, you need to know where they occur, how to determine loss levels, what “acceptable” loss levels are, and what adjustments and practices will help reduce loss.

Some corn is lost prior to harvest as ears fall because of reasons related to weather, cultural practice, variety, etc. These losses can usually be reduced by harvesting as soon after maturity as possible, not allowing the crop to stand in the field.

Corn that fully dries in the field will start shelling in the head rather than in the combine; the result is that kernels are lost before they even get into the combine. Corn that is allowed to fully dry in the field is especially vulnerable to loss.

Actual harvesting losses can be separated into categories. Pre-harvest losses are caused by pests, wind, wildlife, and other reasons. Gathering losses occur at the front of the combine, and consist of ears lost or partially shelled. Cylinder losses are seen on the ground behind the machine. Most are kernels attached to broken cobs that were incompletely shelled by the cylinder. Separator losses are kernels not separated from cobs and husks and discharged with the trash. Leaks result from wear and from failure to “button up” the machine completely after cleaning or maintenance.

Other losses come from spills while loading carts, trucks, and bins. Some are the result of using inexperienced workers, but most are caused by being in a rush to finish the job.

I am sometimes asked to go to a field and make an estimate of field loss. Producers and farm managers should do these estimates frequently themselves because conditions change throughout the harvesting season. One option might be to designate someone to do this job.

Losses are at times unavoidable as a result of field conditions, but these situations should be understood and evaluated, and losses should be kept to a minimum.

With corn selling at around $2.50 per bushel, reducing loss from 6 bushels per acre down to a more acceptable 2 bushels will be worth $10 an acre. That adds up to $1,000 on just 100 acres of corn. Large combines cover that much or more in a day. Most people can't afford to throw away $1,000 a day.

Measuring loss is simple, but time-consuming. This is the reason it is not done regularly.

The simplest way to estimate is to stake off a 1-foot wide strip covering the entire width of the combine head, and use colored ribbon or cord to mark the boundaries. Then search through the debris and collect the wasted kernels in the strip.

Two corn kernels per square foot in the strip equal approximately 1 bushel per acre loss. For a six-row machine in 38-inch rows, the strip will be 1 foot wide and 19 feet long across the swath. If you find 38 kernels, the loss level is approximately 1 bushel per acre; 76 kernels equals 2 bushels, etc. If you find more than an average of five kernels per square foot, a 2.5-bushel per acre loss, it's time to check for problems.


Ernie Flint is an area agent, agronomic crops, with the Mississippi State University Extension Service.