Measuring Harvest Loss: A Look Back, Look Ahead for Safer, More Precise Solutions

Harvest is a busy time of year, even if the weather is on your side. But let’s be real — the weather hasn’t been on anyone’s side this year. Living in South Dakota has been difficult with winds, rains, early snow, flooding, and a few tornadoes. It hasn’t been an easy harvest, but who would be surprised with the way this year started.


Weather isn’t your only adversary at harvest time. Perhaps the biggest challenger you face is also your biggest ally: your combine. In order to reap what you sow you need to pay close attention to your combine. If you don’t, it may be losing you thousands. I decided to do some in-depth research on this topic to gain some insight and historical perspective. Here’s what I found.

In general, harvest loss from your harvester can be anywhere from 1% to 10% of what is in the field. There are several factors to take into account, such as combine setting, harvesting speed, header height, reel speed, crop moisture, wind, and insects. All of these things can affect how much or how little of your crop is on the ground and not in your truck leaving the field. While we can only control a few of these factors, if we want to collect more crop, we need to find out how much is being left in the field.

There are several traditional tools you can use to help you determine your harvest loss, including hula hoops, PVC pipe squares, screens, shovels, and catch pans. During my research, I found a 1929 bulletin by the University of Minnesota titled “The Combine Harvester in Minnesota.” It describes how researchers used a blanket test to determine threshing loss. Here is an excerpt from the guide:

Threshing losses usually average slightly higher with combines than with threshing machines, owing chiefly to the inexperience of the combine operators. Practically the only grain lost in threshing is that carried Over because of too strong an air blast or too heavy a layer of straw and weeds, or in unthreshed heads.

During the harvest season, especially where combines are comparatively new, it is common to see men following the machine and looking for threshed grain carried over with the straw. If only a few kernels are found scattered along the ground it should not be considered a loss, as a bushel of wheat, for example, contains about a million kernels. All free grain found on the ground over which the machine has passed is not necessarily carried over with the straw or chaff-some combines allow a considerable quantity to escape from the feeder house and some may have resulted from shattering.

In straight combining the greatest threshing losses occur in lodged grain, when it is necessary to handle a large bulk of straw; and in weedy grain, which causes the machine to run slower. Under similar conditions with a windrower and pick-up outfit, losses are about the same as in straight combining. In a weedy crop, however, the windrow and pick-up method is better if the weeds are dry.

Blanket tests on machines in wheat showed threshing losses in straight combining as low as about o.1 percent and as high as 1.2 percent. When grain was threshed from the windrow, losses were greater than in straight combining. The highest single loss for this method amounted to 1.7 percent.

Grain Loss Indicator

Older methods of measuring harvest loss ranged from a Grain Loss Indicator from International Harvester (above) to a simple metal square (below).

Metal Square

The key back then was to study an area that could be easily calculated to scale findings to bushels per acre. Some of these older methods, which are still used today, make the math difficult. But if you build a frame out of PVC pipe or wood, and the internal area is 10 square feet, then the math is easier. For example, 20 kernels of corn found inside your frame would equal one bushel per acre loss. You can simply toss the frame into your harvested field and count the crop you find. This can be a pain and is difficult to get repeatability. In addition, you have no idea where that crop was lost in your combine. Was it it lost before you harvested that area? Was it header loss? Do you have leaks in your header housing? Or are these losses due to warn parts inside the combine?

If you had a method of tossing a pan while the combine is running that would make it possible to determine if the lost crop is coming from the discharge of the combine or header field loss. People try to do this with shovels. While walking next to the combine, they’ll attempt to catch the material coming out of the combine, which, if you value your eyes, lungs, ears, or limbs, is a dangerous idea for several reasons. Farmers need a safer solution to measure the harvest loss and I have had the opportunity to personally test one such solution.

Bushel Plus in Brandon, Manitoba, has been supplying remote drop pans for a few years now. This simple system uses permanent magnets to attach its receiver base (which covers and holds the drop pan) onto anywhere on the combine. While the rear axle is the usual mounting point, it can also be mounted on the feeder housing or crop head, according to Bushel Plus Technical Agronomist and Owner Marcel Kringe.

Bushel Plus System

The Bushel Plus system can be installed on many different brands of  combines.

Once the system is mounted you can operate your combine regularly, then when you want to collect a sample push the button on the remote fob. The next step is to clean the sample with the Bushel Plus Air Separator.

If you are looking for header loss look underneath the pan, that would have hit the ground before your pan dropped, but make sure you are only sampling from the same area as the pan, Kringe says. Now turn on the air separator and slowly speed up the fan, using your hand to slowly let the trash blow out the top. After that, pour the crop left in the bottom into the included scale. Then check the results by using the mobile app. Input your crop type, density, header width, the size of drop pan, discharge width, weight of grain loss sample, and your current yield. This will give you your loss in bushel per acre (the app also has metric settings) and your percent yield loss.

Bushel Plus Air Separator

The Bushel Plus Air Separator is used for fast, effective sample cleaning.

“Our system is four steps that could help you save $10,000 or more,” Kringe says.

The whole system is battery powered and in one afternoon I only used about 20% battery life. The battery is good for 120 pan drops on a full battery. The magnets are permanently charged so the system stays in place even if they battery is at zero. Each system comes with a wide and narrow drop pan for tall stubble, an air separator, a scale, manual, two remote fobs, and charging cables.

Looking back on older methods for measuring harvest loss gave me a greater appreciation how a newer solution can improve upon it. Harvest loss is an issue is as old as agriculture and can be frustrating unless it is measured more accurately and safely. Only then we can stop the crop thievery and get more to the grain bin.

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