Harvest Technology

A machine to harvest the crop may be the most expensive piece of equipment that a farmer owns, and yet, for most of the year, it sits idle. Most farmers will still tell you that spending over a quarter of a million dollars on a combine is a worthwhile investment because you want to leave as little of your harvest in the field as possible. Harvest is where the work of an entire year or an entire lifetime comes to fruition.

In the around the turn of the new century, combines grew in size, sophistication and price – even though at a fundamental level, the functionality of a combine hasn’t changed since they were invented. First, a header has to cut the crop and feed it into the threshing mechanism. Second, the thresher uses some sort of mechanical beater to remove the kernels of grain from the straw and chaff of the rest of the plant. Third, a blower fan separates the heavier seeds or kernels from the lighter straw and chaff, while a system of sieves separate out larger dirt or debris particles. Fourth, a system of augers will deliver the grain to a holding bin and then to other vehicles to transport it to a harvest storage facility.

While the basic functions haven’t changed, the specifics have changed a lot.

Ag engineers have invented a plethora of different “heads” to pick up an amazing variety of crops, and deliver them to the separating mechanisms. One manufacturer boasts that they have machines that can harvest 80 different kinds of crops from the traditional grains to sugar cane (both green and burned), rice, forage crops, cotton, coffee, grapes, tomatoes and even berries.

Most combines sold are grain combines that can handle small grains to large grains (like corn) with relatively simple modifications. In 1975, New Holland introduced the first “rotary” combine. This new system used a helical rotating drum to do the initial separation of the grain from the rest of the plant. The rotor replaced the old system of rasp bars on the outside of a cylinder that rested in a concave base. International Harvester followed with their “Axial Flow” version of the rotor in 1977, and Gleaner came out with their N6 version in 1979. Other manufacturers followed with their own rotary designs.

In the 2000s, however, an increasing use of conservation tillage techniques led to a concern that the rotary harvesters were pulverizing the straw too much and leaving too little residue on the field. So, some manufacturers re-introduced conventional combines.

In the 80s, on-board electronics were introduced to measure threshing efficiency. Sensors helped the farmer know when the combine was letting too much of the grain slip through the threshing mechanism, and the operator could adjust the speed of the machine or other parameters. In the 2000s, GPS technology was added to combines to help position the machines and to keep track of how each section of a field was performing. These data could help the farmer adjust levels of fertilizer, pesticides or water for the following crop year.

Gravity has been the main force used in the threshing mechanisms of early combines, and designers have had to try to counteract the limitations of gravity. For instance, the wheat regions of the Pacific Northwest the soils are fertile but the fields are extremely hilly. In some areas slopes can reach 50 percent. On those hills, the grain would slip off the sieves of the threshing mechanism falling out of the combine onto the ground. Birds liked that, but the farmers didn’t.

So, innovative agricultural engineers designed machines that would level themselves. The cutter head would follow the contour of the hill while the threshing mechanism and operator’s cab stayed upright. In addition, rotary designs use centrifugal force more than simple gravity to separate the grains.

Farmers have found that the combines are cost effective, especially in crops that were labor intensive. For instance, the University of California-Davis studies the impact of rice combine technology on California growers. How rice has been harvested has a similar history as wheat or corn, so the study is instructive.

Initially, rice was harvested and threshed by hand. By the 1920s, the plants were cut and tied by a machine called a binder into bundles. A two- to three-man crew operated the binder. The bundles were stacked in shocks, where the grain was allowed to dry. A 20-man crew then transported the bundles to a central location where they were threshed by a mechanical thresher. According to the study, this harvest method required 4.5 labor-hours per ton of dry rice.

By the 30s, some farmers began using combine machines to pick up the swathed rice and thresh it. The combine unloaded to a tractor pulled bin and eventually delivered to a storage facility where it was dried. With this method harvest labor requirements dropped to 1.2 hours per ton.

By the 50s, combines were self-propelled and could be operated by a single person. Yields increased steadily as a results of hybrids and better nutrition and pesticides. In the 40s, yields were less than two tons an acres; by 1998 the yield was up to four tons per acre.

In the 90s, a stripper header became available that removed the grain from the straw without cutting the straw. This allowed the combine to be more efficient and to travel two to three times faster over the field. Average labor requirements dropped to only 1.5 hours per ton – from a high of 4.5 labor hours in the 20s.

If we translate those figures into economic terms, the study suggests that rice harvest costs have dropped from around 65 percent of total farm costs to around 18 percent today. Those results can logically be extended to any grain harvesting system – proportionally, farmers are spending much less of their total budget on the most important function of harvesting the crop.


York equipment dealer Jim Ermer knows first hand how harvesters have increased in size, sophistication and price. “In 1959, you’re probably looking at a combine [that cost] in the area of $55- to $60,000, depending on how you had them equipped, wholesale,” Jim says. “[Now] just a bare combine without the corn head, without anything else, is $250,000. Then you add another $60,000 for the corn head and another $30,000 for the platform… Bigger farmers. A lot less farmers.”


Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.

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