As early as 1928, engineers were experimenting with corn combines. But those first machines would choke on corn stalks if they tried to harvest any more than two rows at a time any faster than one mile per hour. Even at that impossible snail’s pace, the machine left up to half of the crop in the field instead of the grain bin.
The Gleaner-Baldwin company built the first technically successful corn combine in 1929. It used chains running in a ramp mechanism to gather the stalks and then cut them with pairs of circular saw blades. An auger mechanism fed the plants into a threshing cylinder. The machine lost only two to 15 percent of the harvest — depending on how wet the corn was, and that was one of the reasons the Gleaner combine didn’t sell well. High moisture corn was strong enough to survive the cutting and handling in the combine, but it was too wet to be safely stored. Corn kernels need to be below 14 percent moisture content to preclude rotting in a grain bin, and grain-drying technology didn’t really exist in the 1930s.
The other factor that hampered the first Gleaner combine was history — the Great Depression and World War II. First, farmers didn’t have the money to buy the new machines, and then wartime restrictions limited production.
After the war, the engineers got back to work. In 1954, John Deere became the first company to successfully offer a corn head unit that could be mounted on a combine. Their system was similar to the Gleaner design, but with just enough change to avoid patent infringement.
By this time, grain bins with aeration and heating units to dry the crop had been introduced. Deere and other manufacturers took advantage of this new technology and told their customers to harvest the corn with as much as 26 percent moisture and then dry it in the bins. The high moisture meant that the kernels stayed on the cob until it reached the thresher unit in the combine. Farmers could harvest a lot earlier than they used to be able to with corn pickers. So, they had a better chance of avoiding bad weather late in the fall.
The only downside was that the tougher corn stalks and higher moisture content required five time more power than grain combines. The corn combines had to have stronger grain bins and chassis to support the extra weight of the kernels. Gradually, stronger, more powerful machines were introduced, and then the race was on to build four-, six- and eight-row corn combines.
In later decades, corn heads reached 12-row spans and rotary threshing units used compressed air to more efficiently separate the corn from the chaff.