Machines used for harvesting corn have gradually become more complex and more expensive. These devices have revolutionized farming, allowing farmers to harvest vast tracks of land quickly with only a few employees. This speed has led to bigger and bigger farms, with many smaller farmers having to sell land, giving way to the march of technology.
Combines, large machines that are used primarily to harvest corn on the stalk, are ideal for threshing and gathering corn stalks over a wide field. Some models are capable of separating usable parts from those that must be discarded. According to the website for the Environmental Protection Agency, many of these devices are self-propelled, meaning the machine has its own engine requiring a driver. Other types of combines must be towed or pushed by a tractor or other engine-baring piece of farm equipment. Combines are also among the most expensive pieces of farm equipment, with list prices generally over $300,000.
A maize sheller is another type of self-propelled corn harvesting machine. According to the website for the Food and Agricultural Organization of the United Nations, these devices are built of rows of three to six conveyors that harvest corn still on the stalk, strip the corn of its unusable components and spit them out through a cleaning sieve. The difference between this system and the combine is the maize sheller is specifically designed for corn and cannot be used with other smaller grain or row-style plants. Dry harvesting of corn generally occurs from October 7 through November 3, according to the EPA's website.
Forage harvesters are tractor-driven implements that chop and gather crops like corn without doing any of the separating like the other machines. These devices are quite powerful, with some using as much as 600 horsepower. Crops are usually harvested wet through September 1 and October 15 of each year when using this machine so as to promote the process known as ensiling, which is a form of crop preservation through anaerobic fermentation.