A combine is a piece of farming equipment which is designed to harvest, thresh, and clean grain as it moves through a field. Combine harvesters are capable of harvesting a large amount of a crop in a short period of time, reducing the overall cost for the harvesting process by making it more efficient. Many farms around the world use combines which range from high-tech computerized devices to more old-fashioned harvesters, some of which are animal powered, especially in developing nations.
The harvesting of grain crops has long been a time consuming and therefore expensive process. Harvesting starts with the cutting of the grain, which was traditionally stacked in sheafs which were collected by people who would thresh the grain, separating it from the inedible stalks, and then clean it, removing chaff and other particles which are not edible. In the 1830's, the introduction of early combine harvesters streamlined this process, contributing to the industrialization of agriculture around the world.
A typical combine has interchangeable headers which are designed for specific grains. The header for the crop to be harvested is fitted, and the combine is slowly driven through the field. As the combine cuts the grain, it pulls the grain into a giant hopper which feeds it into a threshing drum. The threshing drum pulls the grain out, allowing the stalks to settle back into the field, and then the grain is cleaned. The cleaned grain can be poured into bags, drums, silos, and other storage facilities with the assistance of another hopper.
Because a combine can perform multiple tasks simultaneously, it is extremely efficient. The speed of the harvest varies depending on the combine, the grain, and the skill of the operator. To a casual viewer, a combine might seem to be fairly slow moving, but the speed of a combine is actually quite remarkable when one considers that the machine is performing three tasks at once. Combines are one of the major tools of commercial agriculture, facilitating the harvest of grains like wheat, rye, oats, and corn and lowering the cost to end consumers.
Several companies such as John Deere specialize in the manufacture and sales of farm equipment like combines, along with replacement parts and additional headers. A combine can be a significant investment, especially for a smaller farm. In addition to being available new through specialty companies, combines can also be purchased used at auctions and through private dealers.