The modern combine harvester, or simply combine, is a versatile machine designed to efficiently harvest a variety of grain crops.

The name derives from its combining four separate harvesting operations—reaping, threshing, gathering, and winnowing— to a single process. Among the crops harvested with a combine are wheat, rice, oats, rye, barley, corn (maize), sorghum, soybeans, flax (linseed), sunflowers and rapeseed. The separated straw, left lying on the field, comprises the stems and any remaining leaves of the crop with limited nutrients left in it: the straw is then either chopped, spread on the field and ploughed back in or baled for bedding and limited-feed for livestock.

Combine harvesters are one of the most economically important labour-saving inventions, significantly reducing the fraction of the population engaged in agriculture.

An early primitive combine was a horse-drawn “combination harvester–thresher” introduced in Michigan in 1836 and later used in California (see also thresher). Combines were not generally adopted until the 1930s, when tractor-drawn models became available. Self-propelled machines, capable of cutting swaths 2.5 to 5.5 metres (8 to 18 feet) wide, appeared a decade later. Originally designed to harvest wheat, they came to be used to harvest many other crops.

In design, the combine is essentially a binder-type cutting device that cuts and delivers the grain or seed crop to a threshing machine modified to work as it moves across the field. The cutting–gathering component, designed to take the grain with a minimum of straw, is sometimes called the header. A threshing cylinder rubs grain out of the heads against a concave surface. Some grain and chaff go with the straw to the straw deck, on which grain is shaken out and delivered to the cleaning shoe. Some of the grain and chaff goes directly to the cleaning shoe, on which sieves and a blast of air are used to separate and clean the grain. After passing through the air blast, the grain drops into a clean-grain auger that conveys it to an elevator and into a storage tank. Straw drops out of the back of the combine in a windrow for baling or is scattered over the ground by a fanlike spreader. Some combines for use on steeply rolling land have a body supported in a frame by hydraulic cylinders that automatically adjust to keep the body level.

A combine can be a very useful addition to your machinery set, particularly if your farm exceeds certain size and if you focus on certain crops. Different brands of combines have different specifications and different weights. Here are the specifications of some of the more popular brands:

1. John Deere S690 is a very popular offering from one of the most experienced manufacturers of agricultural machinery. This heavy-duty machine makes short work of dense, heavy crops while exhibiting exemplary performance in terms of speed and maneuverability. This machine’s weight (without headers) is 15,636 kg.

2. The Claas Lexion 780 is a popular German brand that exhibits exemplary performance and is popular across five continents. This machine is touted as being eco-friendly due to its environmentally advanced engine. Gleaning performance is enhanced by the fact that the sieve positions and fan speed adjust automatically as the machine moves over variable terrain. This machine weighs (without headers) 18,920 kg.

3. The Claas Lexion 795 is a more recent iteration of Claas machines. This limited edition machine stands out due to its unusual green and black paint job and its informal moniker “Monster Limited Edition”. This machine is similar in weight and other specifications to the 780, but it is touted as being superior in performance.

4. Case IH 9240 is a beautifully designed machine that is the most productive and powerful offering from Case manufacturing. It offers superior grain handling and the highest measured unload rate of modern combines. This machine (without headers) weighs 19,144 kg.