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What is a Combine Harvester?

J.M. Densing
J.M. Densing

A combine harvester is a vital piece of equipment for the modern farm. It is a machine that aids in the harvesting of grain crops by combining three separate functions into one piece of equipment. The combine harvester performs the processes of reaping, threshing, and cleaning. This allows the crop to be harvested more quickly and efficiently, and enables farmers to harvest larger amounts. Some crops that can be harvested using this machine include wheat, soybeans, oats and rye.

The first process performed by the combine harvester is reaping, which is cutting down the crop for harvesting. As the combine harvester drives through the field, the crop is pulled into the harvester in the front section, called the header. From there it is pushed further into the machine by a slowly turning wheel called the pickup reel, which also holds the plants for cutting. The crop is then cut by the cutter bar, which has teeth that are sometimes called mowing fingers. These cut off the plant at the bottom near the ground.

A combine harvester aids in the harvesting of grain crops.
A combine harvester aids in the harvesting of grain crops.

Next comes threshing, which is the process of beating the crop to separate the grain from the rest of the plant. After the crop has been cut, it is transported further into the combine harvester by a conveyor belt and deposited into a threshing drum. Inside the threshing drum, bars beat and separate the tops of the plant, containing the grain, from the straw, or the plant stems. The straw is carried up out of the combine by straw walkers, while the grain falls down through a screen for further processing.

Early mechanical reapers harvested grain but couldn't thresh or clean it.
Early mechanical reapers harvested grain but couldn't thresh or clean it.

Finally the cleaning process is accomplished using air blown on the grain or plant. The plant sits on a screen and air is blown on it forcefully. This separates and blows away lighter bits of plant material, called chaff, which may still be clinging to the grain. The grain then goes into a collecting tank. When the collecting tank is full of clean grain, it is shot out of a pipe called an unloader, into a storage bin or trailer attached to the combine harvester.

Sometimes the combine harvester spreads the unwanted straw behind it as it moves through the field. Frequently though, the straw is collected and tied into bundles to be used for feeding farm animals or for bedding. Some combines are equipped with attachments that are able to perform this process in addition to reaping, threshing and cleaning.

Discussion Comments


That was not a combine; that is a baler machine. Combines are harvester machines and they only harvest the grain and collect it. Combines are much bigger than balers and balers usually need to be pulled by a tractor while a combine is self-propelled.


I'm surprised that no one mentioned that this is the latest edition to Facebook's "Farmville" game. People who play the game can now buy a combine harvester instead of having to make room for a tractor, harvester and a seeder.

Players buy a combine chassis and have to ask friends to give them combine harvester parts. Once they collect around 50 parts, the combine is done and they can use it.

It saves space on everyone's digital farm and the mini combine harvester is really cute. I would love to see a real one in person – they look like they have a lot going on at once.


My uncle has a soybean field and a combine harvester for gathering them. His harvester both picks and threshes the beans. He said that his harvester is designed to carefully separate the soybeans from their pods without breaking them.

It is amazing to watch the harvester clear such a large area at a time. It’s even more amazing to know inside of that machine, the beans are being taken from their pods.

He can harvest his entire field in a few hours. It would take weeks for humans to pick all those soybeans, and they would still have a messy field full of useless plants left behind. The harvester acts as a giant lawn mower, taking the entire plant.


There is a large farm down the road from me that offers hay rides, a pumpkin patch, a corn maze, and farm tours during the month of October. I took my children there for a day of fun and education, and they were fascinated by the combine harvesters.

During the farm tour, people get to walk down a wide trail made by combine harvesters through a wheat field. The tour guide tells the guests how the harvester works, and they get to watch one in action. He also stops at a parked combine and lets children examine it up close while it is not running.


I live near a large wheat field, and I have always seen big pieces of equipment out there that I assumed were tractors. I now think that they are combine harvesters.

I didn’t grow up on a farm, but lots of people in our community did. So I never paid a lot of attention when driving by the wheat field.

I guess I thought that the tractors cut down the stalks of wheat and took them somewhere else for processing. I had no idea that harvesters were capable of processing the wheat themselves while gathering more. That explains why we don’t have any grain factories around here.


I have seen a combine bundling hay. It was the coolest thing, because I didn’t know that it could do that.

My neighbor had a large field in front of his house with tall plants. The combine went out there, and it would travel a short distance and stop. I didn’t know what was going on until I saw a neatly rounded hay bundle pop out the rear of the machine.

The combine went all over the field, stopping at intervals to spit out the hay stacks. The ground looked so neat and clean when it was done, and I could even see deer running across the field.

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    • A combine harvester aids in the harvesting of grain crops.
      By: vschlichting
      A combine harvester aids in the harvesting of grain crops.
    • Early mechanical reapers harvested grain but couldn't thresh or clean it.
      By: Toniflap
      Early mechanical reapers harvested grain but couldn't thresh or clean it.