Round baler

How it works

A pickup at the front, a reel of spring tines on several bars, lifts the crop from the row and feeds it to a rotor. Many balers then push it past a bank of knives that chop it shorter, which helps density and makes feeding easier. The crop enters the bale chamber, where rollers or belts keep turning it so it builds into a roll.

When the bale reaches the set size the monitor tells the driver to stop. Net, twine or film is fed round the spinning bale, the rear tailgate swings up and the bale rolls out. For a well-shaped bale the row should be about as wide as the pickup, or the driver must weave to fill both ends of the chamber.

Main types

• Fixed chamber: The chamber is ringed with steel rollers and squeezes the bale from the outside in. Usually makes one size, around 1.2 m across, with a softer centre. Simple and strong, and widely preferred for wet silage.
• Variable chamber: Belts start small and expand as the bale grows, packing it from the centre out. The driver can choose the diameter, from about 0.6 m to 1.8 m on some models, and get a dense bale at any size. Often favoured for hay and straw.
• Baler-wrapper combination: A wrapper on the back covers each silage bale in plastic film as soon as it is made. Fast and saves a pass, but large and costly, so suited to contractors and big users.
• Small round baler: Compact machines for small tractors that make bales of roughly 50 cm across and about 20 to 25 kg.

Hooking it up to a tractor

A round baler hitches to the drawbar and is driven by the PTO shaft, which powers the pickup, rotor and chamber. Tractor hydraulics lift the pickup and open the tailgate, and an electrical lead feeds the cab monitor. Power needed depends on bale size, a chopper, hills and whether you are baling heavy silage, so check the maker's figures. Silage bales are heavy, so also check the tractor or loader that will handle them.

A short history

The idea dates to about 1910, but Allis-Chalmers' small Roto-Baler of 1947 was the first in real production, selling nearly 70,000 before 1960. Iowa State University built a large round baler in 1966, and in 1972 Vermeer began selling its belt-type 605, often called the first modern big round baler. By 1975 around fifteen North American firms were making them, and the round bale soon spread worldwide.

Buying and care tips

• Decide what you bale: A silage bale can weigh three to four times as much as a dry hay bale of the same size, so silage work needs a heavier machine.
• Net or twine: Net wraps faster and holds shape better than twine. Fixed chamber bales often need an extra layer of net to stop them swelling.
• Look at the pickup: More tine bars generally means a cleaner pickup and less leaf loss. Check for broken tines and worn cam tracks.
• Check chains, belts and rollers: Worn belts, roller bearings and drive chains are the costly items. Ask for the bale count and service history.
• Feeding out: Always remove net, twine and film before feeding, as animals can swallow it.

Questions people ask

What is the difference between a fixed and variable chamber round baler?

A fixed chamber uses rollers and makes one bale size with a softer core. A variable chamber uses expanding belts, makes a dense bale from the middle out and lets you choose the diameter.

How much does a round bale weigh?

A large round bale of dry hay or straw is commonly somewhere between about 500 and 1,000 kg depending on size and density. Wrapped silage bales are much heavier for their size.

Can a round baler make silage?

Yes. Grass is wilted, baled and then wrapped airtight in plastic film, where it ferments into silage. Fixed chamber balers are widely used for this.

Related equipment

Sources

1. Baler (Wikipedia)
2. Fixed or variable chamber: what's the best fit for a Kildare contractor? (Irish Farmers Journal)
3. Consider these factors when buying a round baler (Hay and Forage Grower)

Last checked 2026-11-01

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