Editing Tractor (section)

=== Power take-off systems and hydraulics ===
In addition to towing an implement or supplying tractive power through the wheels, most tractors have a means to transfer power to another machine such as a [[baler]], [[swather]], or [[mower]].  Unless it functions solely by pulling it through or over the ground, a towed implement needs its own power source (such as a baler or combine with a separate engine) or else a means of transmitting power from the tractor to the mechanical operations of the equipment.

Early tractors used [[Belt (mechanical)|belts]] or cables wrapped around the [[flywheel]] or a separate belt pulley to power stationary equipment, such as a threshing machine, buzz saw, silage blower, or stationary baler. In most cases, it was impractical for the tractor and equipment to move with a flexible belt or cable between them, so this system required the tractor to remain in one location, with the work brought to the equipment, or the tractor to be relocated at each turn and the power set-up reapplied (as in cable-drawn plowing systems used in early steam tractor operations).

[[File:TractorPTOshaftMay04.jpg|left|thumb|An implement connected to a tractor's [[power take-off]] (PTO) shaft]]

Modern tractors use a [[power take-off]] (PTO) shaft to provide rotary power to machinery that may be stationary or pulled. The PTO shaft generally is at the rear of the tractor, and can be connected to an implement that is either towed by a drawbar or a three-point hitch.  This eliminates the need for a separate, implement-mounted power source, which is almost never seen in modern farm equipment. It is also optional to get a front PTO as well when buying a new tractor.

Virtually all modern tractors can also provide external [[hydraulic fluid]] and [[electric]]al power to the equipment they are towing, either by hoses or wires.