The tractor as a power source
A farm tractor is less a tool than a source of power that can be attached to many tools. A diesel engine drives the wheels or tracks, but the engine also powers a hydraulic system and a rotating shaft at the back, so an implement can be pulled, pushed, lifted or driven. That versatility is why tractors are the basic machine on most farms, from small holdings to very large operations.
Sizes vary enormously, from compact tractors used on small plots and for property maintenance to large machines used on broad acreage. Which one makes sense depends on field size, crops, soil and the implements to be pulled, so it is better to start from the work than from the machine.
Four ways a tractor delivers power
Drawbar. The simplest connection is a pull. Plows, discs, cultivators and trailers are towed by a drawbar or hitch. Tractive effort, meaning the force available to pull, depends on weight, traction and tires as much as on engine power.
Three-point hitch. Most tractors have a standard three-point linkage at the rear. Its arms let the operator raise and lower an implement and hold it at a set depth, and they carry its weight so it does not rest on the ground. Many modern tractors adjust the hitch automatically in response to load.
Power take-off. The power take-off, or PTO, is a splined shaft at the back, and sometimes at the front, that turns at a standardized speed. A driveshaft connects it to an implement that needs rotating power, such as a mower, baler, rotary tiller, manure spreader or post-hole digger. The PTO delivers engine power directly and efficiently without needing hydraulic conversion, which is why it is so common. The shaft and its guards deserve respect: rotating driveshafts can catch clothing and cause severe injuries, so guards must remain in place and the machine should be shut down before anyone approaches the shaft.
Hydraulics. Remote hydraulic outlets supply pressurized oil to implements that need cylinders or motors, such as front loaders, folding frames and some planters. The general benefits of this approach are described in the article on hydraulic power advantages. Hoses and quick couplers on the back of a tractor are frequent wear points.
Under the skin
Tractors mix familiar components with some unusual ones. The transmission may be a set of gears with a clutch, a power-shift design that changes gear under load, or a continuously variable design. Final drives and differentials multiply torque at the wheels. Many tractors have gearbox lubrication needs that are demanding because the same oil can supply the hydraulics, brakes and transmission. Oils and intervals are set by the manufacturer, and they are worth following exactly.
Tires are a large part of performance. Large, low-pressure tires spread weight and improve traction while limiting soil compaction, and dual wheels or tracks serve the same purpose. Pressure is typically set for the task, with lower pressure in the field and higher on the road. Tire monitoring is covered in the article on tire pressure monitoring.
Implements and the jobs they cover
A rough calendar of field jobs shows where each type of implement fits:
- Tillage. Plows, discs, chisel plows and cultivators break up soil, bury residue and prepare a seedbed. Some farms reduce tillage to protect soil structure, using fewer passes.
- Planting. Planters and seed drills place seeds at a chosen depth and spacing. Many use ground-speed sensors and positioning to control seeding rates.
- Crop care. Sprayers apply fertilizer, herbicide and pesticide, and cultivators control weeds mechanically. Sprayers can be pulled behind a tractor or can be self-propelled machines. Chemical application is regulated and calls for trained, licensed operators in many places.
- Mowing and hay. Mowers, rakes and balers cut, gather and package forage.
- Hauling and handling. Trailers and grain carts move crops, and front loaders with buckets or forks move bulk materials. The wider topic is introduced in the article on agricultural handling equipment.
- Harvest. Harvesting is usually done by specialized machines instead of tractors alone, though tractors tow wagons, carts and some harvesters. The companion review of harvesting machinery covers those machines.
Chains, belts and bearings on implements
Much of an implement’s wear comes from its drivelines. Chain drives, belt drives and many greased bearings sit in dusty, wet and dirty conditions, so greasing and inspection schedules are key to dependable operation. A neglected bearing can stop a machine at harvest, which is the least convenient time for it.
Choosing a tractor
A few questions narrow the choices:
- What are the heaviest implements, and what do they need in power, hitch category and hydraulic flow?
- How much of the work is on slopes or in wet fields, which affects tires, tracks and weight?
- How many hours a year will it run?
- Does the farm need a front loader, a cab and air conditioning, or guidance support?
Used machines, rental and custom hire by neighbors or contractors are all realistic options, and compare costs over the life of the machine. The ideas in total cost of ownership apply to farm machines as they do to factory equipment.
Safety
Farm machinery causes serious accidents, many of them from rollovers, run-overs and rotating shafts. In general terms, safe use depends on rollover protection and seat belts where fitted, working within slope limits, keeping guards on, not carrying passengers on the tractor, shutting down before servicing and following the manufacturer’s manual and local rules. Operator training and good safe machinery operation habits are worth more than any one feature.