Crop sprayer

How it works

A pump, usually driven by the tractor's PTO, draws liquid from the tank through a filter and pushes it out to the boom. A regulator controls the pressure and sends any surplus back to the tank, which also keeps the mix stirred. The boom is split into sections, each with its own valve, so parts of it can be shut off at headlands and on ground already sprayed.

Nozzles are spaced evenly along the boom and break the liquid into a fan of droplets. The amount applied depends on nozzle size, pressure and forward speed, so a controller adjusts the flow as speed changes. The boom has to be held at the right height above the crop: too high and fine droplets drift away, too low and the spray pattern does not overlap properly. Booms fold for road travel, by hand on small machines and hydraulically on larger ones.

Main types

• Mounted sprayer: Carried on the three-point linkage with a tank of roughly 600 to 2,000 litres. Stable on slopes and handy in small fields.
• Front tank: An extra tank on the front linkage adds capacity to a mounted sprayer and balances the tractor.
• Trailed sprayer: Towed on the drawbar with tanks of about 2,400 to 6,000 litres and booms up to around 39 m. The axle carries the weight instead of the tractor.
• Self-propelled sprayer: A purpose-built machine with high clearance and even weight spread, built for big outputs on large farms and by contractors. Booms can exceed 50 m.

Hooking it up to a tractor

Mounted sprayers go on the three-point linkage and take PTO drive for the pump. Trailed sprayers hitch to the drawbar or a pick-up hitch, again with PTO drive, and use tractor hydraulics for boom folding, height and tilt. Both need power for the in-cab controller. Boom width should match your tramlines.

Testing and inspection

In the UK the National Sprayer Testing Scheme began in 2003 and works much like an MOT. In 2010 more than 14,200 sprayers were tested and over 62% needed repairs, most often for leaks and drips, worn nozzles and faulty pressure gauges. Testing is required by crop assurance schemes and, under rules that followed the EU Sustainable Use Directive, sprayers must be tested at set intervals. Check the current rules for your country before buying or using a sprayer.

Buying and care tips

• Ask for the test certificate: A recent pass shows the pump, gauges and nozzles were working properly.
• Replace worn nozzles: Nozzles wear and over-apply long before they look damaged. Check output against new nozzle figures.
• Look at the boom: Check for bent sections, worn hinges and loose wings. A boom that bounces will not spray evenly.
• Rinse after use: Clean the tank, pipes and filters after each job to stop residues damaging the next crop and corroding parts.

Questions people ask

Mounted or trailed sprayer?

Mounted sprayers suit smaller farms, small fields and hills. Trailed sprayers carry far more liquid and wider booms, cutting refill stops on bigger farms.

What is NSTS?

The National Sprayer Testing Scheme is the UK's sprayer test, similar to an MOT, checking for leaks, nozzle output, gauges and boom condition.

Why does boom height matter?

Nozzles are designed to overlap at a set height. Too high increases drift, and too low leaves stripes of under- and over-dosed crop.

Related equipment

Sources

1. Sprayers range (Kuhn UK)
2. Self-propelled versus trailed sprayers (Hardi)
3. National Sprayer Testing Scheme continues to grow (Farmers Weekly)

Last checked 2026-11-01

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