A trailed sprayer is an agricultural machine pulled by a tractor to apply liquid products such as herbicides, fungicides, insecticides, or fertilizers across a crop field. It matters because accurate spraying protects crop yield while reducing chemical waste, fuel use, and environmental risk. The long boom spreads many nozzles over a wide working width, allowing a large area to be treated in each pass.
Understanding the machine helps operators connect farm practice with fluid mechanics, pressure control, and field efficiency.
Inside the sprayer, a pump moves liquid from the tank through filters, valves, hoses, and nozzles at a controlled pressure and flow rate. The application rate depends on nozzle flow, boom width, tractor speed, and the spacing between nozzles. Boom height and stability affect spray overlap, droplet placement, and drift, especially in wind or uneven terrain.
Modern trailed sprayers often use section control, rate controllers, GPS guidance, and agitation systems to improve uniform coverage and reduce skipped or double-sprayed areas.
Key Facts
- Application rate = total flow rate / field area rate
- Field area rate = speed × boom width
- Nozzle flow rate usually increases with pressure as Q2 = Q1 × sqrt(P2 / P1)
- For equal nozzle spacing, nozzle flow = application rate × speed × nozzle spacing / 600 when using L/min, L/ha, km/h, and m
- Spray drift increases when droplets are too small, wind speed is high, or boom height is too large
- Tank capacity, boom width, and travel speed determine how often the sprayer must stop to refill
Vocabulary
- Trailed sprayer
- A wheeled sprayer pulled behind a tractor that carries a tank, pump, boom, and nozzles for applying liquid products to fields.
- Boom
- The long folding frame that holds spray nozzles at regular spacing across the working width of the machine.
- Nozzle
- A small outlet that controls the spray pattern, droplet size, and flow rate of liquid leaving the sprayer.
- Application rate
- The volume of spray mixture applied per unit land area, commonly measured in liters per hectare.
- Spray drift
- The movement of spray droplets away from the target area due to wind, droplet size, boom height, or air turbulence.
Common Mistakes to Avoid
- Using pressure alone to set the application rate is wrong because travel speed, nozzle size, and boom width also control how much liquid reaches each hectare.
- Raising the boom too high is wrong because it increases droplet travel distance, uneven overlap, and the chance of spray drift.
- Ignoring clogged or worn nozzles is wrong because one bad nozzle can underapply or overapply a strip of the field even when the tank pressure looks correct.
- Driving faster without recalibrating is wrong because the same nozzle flow is spread over more area, which lowers the application rate.
Practice Questions
- 1 A sprayer has a 24 m boom and travels at 8 km/h. What is its field area rate in hectares per hour?
- 2 A sprayer needs to apply 150 L/ha at 10 km/h with nozzles spaced 0.50 m apart. What flow rate should each nozzle deliver in L/min?
- 3 Explain why a sprayer operator might choose larger droplets and a lower boom height on a breezy day, even if smaller droplets can improve leaf coverage.