Application Equipment, Calibration, and Application Techniques
Matching equipment to the job
Application equipment must deliver the right rate uniformly to the target. Know the common types: hydraulic boom sprayers with flat-fan, even-flat-fan, hollow-cone, and air-induction nozzles; boomless and boom-buster setups; backpack and hand sprayers; air-blast sprayers; granular spreaders; and injection or chemigation systems. Nozzle selection sets droplet size, which drives drift and coverage: fine droplets give better coverage but drift more; coarse droplets reduce drift but can run off the leaf.
Pressure, speed, and droplet size
A frequent exam trap: raising pressure increases flow and produces finer droplets, worsening drift. Increasing speed reduces gallons per acre. Changing nozzle tips is the correct way to make large rate changes; small changes can be made with pressure or speed only within limits.
Calibration
Calibrate at the start of the season, whenever you change nozzles, products, or speed, and periodically during the season. The standard boom formula:
GPM per nozzle = (GPA × MPH × nozzle spacing in inches) ÷ 5940
Worked example: you want 20 GPA at 5 mph with 20-inch nozzle spacing. GPM = (20 × 5 × 20) ÷ 5940 = 2000 ÷ 5940 = 0.34 GPM per nozzle. Select a tip that delivers 0.34 GPM at your chosen pressure. Also check the pattern with a spray table or catch cans - replace worn tips, which over-apply and skew the pattern.
Tank mixing and technique
Follow the label's mixing order (typically: fill partly with water, add compatibility agents, then dry formulations, then liquids, then surfactants last). Keep agitation running. Verify compatibility with a jar test when unsure. Set boom height to give correct overlap (typically 50% for flat fans), match speed to the gear used during calibration, and watch wind, temperature, and humidity to avoid drift.
Rule of thumb
"Calibrate, then calculate, then check" - never trust a sprayer you have not measured this season.