Application Equipment and Calibration
Calibration questions test whether you can deliver the intended rate accurately and consistently. Know the basic relationship: application rate = output ÷ area covered, and that calibration must be checked before each significant job and whenever equipment changes. Understand nozzle types (flat fan, hollow cone, full cone, air induction) and their uses; droplet size and drift relationships; pressure effects on flow and pattern; and spray pattern overlap for boom sprayers.
Key concepts: nozzle wear (flow increases as nozzles wear, changing rate), nozzle spacing and height, boom height, speed effects, and agitation. For backpack and handheld equipment, know how to measure output over a known area. For aerial and ground rigs, know that calibration is a shared responsibility between operator and applicator.
Traps: Assuming a new nozzle matches the catalog rating (verify flow); confusing GPA (gallons per acre) with GPM (gallons per minute); ignoring speed changes that alter rate; and forgetting that worn nozzles over-apply. Also watch for questions about drift reduction - smaller droplets drift farther, and higher pressure creates more fines.
Rule of thumb: Calibrate with clean water before mixing product, and recheck after any nozzle, pressure, or speed change. If output is off by more than about 5–10%, investigate before spraying.
Worked example: A boom sprays 20 GPA at 4 mph. If the operator speeds up to 5 mph without changing pressure or nozzles, the rate drops proportionally (roughly 16 GPA), under-applying the field. Recalibrate or adjust pressure before spraying.