Application Methods, Calibration, and Drift Management
Application Methods, Calibration, and Drift Management
This domain tests matching the method to the site, calibrating output, and preventing off-target movement.
Core rules
- Methods include broadcast, band, spot, directed, basal, soil injection, chemigation, and aerial; choose based on label, site, pest, and drift risk.
- Calibration determines actual output. For boom sprayers: GPA = (GPM × 5940) ÷ (MPH × nozzle spacing in inches).
- Check speed, pressure, nozzle spacing, and swath; recalibrate after nozzle changes.
- Drift is influenced by droplet size, boom height, wind, temperature inversions, humidity, and adjuvants.
- Use low-drift nozzles, lower pressure, shielded booms, buffer zones, and label wind restrictions.
- Avoid spraying during inversions, near sensitive sites, or when bees are foraging.
Worked example
A nozzle outputs 0.4 GPM at 4 mph with 20-inch spacing. GPA = (0.4 × 5940) ÷ (4 × 20) = 2376 ÷ 80 = 29.7 GPA. Reasoning: if the label requires 30 GPA, this is close; adjust pressure slightly or accept within calibration tolerance, then verify by measuring output from several nozzles. If one nozzle is 0.5 GPM, replace it before spraying.
Traps
- Calibrating only one nozzle.
- Using pressure to fix a worn nozzle.
- Spraying in a temperature inversion because the surface is calm.
- Ignoring buffer zones on the label.
- Assuming a drift-control adjuvant replaces correct nozzles.