Application Equipment, Calibration, and Application Techniques
Equipment and droplet size
Know the major nozzle types and what they do: flat fan (tapered or even) for broadcast booms, hollow cone for directed or row-band work, full cone for coarse coverage, air-induction and drift-reduction tips for coarse, low-drift droplets. Droplet size drives both coverage and drift: smaller droplets give better coverage but drift farther. Higher pressure means smaller droplets and more drift; larger tips, lower pressure, and low-drift designs mean coarser spray. Flat-fan tips are normally spaced and height-adjusted to give 50% pattern overlap.
Calibration math
GPA = (GPM × 594) ÷ (MPH × nozzle spacing in inches). The 1/128-acre method is the field shortcut: for 20-inch nozzle spacing, drive 340 ft, catch each nozzle for the time of the run, and the average ounces caught equals gallons per acre. For other spacings, the course length is 4080 ÷ spacing (ft) or use a calibration chart. Nozzle flow varies with the square root of pressure - doubling pressure raises flow only about 41%, not 100%. Increasing ground speed lowers gallons per acre.
Handling and application
Follow the label's mixing order: fill the tank partway with water, add water conditioners, then dry formulations, then liquid formulations, then adjuvants and surfactants last, keeping agitation running. Triple-rinse or pressure-rinse containers. For chemigation, a functional check valve and vacuum relief are required to prevent backflow into the water source.
Worked example
20-inch nozzles, 340 ft course, average catch of 15 oz → 15 GPA. A 300-gallon tank covers 300 ÷ 15 = 20 acres. At a labeled 1 qt/A, add 20 qt. If you sped up to cut time, GPA drops and the rate goes under label - recalibrate instead of guessing.