Application Equipment, Calibration, and Recordkeeping
Equipment and nozzles
Sprayers must be matched to the job: flat-fan nozzles for broadcast herbicides, hollow-cone for directed or foliar insecticide/fungicide work, and air-induction tips for drift reduction. Pressure, orifice size, and speed set droplet size and output. Higher pressure makes finer droplets-better coverage but more drift. Worn nozzles increase output and distort pattern; replace them as a set. Keep screens, filters, and agitation working, and triple-rinse between products.
Calibration
Calibration answers one question: how many gallons per acre is this rig actually applying? Measure a course (often 100 ft), time it, convert to mph, measure nozzle output, then use GPA = (GPM per nozzle × 5,940) ÷ (nozzle spacing in inches × speed in mph). Calibrate with the carrier you will use and at the pressure you will run.
Records and stewardship
Records protect you and the crop. Typical entries: applicator name and credential number, date and time, site, target pest, product name and EPA registration number, rate and total amount, area treated, weather, and REI/PHI. Federal RUP records are kept at least 2 years; Michigan's commercial-applicator records have their own retention period, so verify the current MDA requirement. Records must be accurate and contemporaneous, not reconstructed later.
Traps
Calibrating only with water when the tank mix is thick; trusting the speedometer instead of a timed course; forgetting that nozzle spacing and boom height affect pattern; and recording a "planned" rate rather than the actual rate.
Worked example
A 100-foot course takes 20 seconds: 100 ÷ 20 = 5 ft/s; 5 × 0.6818 = 3.4 mph. If one nozzle collects 20 oz in 30 seconds, that is 40 oz/min = 0.3125 GPM. With 20-inch spacing at 3.4 mph: (0.3125 × 5,940) ÷ (20 × 3.4) = 1,856 ÷ 68 = 27.3 GPA.
Rule of thumb: calibrate, calculate, then check the tank-never guess GPA.