How do you calibrate a broadcast sprayer to apply the labeled rate per acre?

• A. Estimate by eye; adjust nozzles until area looks evenly covered.
• B. Determine output in gallons per minute, adjust pressure and nozzle pattern, and calculate gallons per acre based on speed and width to match the label rate.
• C. Use a standard factory setting regardless of speed.
• D. Only measure sprayer RPM.

Answer: (B)

Calibrating a broadcast sprayer to the labeled rate per acre hinges on tying how much liquid you’re actually applying to how much land you’re covering. Start by measuring the sprayer’s output in gallons per minute at the operating pressure you’ll use in the field. This gives you the actual flow rate, not just what the pump is capable of.

Next, ensure the spray pattern is uniform by adjusting the nozzle selection and spacing, as well as the system pressure, so every nozzle contributes evenly. A consistent pattern is essential so the calculated rate reflects the whole boom, not just a few good nozzles.

Then relate the flow to the area being sprayed. With a known speed and a known spray width (swath) you can determine how much area you cover per minute. Using the standard relationship between flow rate, speed, and width, you convert gallons per minute into gallons per acre. If the calculated gallons per acre doesn’t match the label, tweak the flow (via nozzles or pressure), adjust speed, or modify the swath width until the rate aligns with the label.

This approach is precise and compliant. Eyeballing coverage, relying on a factory setting without considering real operating speed or width, or using RPM alone doesn’t reliably achieve the labeled rate.