If ground speed is doubled while nozzle pressure stays the same, what happens to spray per acre?

• A. Increase the gallons of spray applied per acre by 1/2.
• B. Reduce the gallons of spray applied per acre by 1/2.
• C. Increase the gallons of spray applied per acre by 2.
• D. Reduce the gallons of spray applied per acre by 2.

Answer: (A)

With a constant flow rate from the nozzle and the same swath width, the amount of spray applied per acre is inversely related to ground speed. If you double the ground speed, you cover twice as much ground in the same amount of time, so the same gallons are spread over a larger area, reducing gallons per acre by half. In other words, GPA_new = GPA_old × (old speed / new speed). Example: if you were applying 20 gallons per acre at 4 mph, at 8 mph you’d apply about 10 gallons per acre. To maintain the same GPA after increasing speed, you’d need to increase the flow rate by the same factor as the speed increase.