What are the three controlling factors for a uniform backpack spray on a percentage basis?

• A. Nozzle size, the pressure used, and the time the nozzle is on the target area.
• B. Tank size, truck speed, and wind speed.
• C. Pesticide label color, water temperature, and nozzle cap type.
• D. Operator experience, field size, and humidity.

Answer: (A)

When aiming for uniform spray coverage by percentage, the amount of chemical delivered per unit area is controlled by three practical settings you adjust on the backpack sprayer. First, the nozzle size determines how much liquid flows each second and the droplet size produced; a smaller nozzle uses less liquid and makes finer droplets, while a larger nozzle increases flow and often yields coarser droplets. Second, the pressure used affects the rate at which liquid exits the nozzle and also influences droplet size distribution; higher pressure can raise the flow rate and shift droplet sizes, which changes coverage and potential drift. Third, how long the nozzle is on the target area—the spray on-time or duration—sets the total amount applied to that spot; keeping all other factors constant, longer on-time increases the percentage of the area that receives spray.

Other factors like tank size or wind speed relate to capacity and drift or application conditions, but they don’t directly determine the per-area percentage of coverage in the same controlled way as nozzle size, pressure, and on-time.