If the throttle setting remains constant and speed doubles, how does the amount of spray per acre change?

When the throttle setting of a spray application system remains constant, it means that the output rate of the nozzle is fixed. If the speed of the application double, the distance covered in a given timeframe also doubles. Since the amount of product being sprayed is defined by the output rate from the nozzle and the speed of travel, doubling the speed effectively means that the same volume of spray is applied over twice the area in the same amount of time.

As a result, while the total amount of spray being applied does not change, the amount of spray per acre decreases because that same volume is now being distributed over a larger area. Thus, the spray per unit area (acre) is halved when the speed doubles, leading to a reduction in the concentration of spray that each acre receives.