High pressure increases the volume of spray delivered. A change in ground speed is the easiest way to obtain a small change in application rate. Faster ground speed decreases the volume applied per acre. Slower ground speed increases the volume. For a major change in the application rate, change the nozzle tip size.
Larger tips increase the volume, smaller tips decrease the volume.
This method also requires measuring and staking a test area of approximately 1000 feet for broadcast and 2000 feet for band application. Proceeded by putting water in the tank and note the level of the water. Put a sufficient amount to cover the test area. Tank should be level. Start the sprayer power unit and set the sprayer presssure.