Mikein Ky you don't understand what you have bought. The PTO centrifugal pump is to agitate the spray solution while you are setting still. The ground drive pump meters the amount you want per acre within a speed range. So if you slow down or speed up the gallons per acre stays the same. The pressure and flow changes to match your ground speed. You have to go fast enough to make the nozzles work and slow enough that the flow does not max out. Usually a range between 3-10 MPH.
If you have a regular sprayer that you have to spray at a certain speed and pressure. You put more gallons per acre on when you slow down and fewer gallons per acre when you speed up.
The ground drive pump is a better system if it is working correctly. The PTO pump should just be for agitation only. Which is good as well because the spray solution will be kept mixed better. Some regular sprayer pumps do not have enough flow to agitate much when you are spraying.