i’ve been using an injector with a tank to fertilize with the sprinkler. I have the pump wired to the pressure switch on the pump so it runs with the pump and i have a manual on off switch in line. When i fell the tank with fertilizer i flip the switch when ready and then either the tank runs dry or i turn the pump off manually. I could probably put a relay switch on another zone and use the OS to turn on and off the manual switch, but it would still be manual to activate the pump.