[Ray 54]

Different chemicals for different problems need greater or lesser amounts of water. Every product label in the USA has a recomendad amount of water to use. Things like fungicides are a contact killer so you need the whole plant wetted. Things like Roundup that translocate thru out the plant not much water is needed. Most weed killers that translocate 5 to 20 gal per acre will work. In my locale because of permanente crops of trees and vines I am mandated to use a tip putting out 10 to 20 gal per acre, depending on my ground speed to reduce drift of fine particles.

Unless you only use one chemical every year you need to adjust you sprayer. To do a good job you need to check calibration of the sprayer more often than most of us want to.