[Edd in KY]

Isn't the real question is how much water is needed to spread the chemical so that every plant is wetted by the solution?
My experience is that 10 gal is a little short....15 is a bit more reliable, and 20 is pretty sure. But 20 means more refill trips, depending on sprayer tank size and field size. I dislike the job of spraying, so I try to do it in a way that one trip gets the job done for the year.