I was going by memory and was thinking a quart per acre, glad to see spoon says the same rate. There used to be a big cotton field right across the fence to my Alfa Rack field and I never had any trouble with killing the cotton. The field is directly South though so predominant winds would tend to not push it in that direction. I've heard those wind drift horror stories. If you ever did kill somebodies cotton like that it could get expensive fast.