Sounds about right, just follow the label. I can't imagine you would need 50 gallons of spray solution. As for using soap, I would not suggest you doing that. A wetting agent helps spread the spray over the leaf surface as well as penetrate the plant cuticle. Not sure is soap will help spread the spray.

Brad Vollmar
Vollmar Pond and Lake Management
www.texaspondmanagement.com

____________________________________
What's the difference between a lake and a pond?
If you are selling it's lake!
If you are buying it's a pond!