I use my 25 gallon 12 volt sprayer for herbicides both on the yard and the pasture. It's trailer mounted and has a 5' boom that sprays about an 8' pattern. It's really better suited to the yard than the pasture. I have a 55 gallon 3-pt mounted, PTO driven sprayer that I use for insecticides and very, very occasionally herbicides in the wide open parts of the pasture. It has a a single post broadcast spray. What size you get depends on how much you have to spray. Even with the 25 gallon tank, I have to refill it about 4 times to cover the whole yard. If you are going to use it to spray herbicides, get a boom on it. You'd be surprised how far the spray can drift even with just a light breeze. Don't ask me how I know. /forums/images/graemlins/smirk.gif