Many here use variable rate fertilizing slaved to the yield mapping from the harvest operation. Most use GPS auto steer. I track rocks, weeds and photo points with a hand held GPS. Just mark a way point when going by and go back later to deal with it. Maps and inputs can be transferred to the office computer from the combine and airseeder with a memory stick. It is too expensive right now but the tools are there to track cow locations with GPS. (can't wait).
