Neighbor approached me and has offered to sell her 20 acres immediately adjacent our place. Price is $75,000 which we will pay cash for, and can get about a 3% annual return from either crops or a CRP program of some type. It's not a big financial winner, but better return than I can get in a CD, plus assures long term that we will never have neighbors or development in that direction. Also increases size of our farm to 160 acres, which is a pretty big chunk for this neighborhood making the whole tract more valuable.
Most farmers will tell you that anytime you can buy adjacent land, you better do it, because that chance will probably only come around once in your lifetime.