bobo there is no way you will keep deer in a 20 acre area unless you high fence it. What you need to do is provide them with reasons to at a minimum have them visit often. Food plots will help a lot, concentrate on plants that will be ready when the season kicks in. Another thing that will help is if one does not really exist is a bedding area, the thicker the better, it doesn't have to be big, just thick, if there isn't one then try creating one from native species as close to the center of your property as possible.