170 acres of young pine should provide a good deal of cover. Personally, I would leave the hardwoods as they are (depending on what type of trees you are referring to - oak, hickory?), and focus on creating cover where the open hardwoods and fields/food plots meet. This is called edge feathering and can be accomplished in one of two ways - 1) use some of your field edge to plant a width of brushy vegetation, or 2) thin the existing trees at the edge of the woods and let succession run its course. Plantings in the first example could include wild plum, flowering/silky dogwood, Servicberry, Mulberry, Bicolor Lespedeza, etc. If you are determined to create some thick areas within your hardwoods, you may want to create some small clear cuts - they should grow back thick with excellent cover and browse.