You have treelines separating your fields, which I assume are fencerows. You can widen these travel corridors 2 different ways...by planting them with trees or by reducing the tilled area and letting them grow up naturally. The latter will require less expense, but it will take years for the natural regeneration to fill in the way you want it to do. Widening these areas to 50-75 yards should increase the number of deer utilizing your property significantly. If you plant trees, make sure they are adapted to your area...and preferably produce a beneficial mast for your deer/other wildlife.

I would leave the brushy areas of sumac alone forthe most partas they provide some very good cover where there is not much...you may consider brush-hogging ~15-foot-wide paths in those areas and seeding them to something likea clover/chicory mix...with those paths directing them to other places on your property where you have stands/food plots/cover.