You may want to check into someone who has a stump grinder.You may have to dig up some of the roots that are close to the surface or you may catch your plow on them.If the area is accesible with a tractor or truck then you can be in luck the stump grinder can get them out in one day.I would probably keep one fo them larger ones to put some type of stump molassses or salt on them the deer will tear it up in the long run and the rotting stump is added fertilizer in the long run.