I don't know how much timber you have to hunt along your ag fields but I like to find the travel routes and set up where the bucks will stage before they head to feed. This could be pretty far off the field edge but it is a great ambush spot. Try to put up trail cameras to pin point these areas.
Also if you must hunt field edges try to find the corners of the fields where two sections of timber form an L shape or curve. Another thing to look at is the crop harvest here in Central IL harvest probably won't start until the last week of Sept. and harvet is usually 8-10 weeks. So you may have to adjust your plans according to when your land is harvested.