Lots will depend on the soils in that field road. My land is sandy.....so it works pretty easy. On my trails......after getting the timber off......I grind the stumps out. Then I pull my disc over it and drag it some until reasonably smooth for low speed travel. Oftentimes I till mine and then plant clover on it.
On non cultivated trails and on the gravel / dirt road in front of my place. I use my box blade to move dirt......and a landscape rake to grade the road (works better than a blade IMO).
My neighbor has quite a bit of traffic (he built the road years ago) and tears up the road pretty bad. We really need some class 5 and gravel on it....but we get along.
I JUST THIS MORNING saw a good old road grader for sale on Brainerd Craigs List. $500. Pulls with a ball hitch. Looks nice for road grading.
http://brainerd.craigslist.org/grd/4673350751.html