This past summer we hired a guy to sub soil four of our food plots that had been used as a log-set. These were very compacted red "Alabama" clay. It was a mess ! Looked like acres of red clay boulders !! He ripped about 8" - 10" or so deep using a HD 3 tine ripper and a 120 HP John Deere 4 wheel drive tractor. It was all this rig could manage.

Here's what I'd do. Find (if you can) a local farmer with similar HD sub-soiler set up and see if you can hire him rip the field. Probably a set-up with 2 or 3 rippers and a heavy 100+ HP. And probably in excess of $100/hr. That should get your place in plenty good shape. it will need to be harrowed back as smooth as practical for planting . A good working disc harrow or a PTO tiller type should do the trick.