Might be tough to get the ground-to-seed contact with a ton of residue top. But if it was only fallow for one season and it is covered with maretail (or few or little weed pressure), there might not be much on the ground. Now if it was covered in foxtail, it better be a heavy drill to cut through. Sure, we all would rather have the ground covered, but I think the success of the native grass seeding would out-weight the desire to leave the residue. I personally would try to disk or burn prior to drilling anything in a field that had been fallow, unless you can see dirt, but maybe they are keeping it mowed short. I am picturing the fallow field as a mess currently, it was an organic farm. They must be looking at a CRP program if it qualifies. Was it flooded or hailed out, too wet to plant this spring, why was it left fallow? Talk to the local PF habitat fellas and see what they recommend for a sucessful planting after they look at it. Good luck, hope it happens for you...and you get permission to hunt it!!