With permission from the NRCS you can do mid contract renovation on CRP acres.
I did a project for a friend where we converted existing bromegrass cover to tallgrass prairie,shrub planting and a combination of partridge pea,illinois bundleflower and clover. The existing brome had virtually no wildlife value since it was nearly a 100% brome monoculture that averaged 12" in height. The brome was mowed, allowed to regrow to about 5-8" and sprayed with Roundup. The areas where the shrubs and legumes were to be planted were disked lightly. The legumes were seeded using a cyclone spreader as a fall frost seeding. The prairie grass was seeded using a no till Truax drill at the same time as the legumes. The owner received a combination of cost share money from the local Pheasants Forever chapter, USFW and the REAP program. The results after one year of growth: (1)This year will tell more about the prairie grass (2) About 95% of shrubs are alive (3)The legume areas have a wide diversity of species both planted and volunteer and probably averaged 3' in height.
When mowing, spraying,disking and planting the area I saw one lone quail and found one small 3 point shed. While checking the area this winter after one year of growth I jumped a covey of 25-30 quail and later found 4 new sheds in the planted areas. I know this is anecdotal evidence but it is very encouraging. The biggest thing I learned in this project was that we could have achieved a large portion of the benefits from simply spraying and disking the legume areas and allowing the seed bank in the soil to repopulate the areas. Clovers were very prolific even in areas where they were not seeded even though they were vitually non-existant in the brome grass. The only real failure seemed to be the lack of Illinois bundleflower in the new seeding.