I'm in northwest Iowa and would like to try applying a cover crop in my standing corn. The purpose of this cover crop would be to apply radishes for soil compaction as well as some form of cover to allow fall and winter grazing for my stock cows. I have an airplane lined up and they charge a flat fee plus a fee for pounds per acre applied. What are by best choices for a cover crop laying above ground that will germinate and grow.  understand that timely rains are key to the success. I would still like suggestions on which crops would work best in this situation (rye, oats,wheat) ?