Jeff Frey at Future View Farm, farms 700 acres of cash grain, corn, soybeans, wheat and barley, and finishes hogs. He typically plants directly into the cover crop before terminating it, which provides better mulch by letting the cover crop grow longer.
He would like to broaden his use of cover crops, but for now his main species is wheat, which has the primary benefit of slowing erosion. In his view, 30 years of no-till has made his soil more fragile, so the wheat cover crop's root mass helps hold the soil in place.
The second benefit is the nutrient recycling from the hog manure he puts down.