Right now, all my 175 acres have something growing in them, except 1 acre that was in late broccoli.
Covers also aid in weed control to varying degrees.
But, you don't have to have a system like mine to receive these benefits. At the very least, try and get a cover planted for overwinter erosion protection. Think of how you can strategically place covers on your farm to enhance soil quality. My System A cover crop of hairy vetch and rye has proven most conducive to high vegetable yields at Cedar Meadow Farm, where tomatoes, pumpkins, and sweet corn are the top cash crops. I feel the components of the cover crop mix complement each other through different rooting actions and biomass production.