Thanks - it would be in a 4 way mix so doesn't sound like it will add anything. (I actually think the hairy vetch variety we grow is also not adding enough and is usually swamped by the raddish.)It is incredibly slow to establish so won’t be a worthwhile size by the winter if sown in the autumn to benefit a cover crop.
i have a whole field of lucerne, planted in early september at the moment its welded to the floor, roots are probably 5-6 inches long. Its goes dormant in the winter so I cant see it being worth the cost of seed in a cover