One reason I mix my plots, I call it the shotgun approach. Raps, Oats, Alfalfa, Winter Wheat, Rye and root plants, Radish/Beets. I plant plots in plots, a section of one thing, a section of another. I don't expect everything to do well, insects, weather and whatever is going to take it's toll, but I usually have something coming up always.
Alfalfa and Raps put down deep roots quick and seem to survive drought better. Root plants can go dormant for awhile and then continue growing. Cold hardy plants. like Raps and Oats survive some really low temperatures.
I try to have something going on all year round in my plots. Raps is really popular when it gets frosty out.