Wow zuzu, are you sure?
You may be thinking of Bell Beans, which are also V. fava, and a smaller end product.
Broad Windsor is much more productive, with a larger seed than what you will find in a cover crop mix. BW is the winter/cover crop I use on my corn field with the bonus of spring produce.
Favas won't work in our summer heat, the proper time for true beans.
Your whole county, really?
I'll post some prep info as we work through them.