In article , Pam Moore
writes
I THINK I've heard that rotation doesn't matter so much with beans as
they fix their own nitrogen.
But if you cut off the broad bean stems and leave roots in the ground
you will have the benefit of the nitrogen nodules on the roots for
whatever you plant next.

That's right, peas, beans and all other legumes leave nitrogen in the
ground which can be used by a following crop. That doesn't affect the
need for crop rotation though. Repeated growing of the same plant family
will result in a build up of diseases regardless of how much nitrogen is
in the soil.
--
Alan & Joan Gould - North Lincs.