I've never cut any soybeans for hay, although they do make good hay. There are varieties that are grown specifically for hay, I do know that. If you cut them for hay, you might get some regrowth, but it would not be anywhere near enough for a second cutting. I've seen places in a beanfield where the groundhogs or rabbits had eat the young beans down to the ground, and after they were killed, the beans would grow back out. But, that's not like mowing them down for hay after they are fully grown.
I've also seen people bale the bean straw after the beans were combined. We did it after the first crop of soybeans I ever grew. Made some decent hay.
