In article , FF
writes


I planted The Sutton again last weekend. I'm on acidic soil about an
hour away from where you are. The other thing about broad beans is to
leave the plants in as long as you can after you've eaten the beans -
cos they're good for the soil.

More specifically, nodules on the roots 'fix' loose nitrogen. When I
clear them, I usually break the tops off and leave the roots behind -
though thinking about it, this probably doesn't work as all the 'fixed'
nitrogen will have been passed to the leaves. But I compost them anyway,
so I still benefit.

It's part of the basis of crop rotation. Most plants can't fix nitrogen
in this way, so you plant the legumes (beans and peas) when the level of
nitrogen has been decreased by hungry crops, and plant a nitrogen liking
crop the following year.
--
Kay
"Do not insult the crocodile until you have crossed the river"