broad bean roots and nitrogen fixing

[jayjaybee]

I know that legumes fix nitrogen in the soil. Now that my broad beans have finished I normally cut down the stalks and leave stumps and roots to semi rot. What I don't know is when this nitrogen fixing takes place. Do I really need to leave the roots to rot, or can I clear the ground now for replanting.

[Potstubsdustbins]

This used to be a common thought, though I understand there is now some controversy over whether it is actually true.

Potty

[zazen999]

It only works if the plant is cut down before podding up...I believe.

[rustylady]

Legumes fix nitrogen from the air for their own use. Once they have finished cropping you may as well pull the whole lot up and put on the compost heap.

[jayjaybee]

Many thanks guys. What a lot of time and land I have been wasting in the past. Broadbean roots...your days are numbered.
The vine and it's grapes come to the rescue once again.

[WilliamD]

Ditto. Was just about to start chopping up the roots I'd left in situ. That's one job saved

[Two_Sheds]

I know that legumes fix nitrogen in the soil.

Sort of.
They fix nitrogen on their roots for the benefit of themselves: it goes into pod production. Once the plant has podded, there's no nitrogen left on the roots.

"At the time of pod fill, nodules on annual legumes generally lose their ability to fix nitrogen, because the plant feeds the developing seed rather than the nodule"

NMSU: A-129: Nitrogen Fixation By Legumes