Broadbean nitrogen nodules: Costa replies to Kobie

Nov 4, 2020 | Gardening tips

Our member, Kobie Swart asked a question about nodules on the roots of her broadbeans on our Facebook page and received a detailed reply from Costa. (We are chuffed that Costa follows our page). Here’s Kobie’s question and photo (above) and Costa’s reply.

Kobie: Broadbean advice please!

I am just starting to pull up my broadbean plants (after my first ever harvest) and have noticed what I assume to be nematodes. Are they harmful to the plant? Should I keep them out of compost? Can I plant something (other than French marigolds) there this summer?

Costa’s reply

Those small white sacs are not nematodes they are actually known as nodules that form on roots of nitrogen fixing plants such as beans and are home for rhizobia. They are the house for a bacteria that works symbiotically exchanging carbohydrates from the plant for the bacteria and ammonium, from the bacterium, for the benefit of the plant.

It’s a place of serious deals under there. So you have the plant exchanging carbs to the fungi and the fungi making water and nutrients available for the plant. There is so much to learn about the soil food web but suffice to say these nodules are ok to go in the compost. Ahh soil. I love learning more about it each day. Not interested in going to mars and meteorites when we have planets and universes beneath our feet that are barely known and understood. And we all can be part of these small steps for humankind in our very own suburbs and backyards. 3,2,1 Houston, we are digg’n it. Costa.