Nitrogen Fixing Root Nodules on Peas
It can be easy to take our soil for granted - we thoughtlessly walk on it, get it under our nails, and try to scrub it off at the end of each day. But the complexity of soil structure, the diversity of life and minerals found in the soil, and our reliance on the soil ecosystem to help grow our food and decompose our waste is awe-inspiring.
As we pulled our spent pea crops from our gardens this year, we saw a brilliant example of an important symbiotic relationship that takes place in the soil. Peas, beans, and other legumes have nitrogen fixing abilities. Or, more accurately, they have developed a relationship with a bacterium that can fix nitrogen.
Is Nitrogen broken? What does this mean?
Nitrogen fixation is the process of pulling atmospheric Nitrogen into the soil to make it accessible for plants.
So what does this have to do with peas?
Legumes and a handful of other plants have evolved complex symbiotic relationships with Rhizobium bacteria that live in the soil. The bacteria live in nodules on the roots of these plants. The plants send sugars down to the bacteria and the bacteria use the energy from these sugars to fix Nitrogen into the soil around their host plant.
As you can imagine, this is beneficial not only for the plant and the bacteria, but for the plants that inhabit the surrounding area.
It’s always a good idea to incorporate a Nitrogen fixing plant into your garden or landscape. Peas and beans are practical annuals for a vegetable garden. Clover or vetch are ground covers commonly used by farmers as nitrogen fixing cover crops. Black locust, Buckeyes, Alders, Bayberries, False Indigo, Senna, and American Elderberry are all native trees and shrubs said to have nitrogen fixing properties that could be incorporated into a backyard landscape.
Regardless of the plant you choose, take advantage of the fallen leaves or seasonal die-back - mixing this plant matter into your compost or soil to decompose is the best way to trap all of that new Nitrogen in the soil.