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Nitrogen-Fixing Bacteria - For Your Peas, Beans And Other Legumes

EM

Most of us have heard the expression, "nature, red in tooth and claw."

When Tennyson wrote this line back in 1850, he was saying that nature is competition, a struggle to eat or be eaten.

But what if nature has a different story to tell?

While it’s true that competition is one of the driving forces of the natural world, it’s equally true that cooperation is the fundamental basis of life on earth. Here’s how:

Plants form the base of the food chain on land, algae in the sea. The role of plants is to be eaten.

This is because of a really important thing that plants and algae can do, that animals can’t – they capture energy from the sun through the process of photosynthesis, and bring it into themselves.

But did you know that in order to perform this essential function, plants are completely dependent on partnership with another set of organisms?

In order to photosynthesize, reproduce, and even just to live, plants must create amino acids, proteins, and enzymes that incorporate nitrogen in their basic structure.

At first glance, this shouldn’t be a problem, since we’re conveniently surrounded by nitrogen gas all the time. In fact, the air is mostly made of it, at 78% nitrogen by volume.

But there’s a catch.

Unfortunately, even though we, and plants, are swimming in all of that lovely, protein-building nitrogen all the time, we can’t get it!

In fact, without the help of bacteria, life wouldn’t be possible at all, because only bacteria can get hold of that nitrogen.

Nitrogen-Fixing Bacteria To The Rescue

This is what we mean when we say all life depends on the fundamental cooperation between carbon fixers and nitrogen fixers.

Not all bacteria are nitrogen fixers. In fact, it turns out that among the small percentage of bacteria that do fix nitrogen, it really matters which ones are around which plants.

Plants have preferred associations with particular types of nitrogen-fixing bacteria, most of them from the group Rhizobia.

For gardeners, where this really matters is with the plants that are often labeled as "nitrogen fixers."

Most of these plants are from the legume family, including all peas and beans, though a few important ones such as alders and ceanothus are from other families.

In reality, these plants don’t fix nitrogen themselves, because plants can’t do that. What happens is that these particular plants form associations with specific strains of nitrogen fixing bacteria, often making homes for the bacteria right inside their own roots.

These “nitrogen fixing plants” are really great hosts.

In fact, they’re so keen on hooking up with their preferred Rhizobium bacteria that their root hairs search the soil for the right species, then encircle the bacteria colony and create a nodule about as big as a kernel of corn so the bacteria can live inside their roots.

Then they feed the bacteria carbohydrates and other organic substances they need to live. In exchange, the bacteria convert nitrogen from the air into ammonia which the plants use to build amino acids.
Unfortunately, these bacteria may not be numerous enough to provide optimum nitrogen fixation when that next legume is planted. That’s where we come in.

To make sure our leguminous plants have an ample supply of the right nitrogen fixing bacteria to get a great start on growth, we can supply these bacteria in the form of inoculants.

This is way better than supplying synthetic nitrogen, because instead of interfering in a heavy-handed way that can have unintended consequences, we’re essentially supporting the living organisms to work in community, in the way that nature intended them to do.

It seems most nitrogen-fixing partnerships contribute more usable nitrogen to the soil than they need for themselves, especially after they die but often even when they’re alive. This is why legumes and nitrogen fixing pioneer plants like alder and clover are thought of as "soil builders."

So you can see that the myth of nature as a place of violence and competition is really just a small part of the story. What’s absolutely fundamental and indispensable in nature is partnership and cooperation.

By supporting this partnership, we change our role as gardeners from one where we strive for total control – and in the process disrupt the natural cooperation within the soil ecosystem and make a lot of work for ourselves – to one of creative relationship managers, enhancing and supporting the partnership of life.

So if you're planning to plant any peas, beans, clover, vetch or any other legumes any time soon, you might want to check out this nitrogen-fixing bacteria in more detail.