Image by Stephen Temple
By Heather Rhoades
Nitrogen for plants is vital to the success of a garden. Without sufficient nitrogen, plants will fail and will be unable to grow. Nitrogen is abundant in the world, but most of the nitrogen in the world is a gas and most plant cannot use nitrogen as a gas. Most plants must rely on the addition of nitrogen to the soil in order to be able to use it. There are a few plants that love nitrogen gas, though. They are able to draw the nitrogen gas from the air and store it in their roots. These are called nitrogen fixing plants.
How Do Plants Fix Nitrogen?
Nitrogen fixing plants do not pull nitrogen from the air on their own. They actually need help from a common bacteria called Rhizobium. The bacteria infects legume plants, such as peas and beans, and uses the plant to help it draw nitrogen from the air. The bacteria converts this nitrogen gas and then stores it in the roots of the plant.
When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to your garden.
How Nitrogen Nodules Raise Nitrogen in Soil
When legumes and other nitrogen fixing plants and the bacteria work together to store the nitrogen, they are creating a green warehouse in your garden. While they are growing, they release very little nitrogen into the soil, but when they are done growing and they die, their decomposition release the stored nitrogen and increases the total nitrogen in soil. Their death makes nitrogen for plants available later on.
How to Use Nitrogen Fixing Plants in Your Garden
Nitrogen for plants is essential to your garden but can be difficult to add without chemical assistance, which is not desirable for some gardeners. This is when nitrogen fixing plants are useful. Try planting a winter cover crop of legumes, such as clover or winter peas. In the spring, you can simply till under the plants into your garden beds.
As these plants decompose, they will raise total nitrogen in soil and will make available the nitrogen for plants that are unable to get nitrogen from the air.
Your garden will grow greener and more lush thanks to plants that fix nitrogen and their beneficial symbiotic relationship with bacteria.