Nitrogen is the most abundant element in the air around us and a vital component in plant growth. It is a major component in plant growth as part of chlorophyll (to produce energy and sugar through photosynthesis), a major component of amino acids (the building blocks of proteins), and a component of nucleic acids found in DNA. In short, without nitrogen, there wouldn’t be life as we know it on Earth!

Nitrogen is the main component in the air around us and accounts for 78% of dry air. Despite this abundance, the nitrogen in the air (N2) around us is not easy accessible by plants. It must be “fixed” or transformed into a more accessible substance before the plants can take it up. This process involves a series of chemical changes, typically by bacteria or algae in the soil or water that combines nitrogen with other elements to form useful and more active compounds. For this reason, adding nitrogen rich fertilizers or planting nitrogen fixing plants are two common ways to provide this essential element to your plants.

In vegetable gardens, the most common nitrogen fixers are found in the legume family and include plants like peas, beans, alfalfa, and clover. Working in a symbiotic nature with a common bacteria called rhizobium, these plants take nitrogen out of the air and store it in nodules along their roots. This is why you may have seen some of these seeds sold with an innoculant powder already applied or a note suggesting you to coat the seeds with this bacteria (available in an easy to apply powder) to ensure healthy plant growth and nitrogen fixing as they grow. When the plant dies, decomposition then releases the nitrogen into the soil for other plants.

Farmers and growers take advantage of this natural process by planting nitrogen fixing crops as part of their rotation schedule. Once the plants reach maturity, or before the next crop is sown, these nitrogen fixers (also called green manures) are then chopped up and plowed under the soil to provide nutrients and nitrogen to the soil.

Outside of the legume family, here are also other a few native trees and shrubs that can fix nitrogen as well. Common plants in Ontario include Black Alder (Alnus glutinosa), Western Red Alder (Alnus rubra), Russian olive (Eleagnus angustifolia), and Scotch broom (Cytisus scoparius).

Too little nitrogen is often seen with yellowing leaves, while too much nitrogen typically causes lush leafy growth at the expense of flowers/fruits/roots. If your garden is lacking nitrogen, consider incorporating green manures and other nitrogen fixing plants into your crop rotation plan. Or talk to us about how we can help you plan and get the most out of your garden with our coaching and planning, and maintenance services.

Cover Image by free photos, used under its Creative Commons license.

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