Why Do Plants & Animals Need Nitrogen?

••• Sujinphoto_iS/iStock/Getty Images

Nitrogen is a building-block element both in the atmosphere, where it is the most abundant gas, and in organisms. Its flow through earth’s atmospheric, geological and biological systems—the nitrogen cycle—is one of ecology’s grand choreographies.

Nitrogen's Biological Role

Nitrogen is required by plants and animals for production of proteins and amino acids.
••• Digital Vision./Digital Vision/Getty Images

Nitrogen, fundamental for cellular structure, is required by plants and animals for production of proteins and amino acids.


One of the components of chlorophyll is nitrogen.
••• TongRo Images/TongRo Images/Getty Images

One of the components of chlorophyll, the plant pigment that facilitates photosynthesis, is nitrogen. It plays a role in this immensely important transformation of solar energy.


Usable nitrogen is a limited commodity.
••• Margaryta Vakhterova/iStock/Getty Images

Although 78 percent of our atmosphere is comprised of nitrogen gas, usable nitrogen is a limited commodity. Most organisms can tap the element for growth and function only when, through a process called nitrogen fixation, it has been converted into ammonia or nitrates.

Nitrogen Fixation

Fixation is accomplished by bacteria in soil.
••• Geo-grafika/iStock/Getty Images

Fixation accomplished by bacteria in soil—often in symbiotic relationship with fungi and plants—provides the bulk of nitrogen available to the biotic community.

Nitrogen Cycle

Lightning passes nitrogen gas through the atmosphere.
••• Ivan Archipov/iStock/Getty Images

This gas passes through the atmosphere, rocks, lightning, plants and animals, facilitating growth and being liberated by organic waste and decay in a fundamental biogeochemical cycle.


About the Author

Ethan Shaw is an independent naturalist and freelance outdoors/nature writer based in Oregon. He holds a B.S. in Wildlife Ecology and a graduate certificate in G.I.S. from the University of Wisconsin-Madison. His primary interests from both a fieldwork and writing perspective include landscape ecology, geomorphology, the classification of ecosystems, biogeography, wildlife/habitat relationships, and historical ecology. He’s written for a variety of outlets, including Earth Touch News, RootsRated, Backpacker, Terrain.org, and Atlas Obscura, and is presently working on a field guide.

Photo Credits

  • Sujinphoto_iS/iStock/Getty Images