Why Do Plants & Animals Need Nitrogen?

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

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.

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.

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

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.