Nitrogen is a crucial component of proteins and nucleic acids, the fundamental building blocks of all living things, and thus is essential to life on Earth. Gaseous N₂ from the atmosphere can be fixed by soil bacteria capable of converting N₂ to ammonia or nitrates (NO₃).

Nitrifying bacteria in the soil then convert ammonia into NO₃, which plants utilize for growth. Animals that consume plants put the N₂ back into the soil in the form of ammonia when they die or excrete waste.

The NO₃ in the soil is converted back into N₂ and released into the atmosphere by the activity of denitrifying microbes in the soil. This native nitrogen cycle regulates the N₂ levels in the atmosphere and on Earth and is vital for sustaining life.