Biological nitrogen fixation
Although N₂ is abundant in air, most plants cannot use it directly. Certain microorganisms convert atmospheric nitrogen into ammonia or related usable forms.

Microbes do the conversion
Nitrogen-fixing microbes use nitrogenase to reduce N₂ to ammonia. The reaction requires energy and the enzyme is sensitive to oxygen, so organisms have evolved ways to protect it and supply fuel.
Root partnerships
Some bacteria live in root nodules of legumes such as peas, beans, and clover. Other nitrogen fixers live freely in soil or water. Biological fixation complements lightning and industrial fixation; amounts vary by species and environment.
Sources and further reading
These references are starting points. Check the source directly for definitions, dates, units, and context. This is an educational overview, not an operating manual or professional advice.
Have a big idea for n2.si?
We expect a substantial offer; low bids will not be considered or answered. Answer two quick questions on the home page to open the English offer form.
A substantial offer should make even nitrogenase pause its shift and check the paperwork.