The Nitrogen Cycle

Nitrogen in the atmosphere (N2) is the largest nitrogen reservoir on Earth.

Fixation converts atmospheric nitrogen (N2) into forms usable by organisms, such as ammonia (NH3).

The nitrogen cycle influences primary production and decomposition rates in ecosystems.

Denitrification completes the nitrogen cycle by reducing nitrates (NO3-) back into nitrogen gas (N2).

Under anaerobic conditions, denitrifying bacteria use nitrates for respiration, producing nitrogen gas (N2).

Anaerobic ammonia oxidation (anammox) converts nitrite and ammonia directly into molecular nitrogen gas.

Nitrogen fixation is the primary source of plant-available nitrogen in most ecosystems.

Nitrogen fixation converts nitrogen gas into nitrates and nitrites.

Nitrogen fixation primarily takes place in the soil.

Nitrifying bacteria convert nitrite into nitrate.

Conversion of ammonia into nitrates/nitrites prevents ammonia toxicity in plants.