Carbon cycle

Nitrogen fixation

Atmospheric nitrogen is converted to form that produces can use. Biotic fixation, which produces ammonia, is carried out by cyanobacteria and some bacteria associated with plant roots. Abiotic fixation, which proceeds nitrates is carried about by lightning, combustion, and fertilizer production. 

Mineralization

Decomposes in soil and water break down biological nitrogen compounds into ammonium.

Nitrification

Nitrifying bacteria convert ammonium into nitrite and then into nitrate.

Denitrification

In the series of steps, denitrifying bacteria in oxygen-poor soil and statgant water convert nitrate into nitrite, nitrous oxide, and nitrogen gas.

Assimilation

Producers take up either ammonium, nitrite, or nitrate. Comsumers take up nitrogen by eating producers.