Nitrogen fixation

Reduction of atmospheric nitrogen (N₂) to ammonia.

Although atmospheric nitrogen is available in large amounts, many organisms are not supplied sufficiently with this nutrient. They only can take up nitrogen in the form of nitrate or ammonia from the soil. A number of bacteria, however, is able to reduce atmospheric nitrogen to ammonia (fixation). In some cases, such bacteria are forming symbioses with plants (e.g. forming root nodules).