What are the steps of the nitrogen cycle

The natural nitrogen cycle simply explained (chemistry)

The natural nitrogen cycle, also known as the nitrogen cycle, describes the migration and conversion of nitrogen on earth.

Nitrogen is contained in every living organism, be it bacteria, plants, fungi or animals, as it is an important building material in proteins, amino acids and DNA. Since the cells have to be renewed regularly, they have to be supplied with the necessary substances such as nitrogen again.

The natural nitrogen cycle:

  1. Ammonification
  2. Nitrification
  3. Nitrogen assimilation
  4. Denitrification
  5. Nitrogen fixation
  6. Nitrification by energy

1. The ammonification

The nitrogen cycle "starts" with the ammonification. During this process, the nitrogen, which is contained in all compounds in organic substances, is released by destructors such as bacteria and fungi. These destructors decompose the organic parts and thus generate energy. Ammonification can not only take place through destructors, but also through other chemical processes such as the hydrolysis of urine.

Ammonification makes nitrogen available to the ecosystem again in the form of NH3 or NH4 +.

2. Nitrification

Nitrification takes place in a two-step process consisting of two groups of bacteria, the nitrite bacteria and the nitrate bacteria. The two groups of bacteria work interdependently, as ammonia first has to be converted into nitrite and then into nitrate.

The first step is carried out by the nitrite bacteria. These oxidize ammonia with molecular oxygen to nitrite in order to gain energy from this process.

NH3 + 1.5 O2 → NO2- + H2O

Nitrate bacteria such as Nitrobacter are necessary for the next step, since nitrite is converted into nitrate through oxidation.

NO2- + 0.5 O2 → NO3-

3. Nitrogen assimilation

Nitrate and ammonia are inorganic compounds and are absorbed by plants and other organisms to form nitrogen-containing organic compounds such as amino and nucleic acids or proteins.

Both ammonia and nitrate have a fertilizing effect on plants and stimulate growth.

Many plants store more nitrate than they need, which is why it can be a health hazard to reheat highly nitrate-storing vegetables such as Swiss chard or spinach more than once. Artificial nitrification through heat, e.g. in a saucepan, produces nitrite, which can be toxic, especially for children.

The excretions and remains of microorganisms, plants, fungi and animals also contain nitrogen. This is either converted to ammonia by ammonification or released by other chemical processes.

4. Denitrification

Various anaerobic bacteria can use nitrate or nitrite for oxidation and thus gain energy for themselves. In several intermediate steps, nitrate or nitrite N2 is produced, most of which escapes into the atmosphere.

5. Nitrogen fixation

Very few living things are able to bind nitrogen in its original form and thus make it accessible to plants and microorganisms. The rare species include cyanobacteria, bacteria of the genus Frankia and various other bacteria such as the nodule bacteria.

These mostly live in symbiosis with plants, where they benefit from the exchange of substances.

6. Nitrification by energy

Nitrogen found in the atmosphere is bound to nitrate during a thunderstorm.

Loading ...