Nitrogen cycle

The nitrogen cycle is the process by which nitrogen is transformed between various chemical forms in the environment. Nitrogen is an essential element for all living things, but it is not readily available in pure form. Instead, it exists in the form of compounds such as ammonia, nitrates, and nitrites.

The nitrogen cycle begins with nitrogen fixation, a process by which certain bacteria and other microorganisms convert atmospheric nitrogen gas (N2) into ammonia (NH3) or ammonium (NH4+) that plants can use. This process can also be achieved artificially by the Haber-Bosch process used to produce artificial fertilizers. When nitrogen is in the form of ammonia or ammonium, it is taken up by plants and used to build proteins and other important molecules.Some bacteria also use ammonia as an energy source.

Then nitrification takes place. That is, ammonia or ammonium is converted to nitrite (NO2-) and then to nitrate (NO3-). This process is carried out by bacteria known as nitrifiers.

Nitrates produced by nitrification are taken up by plants and used for their growth and development. However, if nitrates are not absorbed by plants, they can be further converted to gaseous nitrogen through a process called denitrification. Denitrification is performed by bacteria living in anaerobic conditions (absence of oxygen), releasing nitrogen into the atmosphere.

Nitrogen cycling is an essential process for ecosystem health and essential for the production of food crops. However, human activities such as fertilizer use and fossil fuel burning can upset the natural balance of the nitrogen cycle and lead to environmental problems such as eutrophication (excessive accumulation of nutrients in water bodies) and air pollution.