The Nitrogen Cycle

Nitrogen is an essential element for all forms of life, and is one of the main elements in amino acids, which make up proteins.
Nitrogen gas makes up about 78% of Earth’s atmosphere, but plants and animals cannot take it directly from the atmosphere.
The nitrogen cycle refers to the sequence of processes by which nitrogen, a key nutrient, moves through ecosystems.
The nitrogen cycle is composed of four main types of reactions: nitrogen fixation, ammonification, nitrification, and denitrification.
Nitrogen fixation is the process by which atmospheric nitrogen is converted into ammonia (NH3). This is carried out by bacteria such as Rhizobium in symbiotic relationships with legume plants.
Ammonification involves the conversion of organic nitrogen substances into ammonia. Decomposer microorganisms, such as bacteria and fungi, play an integral role in this stage.
During nitrification, ammonia is converted into nitrites (NO2-) and nitrates (NO3-) by bacteria. Nitrate is the form of nitrogen most accessible to plants.
In the denitrification process, nitrate is converted back into nitrogen gas by bacteria, returning it to the atmosphere and completing the cycle.
The nitrogen cycle is essential for maintaining the global balance of nitrogen. It ensures that nitrogen is continually recycled and available in forms that organisms can use.
Humans have a significant impact on the nitrogen cycle. Activities such as burning fossil fuels, using synthetic nitrogen fertilisers, and deforestation can disrupt the balance of the cycle.
Overuse of nitrate fertilisers can lead to eutrophication, a process where nutrient enrichment of water bodies leads to a rapid increase in algae, resulting in the depletion of oxygen levels and harm to aquatic life.
Understanding the nitrogen cycle is essential for sustainably managing and restoring ecosystems. It helps in predicting how changes in activities, like agriculture or industry, might influence ecosystems.