The process by which nitrogen and its compounds are converted into environment and in living organism through nitrogen fixation and decomposition.

Steps and Process of Nitrogen Cycle
1. Nitrogen Fixation
- Nitrogen gas (N2) is converted into ammonia (NH3) by nitrogen-fixing bacteria found in the soil or in the roots of leguminous plants.
- Some nitrogen-fixing bacteria are free-living, while others form symbiotic relationships with plants.
2. Nitrification
- Ammonia is converted into nitrites (NO2-) by nitrifying bacteria such as Nitrosomonas.
- Nitrites are further oxidized into nitrates (NO3-) by other nitrifying bacteria like Nitrobacter.
3. Assimilation
- Plants and other organisms take up nitrates and ammonia from the soil to use in their cellular processes, such as protein synthesis.
- Animals obtain nitrogen by consuming plants or other animals.
4. Ammonification
- Decomposers break down organic matter like dead plants and animal waste into ammonia through the process of ammonification.
5. Denitrification
- Denitrifying bacteria convert nitrates back into nitrogen gas, completing the nitrogen cycle.
- This process releases nitrogen back into the atmosphere, closing the loop.
This cycle is essential for the growth of plants, as nitrogen is a crucial component of amino acids, proteins, and nucleic acids. It also plays a significant role in the ecosystem by maintaining soil fertility and regulating the balance of nitrogen in the atmosphere.