1. Nitrogen Fixation:

Atmospheric nitrogen gas (N2) is converted into ammonia (NH3) by certain microorganisms, such as bacteria and archaea. This process occurs in the soil or through industrial processes.

2. Nitrification:

Ammonia is oxidized by nitrifying bacteria into nitrite (NO2-) and then into nitrate (NO3-). This occurs in aerobic conditions in the soil.

3. Assimilation:

Plants absorb nitrate and ammonium from the soil through their roots and use them to synthesize essential nitrogenous compounds like amino acids, proteins, and nucleic acids.

4. Ammonification:

When plants and animals die, their nitrogen-containing compounds are broken down by decomposers (bacteria and fungi) through a process called ammonification. This releases ammonium (NH4+) into the soil.

5. Nitrification:

The ammonium released during ammonification is further oxidized by nitrifying bacteria into nitrite (NO2-) and nitrate (NO3-).

6. Denitrification:

Under anaerobic conditions (absence of oxygen), certain bacteria convert nitrates into nitrogen gas (N2). This process is known as denitrification and releases nitrogen back into the atmosphere.

7. Biological Nitrogen Fixation:

Some bacteria and archaea have the ability to fix atmospheric nitrogen directly into ammonia. This process is crucial in enriching the nitrogen content of the soil and supporting plant growth.

These steps are interconnected, and the nitrogen cycle is a continuous process that ensures the availability of nitrogen in various forms for living organisms.