Nitrogen cycle

• Our atmosphere has 78% nitrogen gas.
• Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins.
• The atmospheric nitrogen cannot be taken directly by plants and animals.
• Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Such conversion is known as nitrogen fixation.
• Once nitrogen is converted into these usable compounds, it can be utilized by plants from the soil through their root system.
• Nitrogen is then used for the synthesis of plant proteins and other compounds.
• Animals feeding on plants get these proteins and other nitrogen compounds. This process of utilizing absorbed nitrogen for synthetic purposes is known as assimilation.
• When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again and the process is known as nitrification.

• Certain other bacteria convert some part of them to nitrogen gas which goes back into the atmosphere and process is known as denitrification.
• As a result, the percentage of nitrogen in the atmosphere remains more or less constant.

Nitrogen Cycle:

Representative diagram of Nitrogen Cycle: