Can You Briefly Describe Nitrogen Cycle?

: "The circulation of free nitrogen from the atmosphere to protein through plants and animals and finally back to atmospheric nitrogen is called nitrogen cycle."
      The nitrogen cycle consists of a series of reactions of nitrogen and its compounds. Almost all of these reactions take place through living organisms such as green plants and bacteria.
Process by which atmospheric nitrogen is consumed :-

1)As a result of electric discharges in the atmosphere , the nitrogen and oxygen present in the atmosphere combine to form nitric oxide. NO which further combines with oxygen to form nitrogen dioxide,NO2. The oxides combine with water to form nitrous acid HNO2 and nitric acid HNO3.  These acids are carried down to soil by rain. These oxyacids combine with the lime present in soil to form nitrites and nitrates which are used up by the plants.

2) Symbiotic bacterias which live on the nodules of leguminous plants such as peas, beans or gram , etc: directly take up atmospheric nitrogen producing nitrogenous compounds such as ammonia and nitrates. These soluble compounds of nitrogen are absorbed by the roots and thus converted into proteins. Plant protein is converted to animal protein through feeding by animals and human beings. In the animal body the protein is converted into simpler compounds like urea and amino acids.
As result of these processes, a very large quantity of nitrogen is taken away from the atmosphere.

Processes by which nitrogen is released in the atmosphere:
The decay of plant and animal proteins leads to the formation of ammonia. Ammonia is then converted into nitrates and nutrifying bacteria. These nitrates are then decomposed into free nitrogen by denitrifying bacteria. The free nitrogen mixes in the air.