Nitrogen is one of the most essential constituent of living beings. This is because nitrogen is part of chlorophyll, nucleic acids and vitamins. Plants and animals cannot directly consume the nitrogen present in the atmosphere. Animals get nitrogen from plants by eating them. Plants obtain nitrogen with aid of microorganisms. This is done by the blue green algae, i.e., cyanobacteria and bacteria present in soil. They fix the atmospheric nitrogen and convert it into nitrite and nitrate. The roots of the plants consume these nitrites and nitrates from the soil. The nitrogen is used to synthesise amino acid, proteins, etc. in the plants. This in turn is consumed by animals feeding on these plants. The dead bodies of these animals are worked upon by the bacteria and fungi present in soil. While decomposing their bodies, decomposers convert the compounds of nitrogen back into nitrates and nitrites. These compounds are further converted into nitrogen gas and released in atmosphere by certain specialised bacteria thus balancing the percentage of nitrogen in atmosphere. The complete process of nitrogen cycle is discussed in the given figure.
