The percentage of nitrogen in the atmosphere is 78 %. Nitrogen is very essential for living organisms as it is a constituent of proteins, vitamins, Chlorophylls, nucleic acids like D.N.A and R.N.A. The atmospheric nitrogen cannot be taken directly by plants and animals. Certain bacteria and Cynobacteria (blue green algae) fix the atmospheric nitrogen in the soil in form of nitrogenous compounds. In factories when chemical fertilizers are prepared and also during lightening, nitrogen is fixed in nitrogenous compounds.