Nitrogen is an important element for plant life. It comes only next to carbon. Hydrogen and oxygen as it figures into the composition of protein, nucleic acid, growth hormones and vitamins.
The plants though flooded with an atmosphere consisting of 78 percent nitrogen cannot absorb the elements directly from tl 2 atmosphere.
They depend for its supply on soil in which they grow. Some microorganisms are able to fix nitrogen. As a result they not only increase the production of inoculated crops but also leave a fair amount of nitrogen in the soil which eventually increases the fertility of the soil.
sThe uses of chemical fertiliser’s drasitically alter the nature of soil making it either too alkaline or too acidic. Also use of chemical fertilisers causes water pollution. Thus to restore fertility of the soil, it is advisable to grow a leguminous crop after each cereal crop as the leguminous plats fix nitrogen in the soil.