Nitrogen fixation is a process by which molecular nitrogen in the air is converted into ammonia or related nitrogenous compounds in soil. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Nitrogen fixation, any natural or industrial technique that reasons free nitrogen (N2), which is a exceedingly inert fuel considerable in air, to combine chemically with different elements to form extra-reactive nitrogen compounds including ammonia, nitrates, or nitrites.under ordinary conditions, nitrogen does not react with different elements. yet nitrogenous compounds are observed in all fertile soils, in all dwelling matters, in lots of foodstuffs, in coal, and in such certainly going on chemical substances as sodium nitrate (saltpetre) and ammonia. Nitrogen is also located within the nucleus of each dwelling cellular as one of the chemical additives of DNA.Nitrogen is fixed, or combined, in nature as nitric oxide via lightning and ultraviolet rays, however extra extensive quantities of nitrogen are fixed as ammonia, nitrites, and nitrates with the aid of soil microorganisms. more than ninety percentage of all nitrogen fixation is effected by way of them. two styles of nitrogen-solving microorganisms are diagnosed: unfastened-residing (nonsymbiotic) bacteria, such as the cyanobacteria (or blue-inexperienced algae) Anabaena and Nostoc and genera inclusive of Azotobacter, Beijerinckia, and Clostridium; and mutualistic (symbiotic) bacteria inclusive of Rhizobium, related to leguminous flora, and numerous Azospirillum species, related to cereal grasses.