Nitrogen-fixation

noun
1.
any process of combining atmospheric nitrogen with other elements, either by chemical means or by bacterial action: used chiefly in the preparation of fertilizers, industrial products, etc.
2.
this process as performed by certain bacteria found in the nodules of leguminous plants, which make the resulting nitrogenous compounds available to their host plants.
noun
1.
the conversion of atmospheric nitrogen into nitrogen compounds by certain bacteria, such as Rhizobium in the root nodules of legumes
2.
a process, such as the Haber process, in which atmospheric nitrogen is converted into a nitrogen compound, used esp for the manufacture of fertilizer
nitrogen fixation
The process by which free nitrogen from the air is combined with other elements to form inorganic compounds, such as ammonium ions, which can then be converted by nitrification into nutrients that can be readily absorbed by plants and other organisms for incorporation into more complex organic compounds. During lighting strikes, the atmosphere’s free nitrogen molecules (N2) are broken apart and combine with oxygen to form nitrogen oxides that dissolve in rain to form nitric acid; atmospheric nitrogen is also fixed industrially under high pressure and heat to form ammonia, as in the production of fertilizers. Many species of cyanobacteria and certain other forms of bacteria, especially those that live in the roots of legumes, conduct nitrogen fixation as part of their metabolism, using the enzyme nitrogenase to combine nitrogen with hydrogen as ammonia. All living organisms are dependent on nitrogen fixation and would ultimately die without it. See more at nitrogen cycle.