nitrogen fixation

nitrogen fixation
nitrogen fixation n
1) the industrial conversion of free nitrogen into combined forms useful esp. as starting materials for fertilizers or explosives
2) the metabolic assimilation of atmospheric nitrogen by soil microorganisms and esp. rhizobia and its release for plant use by nitrification in the soil on the death of the microorganisms

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the union of the free atmospheric nitrogen with other elements to form chemical compounds, such as ammonia and nitrates or amino groups. This occurs primarily through the action of soil bacteria of the genus Rhizobium or Bradyrhizobium in symbiosis with leguminous plants. Nonbiological nitrogen fixation processes include electrical methods and chemical catalysis (Haber process).

Medical dictionary. 2011.