Nitrogen fixation

Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH3) or related nitrogenous compounds. Atmospheric nitrogen, is molecular dinitrogen (N2), a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation converts N2 into ammonia, which is metabolized by most organisms. Nitrogen fixation is essential for life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins, nucleoside triphosphates and nucleic acids. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all chemical compounds that contain nitrogen, which includes some explosives, pharmaceuticals, and dyes.

Process

Nitrogen fixation is carried out naturally in the soil by microorganisms termed diazotrophs that include bacteria such as Azotobacter and archaea. Some nitrogen-fixing bacteria have symbiotic relationships with plant groups, especially legumes. Looser non-symbiotic relationships between diazotrophs and plants are often important in soil fertility.

Industrial nitrogen fixation

Humans also practice nitrogen fixation as a means to fertilize soils. Industrial nitrogen fixation is achieved through the Haber-Bosch process, which utilizes high temperatures and pressures to convert nitrogen gas and hydrogen into ammonia.

Environmental impact

Nitrogen fixation, both natural and human-induced, has environmental impacts. Nitrogen-rich compounds derived from nitrogen fixation can cause a form of pollution known as eutrophication, a harmful overgrowth of plant life.

See also

• Haber process
• Nitrogen cycle
• Nitrogenase

Nitrogen_fixation

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  Diagram of the nitrogen cycle
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  Root nodules on fava bean plant
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  Sectioned alder root nodule gall
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  D. C. Bardwell Study of Nitrogen Fixation
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  Lightning as a natural source of nitrogen fixation