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Nitrogen fixation is a chemical process by which molecular nitrogen (N
2), which has a strong triple covalent bond, is converted into ammonia (NH
3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).
In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem—an ecological system managed and shaped by humans. Cover crops can increase microbial activity in the soil, which has a positive effect on nitrogen availability, nitrogen uptake in target crops, and crop yields. Cover crops may be an off-season crop planted after harvesting the cash crop. Cover crops are nurse crops in that they increase the survival of the main crop being harvested, and are often grown over the winter. In the United States, cover cropping may cost as much as $35 per acre.
Diazotrophs are bacteria and archaea that fix atmospheric nitrogen(N2) in the atmosphere into bioavailable forms such as ammonia.
Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil. In addition to being a model organism for studying diazotrophs, it is used by humans for the production of biofertilizers, food additives, and some biopolymers. The first representative of the genus, Azotobacter chroococcum, was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck. Azotobacter species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants.
Biological soil crusts are communities of living organisms on the soil surface in arid and semi-arid ecosystems. They are found throughout the world with varying species composition and cover depending on topography, soil characteristics, climate, plant community, microhabitats, and disturbance regimes. Biological soil crusts perform important ecological roles including carbon fixation, nitrogen fixation and soil stabilization; they alter soil albedo and water relations and affect germination and nutrient levels in vascular plants. They can be damaged by fire, recreational activity, grazing and other disturbances and can require long time periods to recover composition and function. Biological soil crusts are also known as biocrusts or as cryptogamic, microbiotic, microphytic, or cryptobiotic soils.
Paenibacillus polymyxa, also known as Bacillus polymyxa, is a Gram-positive bacterium capable of fixing nitrogen. It is found in soil, plant tissues, marine sediments and hot springs. It may have a role in forest ecosystems and potential future applications as a biofertilizer and biocontrol agent in agriculture.
Herbaspirillum is a genus of bacteria, including the nitrogen-fixing Herbaspirillum lusitanum.
Bradyrhizobium is a genus of Gram-negative soil bacteria, many of which fix nitrogen. Nitrogen fixation is an important part of the nitrogen cycle. Plants cannot use atmospheric nitrogen (N2); they must use nitrogen compounds such as nitrates.
Rhizobacteria are root-associated bacteria that can have a detrimental, neutral or beneficial effect on plant growth. The name comes from the Greek rhiza, meaning root. The term usually refers to bacteria that form symbiotic relationships with many plants (mutualism). Rhizobacteria are often referred to as plant growth-promoting rhizobacteria, or PGPRs. The term PGPRs was first used by Joseph W. Kloepper in the late 1970s and has become commonly used in scientific literature.
Actinorhizal plants are a group of angiosperms characterized by their ability to form a symbiosis with the nitrogen fixing actinomycetota Frankia. This association leads to the formation of nitrogen-fixing root nodules.
Microbial inoculants, also known as soil inoculants or bioinoculants, are agricultural amendments that use beneficial rhizosphericic or endophytic microbes to promote plant health. Many of the microbes involved form symbiotic relationships with the target crops where both parties benefit (mutualism). While microbial inoculants are applied to improve plant nutrition, they can also be used to promote plant growth by stimulating plant hormone production. Although bacterial and fungal inoculants are common, inoculation with archaea to promote plant growth is being increasingly studied.
Johanna Liesbeth Kubelka Döbereiner was a Brazilian agronomist and pioneer in soil biology.
Herbaspirillum seropedicae is a betaproteobacteria which is an endophytic diazotroph and forms nitrogen-fixing associations with maize, rice, sorghum, sugar cane, bananas (Musa) and pineapple. H. seropedicae is a potential nitrogen biofertilizer. Studies have shown that rice with H. seropedicae inoculated increases the yield to an equivalent of 40 kg N/ha.
Azoarcus olearius is a species of bacteria. It is a nitrogen-fixing bacteria. Its cells are Gram-negative, motile and rod-shaped, surrounded by a thin capsule. Its type strain is DQS-4T.
A nitrogen fixation package is a piece of research equipment for studying nitrogen fixation in plants. One product of this kind, the Q-Box NF1LP made by Qubit Systems, operates by measuring the hydrogen (H2) given off in the nitrogen-fixing chemical reaction enabled by nitrogenase enzymes.
Azospirillum is a Gram-negative, microaerophilic, non-fermentative and nitrogen-fixing bacterial genus from the family of Rhodospirillaceae. Azospirillum bacteria can promote plant growth.
Paludibacter propionicigenes is a Gram-negative, strictly anaerobic, non-spore-forming and non-motile bacterium from the genus of Paludibacter which has been isolated from rice plant residue in Yamagata on Japan. Paludibacter propionicigenes produces propionate and acetate from glucose fermentation and is classified as a saccharolytic fermenter.
Azorhizophilus is a genus from the family of Pseudomonadaceae, with one known species.
Flexivirga alba is a non-spore-forming bacterium from the genus of Flexivirga which has been isolated from soil near a wastewater treatment plant in Seki in Japan.
Arenimonas oryziterrae is a Gram-negative, aerobic and rod-shaped bacterium from the genus of Arenimonas which has been isolated from rhizosphere soil from a rice plant from Jinju in Korea.
References
- 1 2 Parte, A.C. "Azorhizophilus". LPSN .
- ↑ "Azorhizophilus paspali Taxon Passport - StrainInfo". www.straininfo.net.[ dead link ]
- 1 2 "Azorhizophilus paspali (Azotobacter paspali)". www.uniprot.org.
- ↑ Parker, Charles Thomas; Garrity, George M. "Nomenclature Abstract for Azorhizophilus paspali (Döbereiner 1966) Thompson and Skerman 1981". The NamesforLife Abstracts. doi:10.1601/nm.9100 (inactive 2024-04-17).
{{cite journal}}: CS1 maint: DOI inactive as of April 2024 (link) - ↑ "Details: DSM-2283". Leibniz-Institut DSMZ - Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH.
- ↑ V., Vancura; F., Kunc (1989). Interrelationships Between Microorganisms and Plants in Soil. Elsevier. ISBN 9780080869865.