Nitrogen fixation

About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.

Influence of co-inoculation of bacteria-cyanobacteria on crop yield and C–N sequestration in soil under rice crop

Abstract: The performance of three selected bacterial strains—PR3, PR7 and PR10 (Providencia sp., Brevundimonas sp., Ochrobacterium sp.) and three cyanobacterial strains CR1, CR2 and CR3 (Anabaena sp., Calothrix sp., Anabaena sp.), and their combinations was evaluated in a pot experiment with rice variety Pusa-1460, comprising 51 treatments along with recommended fertilizer controls. Highest yield enhancement of 19.02% was recorded in T12 (CR2), over control, while significant enhancement in nitrogen fixing potential was recorded in treatments involving combination of bacterial-cyanobacterial strains—T37 (PR3 + CR1 + CR3) and T21 (PR7 + CR1). Organic carbon was significantly increased in all microbe-inoculated treatments, which could be correlated with microbial biomass carbon values and activities of all the enzymes tested in our study. Also, panicle weight and plant biomass were highly correlated with soil microbial carbon. Comparative evaluation revealed the superior performance of strains CR2, CR1 (both Anabaena sp.) and PR10 (Ochrobacterium sp.) in increasing the growth and grain yield of rice and improving soil health, besides N (nitrogen) savings of 40–80 kg ha−1. The study for the first time illustrated the positive effects of co-inoculation of bacterial and cyanobacterial strains for integrated nutrient management of rice crop.

Nitrogen Fixation by Actinomycete-Nodulated Angiosperms

Abstract: Nitrogen fixation by symbiotic associations between soil bacteria belonging to the actinomycetes and root systems of a diversified group of woody dicotyledonous plants is less generally well known than that by the legume-Rhizobium symbiosis. The fixation of dinitrogen by nodulated legumes is a major mechanism for entry of reduced nitrogen into agricultural lands and, to a much lesser extent, to wooded ecosystems. For forested areas, woodlands, wetlands, and fields, nodulated plants like the alders (Alnus), bog plants like sweet gale (Myrica gale), and roadside and disturbed area invaders such as sweet fern

Seasonal variations in nitrogen-fixation (acetylene reduction) and sulphate-reduction rates in the rhizosphere of Zostera noltii: nitrogen fixation by sulphate-reducing bacteria

Abstract: Nitrogen-fixation (acetylene reduction) rates were measured over an annual cycle in meadows of the seagrass Zostera noltii Hornem in the Bassin d'Arcachon, south-west France, between March 1994 and February 1995, using both slurry and whole-core techniques. Measured rates using the slurry technique consistently overestimated those determined on whole cores, probably due to the release of labile organic carbon sources as a result of root damage during preparation of the slurries. Thus, the whole-core technique may provide a more accurate estimate of in situ activity, since disturbance of physicochemical gradients of oxygen, sulphide, nutrients and the relationship between the plant roots and the rhizosphere microflora is minimised. Rates measured by the whole-core method were 1.8- to 4-fold greater (dependent upon season) in the light than those measured during dark incubations, indicating that organic carbon diffusing from the plant roots during photosynthesis was an important factor in regulating nitrogen fixation in the rhizosphere. Additions of sodium molybdate, a specific inhibitor of sulphate-reducing bacteria (SRB) inhibited acetylene-reduction activity by >80% as measured by both the slurry and whole-core techniques throughout the year, inferring that SRB were the dominant component of the nitrogen-fixing microflora. A mutualistic relationship between Z. noltii and nitrogen-fixing SRB in the rhizosphere, based on the exchange of organic carbon and fixed nitrogen is proposed. Acetylene- and sulphate-reduction rates showed distinct summer peaks which correlated with a reduced availability of ammonium in the sediment and the annual growth cycle of Z. noltii in the basin. Overall, these data indicate that acetylene reduction (nitrogen fixation) activity in the rhizosphere of Z. noltii was regulated both by the availability of organic carbon from the plant roots and maintenance of a low NH 4 + concentration in the vicinity of the plant roots due to efficient assimilation of NH 4 + by Z. noltii during the growth season. Nitrogenfixation rates determined from acetylene-reduction rates measured using the whole-core technique ranged from 0.1 to 7.3 mg N m-2d-1, depending on season, and were calculated to contribute between 0.4 and 1.1 g N m-2yr-1, or 6.3 to 12% of the annual fixed nitrogen requirement of Z. noltii.