The current and potential contribution of asymbiotic nitrogen fixation to nitrogen requirements on farms: a review

2001 ◽  
Vol 41 (3) ◽  
pp. 447 ◽  
Author(s):  
I. R. Kennedy ◽  
N. Islam
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Potential Contribution ◽  
Free Living ◽  
Biological Potential ◽  
Asymbiotic Nitrogen Fixation ◽  
Microbial Strains ◽  
The Many ◽  
Short Time ◽  
Biological Nitrogen

Significant levels of biological nitrogen fixation from sources other than nodulated legumes have become a tantalizing prospect for decades. Since the benefit to agriculture of nitrogen fixation from nodulated legumes was established, there have been widespread efforts to promote the use of various asymbiotic diazotrophic bacteria to fix extra nitrogen in soil. Despite much optimism by scientists and farmers, this prospect remains to be realised. Recently, the prospect has been pursued with renewed enthusiasm and several commercialised products have appeared. What are the reasons for this fresh enthusiasm? Are the new products based on realistic assessments of their biological potential? Why has it taken so long to advance to a stage where there is still only limited evidence that verifies hope becoming reality? This review assesses the current contribution from asymbiotic nitrogen fixation and re-assesses the prospects for greater contributions from this source. Among the many aspects of this multi-faceted subject that will be considered are: (i) the range of free-living microbial strains currently contributing to signficant asymbiotic nitrogen fixation; (ii) the significance of nitrogen-fixing microbes naturally associated with plants; (iii) the significance of endophytic systems and their role in sugarcane and other Gramineae; (iv) the possibility of extending this range by introducing new strains or discovering new systems capable of contributing additional nitrogen fixation. The case will be made that conditions providing a sustainable contribution for more than a short time are usually missing in such systems so that spontaneous biological nitrogen fixation is usually transient. It will be argued further that if all the positive factors controlling spontaneity at the biothermodynamic level are exploited, significant biological nitrogen fixation may soon be achieved in some of these systems on farms.

Biological and ecological aspects of nitrogen fixation by free-living micro-organisms

1969 ◽  
Vol 172 (1029) ◽  
pp. 367-388 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Soil Fertility ◽  
Biological Nitrogen Fixation ◽  
Higher Plants ◽  
Symbiotic Association ◽  
Free Living ◽  
Blue Green Algae ◽  
Ecological Aspects ◽  
Micro Organisms ◽  
Biological Nitrogen

Biological nitrogen fixation is a characteristic of certain micro-organisms, which may be free-living or occur in symbiotic association with higher plants. The purpose of this paper is to summarize some of the biological and ecological aspects of nitrogen-fixation by free-living forms. Biochemical aspects have been reviewed in other contributions to this discussion by Drs Wilson, Burris, and Cox & Fay. Nitrogen fixation by heterotrophic micro-organisms has been considered by Jensen (1965); nitrogen fixation by blue-green algae by Fogg & Stewart (1965), and by Stewart (1966, 1969), while Moore (1966) has evaluated the contribution of nitrogen-fixing micro-organisms to soil fertility.

Nitrogen fixation in the high arctic tundra at Sarcpa Lake, Northwest Territories

1985 ◽  
Vol 63 (5) ◽  
pp. 974-979 ◽  
Author(s):  
Jim D. Karagatzides ◽  
Martin C. Lewis ◽  
Herbert M. Schulman
Keyword(s):  
Nitrogen Fixation ◽  
Northwest Territories ◽  
Acetylene Reduction ◽  
Biological Nitrogen Fixation ◽  
Arctic Tundra ◽  
High Arctic ◽  
Fixed Nitrogen ◽  
Free Living ◽  
Blue Green Algae ◽  
Biological Nitrogen

The acetylene reduction assay was used to examine biological nitrogen fixation in the high arctic tundra at Sarcpa Lake, Northwest Territories (68°32′ N, 83°19′ W). The highest rates of acetylene reduction (9.37 ± 3.19 μmol C2H4 m−2 h−1) were in habitats that had a high density of the legumes Oxytropis maydelliana, O. arctobia, and Astragalus alpinus. Nitrogen fixation in the wet soils along the shore of a small lake was similar (8.87 ± 4.35 μmol C2H4 m−2 h−1) because of the blue-green alga Nostoc, which associates with mosses. Free-living blue-green algae and lichens made insignificant contributions to the total nitrogen fixation budget because they were uncommon and fixed nitrogen at a slower rate. Nitrogen-fixing lichens in the area included Stereocaulon arenarium and S. rivulorum. It is concluded that legumes have a significant input to the biological nitrogen fixation budget at Sarcpa Lake.

scholarly journals Soil nitrogen response to shrub encroachment in a degrading semiarid grassland

2018 ◽  
Author(s):  
Thomas Turpin-Jelfs ◽  
Katerina Michaelides ◽  
Joel A. Biederman ◽  
Alexandre M. Anesio
Keyword(s):  
Nitrogen Fixation ◽  
Soil Nitrogen ◽  
Biological Nitrogen Fixation ◽  
Inorganic Nitrogen ◽  
Shrub Encroachment ◽  
Shrub Cover ◽  
Prosopis Velutina ◽  
Free Living ◽  
Semiarid Grassland ◽  
Biological Nitrogen

Abstract. Transitions from grass- to shrub-dominated states in drylands by woody plant encroachment represent significant forms of land cover change with the potential to alter the spatial distribution and cycling of soil resources. Yet an understanding of how this phenomenon impacts the soil nitrogen pool, which is essential to primary production in arid and semiarid systems, is poorly resolved. In this study, we quantified how the distribution and speciation of soil nitrogen, as well as rates of free-living biological nitrogen fixation, changed along a gradient of increasing mesquite (Prosopis velutina Woot.) cover in a semiarid grassland of the Southwestern US. Our results show that site-level concentrations of total nitrogen remain unchanged with increasing shrub cover as losses from intershrub areas (sum of grass and bare-soil cover) are proportional to increases in soils under shrub canopies. However, despite the similar carbon-to-nitrogen ratio and microbial biomass of soil from intershrub and shrub areas at each site, site-level concentrations of inorganic nitrogen increase with shrub cover due to the accumulation of ammonium and nitrate in soils beneath shrub canopies. Using the acetylene reduction assay technique, we found increasing ratios of inorganic nitrogen-to-bioavailable phosphorus inhibit rates of biological nitrogen fixation by free-living soil bacteria. Consequently, we conclude that shrub encroachment has the potential to significantly alter the dynamics of soil nitrogen cycling in dryland systems.

scholarly journals Soil nitrogen response to shrub encroachment in a degrading semi-arid grassland

2019 ◽  
Vol 16 (2) ◽  
pp. 369-381 ◽  
Author(s):  
Thomas Turpin-Jelfs ◽  
Katerina Michaelides ◽  
Joel A. Biederman ◽  
Alexandre M. Anesio
Keyword(s):  
Nitrogen Fixation ◽  
Microbial Biomass ◽  
Soil Nitrogen ◽  
Biological Nitrogen Fixation ◽  
Inorganic Nitrogen ◽  
Shrub Cover ◽  
Prosopis Velutina ◽  
Free Living ◽  
Biological Nitrogen ◽  
Semi Arid

Abstract. Transitions from grass- to shrub-dominated states in drylands by woody plant encroachment represent significant forms of land cover change with the potential to alter the spatial distribution and cycling of soil resources. Yet an understanding of how this phenomenon impacts the soil nitrogen pool, which is essential to primary production in arid and semi-arid systems, is poorly resolved. In this study, we quantified how the distribution and speciation of soil nitrogen, as well as rates of free-living biological nitrogen fixation, changed along a gradient of increasing mesquite (Prosopis velutina Woot.) cover in a semi-arid grassland of the southwestern US. Our results show that site-level concentrations of total nitrogen remain unchanged with increasing shrub cover as losses from inter-shrub areas (sum of grass and bare-soil cover) are proportional to increases in soils under shrub canopies. However, despite the similar carbon-to-nitrogen ratio and microbial biomass of soil from inter-shrub and shrub areas at each site, site-level concentrations of inorganic nitrogen increase with shrub cover due to the accumulation of ammonium and nitrate in soils beneath shrub canopies. Using the acetylene reduction assay technique, we found increasing ratios of inorganic nitrogen to bioavailable phosphorus inhibit rates of biological nitrogen fixation by free-living soil bacteria. Overall, these results provide a greater insight into how grassland-to-shrubland transitions influence the soil N pool through associated impacts on the soil microbial biomass.

Helping plants get more nitrogen from the air

2000 ◽  
Vol 8 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Edward C. Cocking
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Fossil Fuels ◽  
Crop Yields ◽  
Atmospheric Nitrogen ◽  
Fixed Nitrogen ◽  
Free Living ◽  
World Agriculture ◽  
Biological Nitrogen ◽  
Inoculation Technology

Plants cannot themselves obtain their nitrogen from the air but rely mainly on the supply of combined nitrogen in the form of ammonia, or nitrates, resulting from nitrogen fixation by free-living bacteria in the soil or bacteria living symbiotically in nodules on the roots of legumes. Increased crop yields in the twentieth century required this biological nitrogen fixation to be supplemented increasingly by the use of fixed nitrogen from chemical fertilizers. The development of the Haber–Bosch process for catalytically combining atmospheric nitrogen with hydrogen from fossil fuels to produce ammonia enabled increased crop yields. However, energy and environmental concerns arising from the overuse of nitrogenous fertilizers have highlighted the need for plants to obtain more of their nitrogen from the air by biological nitrogen fixation. New systems are being developed for increased biological nitrogen fixation with cereals and other non-legumes by establishing nitrogen-fixing bacteria within their roots. This new inoculation technology is aimed at significantly reducing the use of synthetic nitrogenous fertilizers in world agriculture.

scholarly journals Biological Nitrogen Fixation by Local and Improved Genotypes of Cowpea in Burkina Faso (West Africa): Total Nitrogen Accumulated can be used for Quick Estimation

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Boubié Vincent Bado ◽  
Michel Sedogo ◽  
François Lompo ◽  
Sanoussi Manzo Maman Laminou
Keyword(s):  
Nitrogen Fixation ◽  
Burkina Faso ◽  
Total Nitrogen ◽  
Biological Nitrogen Fixation ◽  
Polynomial Regression ◽  
Cropping Systems ◽  
Isotopic Dilution ◽  
Potential Contribution ◽  
Total N ◽  
Biological Nitrogen

Biological nitrogen fixation (BNF) by legumes is an indicator of their potential contribution to recycling nitrogen in cropping systems. Many techniques exist for the quantitative measurement of legume BNF. The isotopic dilution (ID) methods are the most accurate but are too expensive, time-consuming and require technical expertise. There is a gap between the simple but less accurate Total Nitrogen Difference (TND) method and the Isotopic Dilution (ID) methods. By measuring the BNF of 11 cowpea (Vigna unguiculata) genotypes, this study aimed to develop a simple model as an improved tool for the quick estimation of BNF. Total N accumulated by traditional genotypes from Burkina Faso varied from 23 to 41 kg ha−1. Approximately 40 to 65% of this was nitrogen derived from the atmosphere (Ndfa) when the TND method was used (Ndfa-TND), while the ID method indicated that 29 to 37% of N accumulated was derived from the atmosphere (Ndfa-ID). The TND method overestimated the BNF of high N-yielding genotypes but underestimated the BNF of low N-yielding genotypes (N-accumulated below 31 kg N ha−1). The relationship between N-accumulated and Ndfa-ID was described by a polynomial regression: Yi = 0.0127 Xi2 - 0.5354 Xi + 17.44, where Yi and Xi represent Ndfa-ID and N-accumulated, respectively (P<0.05, R2 =0.92). The model was validated and could be used for quick estimation of BNF directly from the N accumulated.

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