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.

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.

Yield and biological nitrogen fixation of cowpea varieties in the semi-arid region of Brazil

2012 ◽  
Vol 45 ◽  
pp. 109-114 ◽  
Author(s):  
Ana Dolores Santiago de Freitas ◽  
Acácia Fernandes Silva ◽  
Everardo Valadares de Sá Barretto Sampaio
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Arid Region ◽  
Cowpea Varieties ◽  
Semi Arid Region ◽  
Biological Nitrogen ◽  
Semi Arid

Contribution of biological nitrogen fixation to cowpea: a strategy for improving grain yield in the semi-arid region of Brazil

2003 ◽  
Vol 38 (6) ◽  
pp. 333-339 ◽  
Author(s):  
L. M. V. Martins ◽  
G. R. Xavier ◽  
F. W. Rangel ◽  
J. R. A. Ribeiro ◽  
M. C. P. Neves ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Grain Yield ◽  
Biological Nitrogen Fixation ◽  
Arid Region ◽  
Semi Arid Region ◽  
Biological Nitrogen ◽  
Semi Arid

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 Nitrogen utilization and transformation ofStenotrophomonas maltophiliaW-6 with nitrogen-fixing ability

2018 ◽  
Author(s):  
Shutong Wang ◽  
Yi Xu ◽  
Zhenlun Li
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Cycle ◽  
Biological Nitrogen Fixation ◽  
Stenotrophomonas Maltophilia ◽  
Inorganic Nitrogen ◽  
Nitrate Removal ◽  
Nitrogen Utilization ◽  
Purple Soil ◽  
Nitrogen Fixing ◽  
Biological Nitrogen

AbstractStrain W-6 was isolated from the purple soil and successfully identifed asStenotrophomonas maltophiliaand used for the investigation on nitrogen utilization. Strain W-6 was monitored with the ability of biological nitrogen fixation when N2was used for the sole nitrogen source, and yet nitrogenase activity would be inhibited in the presence of extra nitrogen. Moreover, Strain W-6 could utilize NO3−, NO2−and NH4+for cell growth through assimilation, but unable to convert them to atmospheric nitrogen. Meantime, accumulation of nitrite was observed during the nitrate removal process, and the optimal conditions for nitrate removal were temperature of 20°C, shaking speed of 150 rpm, sodium succinate as the carbon source and C/N of 12. The experimental results indicate thatStenotrophomonas maltophiliautilize W-6 could utilize not only N2but also other nitrogen sources directly as its N substance. Therefore, heterotrophicAzotobactermay possess a great significance to nitrogen cycle except in biological nitrogen fixation.ImportanceAzotobacterspp. are found in soils worldwide, with features not simply for the nitrogen fixation, but for the energy metabolism relevant to agriculture. However, the role ofAzotobacterpotential in the function of nitrogen cycle except in biological nitrogen fixation is largely unknown. As such, whether bacteria utilize either inorganic nitrogen or organic nitrogen has remained obscure. The present studies indicate thatStenotrophomonas maltophiliaW-6 could highly efficient utilize nitrate, nitrite and ammonium etc. N substance and detect NH4+as final product. The transport velocities of nitrate-N to nitrite-N was quickly without gaseous nitrogen was produced. We probed the relationship between biological nitrogen fixation and N cycle via N conversion processes byS. maltophiliaW-6 with nitrogen-fixing ability

scholarly journals BIOLOGICAL NITROGEN FIXATION STABILITY OF COWPEA CULTIVARS WITH TROPICAL SEMI-ARID RHIZOBIAL STRAINS

2021 ◽  
Vol 34 (2) ◽  
pp. 359-369
Author(s):  
AMANDA CORDEIRO DE MELO SOUZA ◽  
THIAGO PONTES LIRA ◽  
ANTONIO FÉLIX DA COSTA ◽  
FELIPE JOSÉ CURY FRACETTO ◽  
GISELLE GOMES MONTEIRO FRACETTO ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Dry Matter ◽  
Block Design ◽  
Nitrogen Accumulation ◽  
Arid Soils ◽  
Cowpea Cultivars ◽  
Nodule Number ◽  
Biological Nitrogen ◽  
Semi Arid

ABSTRACT Cowpeas (Vigna unguiculata L. Walp) are an economically and socially important legume in northern and north-eastern Brazil and can establish effective symbiosis with nitrogen-fixing bacteria. We evaluated the symbiotic compatibility and efficiency of rhizobial strains from Pernambuco semi-arid soils and determined their symbiotic stability on the IPA-206, BR 17-Gurguéia, and BRS Novaera cultivars, selected for different environments. The experiment was conducted in a greenhouse to evaluate a 3 × 28 factorial arrangement (cultivars selected for different environments × inoculation with the currently recommended strain, uninoculated plants with or without mineral nitrogen, and 25 rhizobial strains from semi-arid soils) in a randomized block design with four replicates. We determined nodule number, shoot and root dry matter, nodule dry matter by nodule number, nitrogen accumulated in the shoot by nodule dry matter, nitrogen content and accumulation in the shoot, relative efficiency of the recommended strain based on nitrogen accumulation, and shoot dry matter. Overall, the cultivars responded differently to different strains and cultivar biological nitrogen fixation potential. Strains G7.85 and BR 3262 showed potential for biological nitrogen fixation. BR 3262 was confirmed to be adequate for inoculation of different cowpea cultivars.

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