Showing papers on "Nitrogen fixation published in 2021"
TL;DR: In this paper, the importance of Azotobacter species was highlighted as both important free-living N2fixing bacteria and potential bacterial biofertilizer with proven efficacy for plant nutrition and biological soil fertility.
Abstract: Biological nitrogen fixation (BNF) refers to a microbial mediated process based upon an enzymatic "Nitrogenase" conversion of atmospheric nitrogen (N2) into ammonium readily absorbable by roots. N2-fixing microorganisms collectively termed as "diazotrophs" are able to fix biologically N2 in association with plant roots. Specifically, the symbiotic rhizobacteria induce structural and physiological modifications of bacterial cells and plant roots into specialized structures called nodules. Other N2-fixing bacteria are free-living fixers that are highly diverse and globally widespread in cropland. They represent key natural source of nitrogen (N) in natural and agricultural ecosystems lacking symbiotic N fixation (SNF). In this review, the importance of Azotobacter species was highlighted as both important free-living N2-fixing bacteria and potential bacterial biofertilizer with proven efficacy for plant nutrition and biological soil fertility. In addition, we described Azotobacter beneficial plant promoting traits (e.g., nutrient use efficiency, protection against phytopathogens, phytohormone biosynthesis, etc.). We shed light also on the agronomic features of Azotobacter that are likely an effective component of integrated plant nutrition strategy, which contributes positively to sustainable agricultural production. We pointed out Azotobacter based-biofertilizers, which possess unique characteristics such as cyst formation conferring resistance to environmental stresses. Such beneficial traits can be explored profoundly for the utmost aim to research and develop specific formulations based on inoculant Azotobacter cysts. Furthermore, Azotobacter species still need to be wisely exploited in order to address specific agricultural challenges (e.g., nutrient deficiencies, biotic and abiotic constraints) taking into consideration several variables including their biological functions, synergies and multi-trophic interactions, and biogeography and abundance distribution.
93 citations
TL;DR: In this paper, the light-induced soybean TGACG-motif was demonstrated to be an energy-efficient process for symboliotic nitrogen fixation, and the light available to plants has been proposed to be a primary influencer.
Abstract: Symbiotic nitrogen fixation is an energy-expensive process, and the light available to plants has been proposed to be a primary influencer. We demonstrate that the light-induced soybean TGACG-motif...
49 citations
TL;DR: In this article, a genome-wide association study for nodule number identified G. max Nodule Number Locus 1 (GmNNL1), which encodes a new R protein.
Abstract: Symbiosis between soybean (Glycine max) and rhizobia is essential for efficient nitrogen fixation. Rhizobial effectors secreted through the type-III secretion system are key for mediating the interactions between plants and rhizobia, but the molecular mechanism remains largely unknown. Here, our genome-wide association study for nodule number identified G. max Nodule Number Locus 1 (GmNNL1), which encodes a new R protein. GmNNL1 directly interacts with the nodulation outer protein P (NopP) effector from Bradyrhizobium USDA110 to trigger immunity and inhibit nodulation through root hair infection. The insertion of a 179 bp short interspersed nuclear element (SINE)-like transposon into GmNNL1 leads to the loss of function of GmNNL1, enabling bradyrhizobia to successfully nodulate soybeans through the root hair infection route and enhancing nitrogen fixation. Our findings provide important insights into the coevolution of soybean–bradyrhizobia compatibility and offer a way to design new legume–rhizobia interactions for efficient symbiotic nitrogen fixation. Soybean accessions display a variable number of nodules when colonized by rhizobia. The authors identify one locus controlling this trait, a typical TIR–NBS–LRR disease resistance gene called NNL1, and the corresponding bacterial effector called NopP.
36 citations
TL;DR: In this article, the effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated, and it was found that the germination rate was higher with plasma-treated water and more efficient in the presence of metal ions.
Abstract: Nitrogen fixation is crucial for plants as it is utilized for the biosynthesis of almost all biomolecules. Most of our atmosphere consists of nitrogen, but plants cannot straightforwardly assimilate this from the air, and natural nitrogen fixation is inadequate to meet the extreme necessities of global nutrition. In this study, nitrogen fixation in water was achieved by an AC-driven non-thermal atmospheric pressure nitrogen plasma jet. In addition, Mg, Al, or Zn was immersed in the water, which neutralized the plasma-treated water and increased the rate of nitrogen reduction to ammonia due to the additional hydrogen generated by the reaction between the plasma-generated acid and metal. The effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated. The germination rate was found to be higher with plasma-treated water and more efficient in the presence of metal ions. Stem lengths and germination rates were significantly increased with respect to those produced by DI water irrigation. The plants responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll and protein contents. Based on this report, non-thermal plasma reactors could be used to substantially enhance seed germination and seedling growth.
32 citations
TL;DR: The change in root growth strategy contributed to the promotion of biological nitrogen fixation by the rhizobia that live symbiotically with soybean, thereby increasing crop yield.
31 citations
07 Jan 2021
TL;DR: In this paper, the authors discuss various strategies applied to improve rhizobial strains for higher nitrogen fixation efficiency, more competitiveness and enhanced fitness under unfavorable environments, and highlight an approach to integrate the genetically modified elite rhizobia strains in crop production systems.
Abstract: The contribution of biological nitrogen fixation to the total N requirement of food and feed crops diminished in importance with the advent of synthetic N fertilizers, which fueled the “green revolution”. Despite being environmentally unfriendly, the synthetic versions gained prominence primarily due to their low cost, and the fact that most important staple crops never evolved symbiotic associations with bacteria. In the recent past, advances in our knowledge of symbiosis and nitrogen fixation and the development and application of recombinant DNA technology have created opportunities that could help increase the share of symbiotically-driven nitrogen in global consumption. With the availability of molecular biology tools, rapid improvements in symbiotic characteristics of rhizobial strains became possible. Further, the technology allowed probing the possibility of establishing a symbiotic dialogue between rhizobia and cereals. Because the evolutionary process did not forge a symbiotic relationship with the latter, the potential of molecular manipulations has been tested to incorporate a functional mechanism of nitrogen reduction independent of microbes. In this review, we discuss various strategies applied to improve rhizobial strains for higher nitrogen fixation efficiency, more competitiveness and enhanced fitness under unfavorable environments. The challenges and progress made towards nitrogen self-sufficiency of cereals are also reviewed. An approach to integrate the genetically modified elite rhizobia strains in crop production systems is highlighted.
29 citations
01 Jan 2021
TL;DR: Analysis of significant OTUs showed distinct nifH-expressing microbial communities at the two field locations, as well as a unique community in roots of unfertilized soil at Frederick that exhibited the highest rates of nitrogen fixation.
Abstract: The use of synthetic nitrogen fertilizers to grow biofuel crops adds to the economic and environmental costs of biomass production. Biological nitrogen fixation provides an alternative, eco-friendl...
28 citations
TL;DR: Wang et al. as mentioned in this paper have isolated several sugarcane rhizosphere bacteria, and 27 of them were examined for N-fixation, plant growth promotion, and antifungal activity.
Abstract: Sugarcane is a major crop in tropical and subtropical regions of the world. In China, the application of large amounts of nitrogen (N) fertilizer to boost sugarcane yield is commonplace, but it causes substantial environmental damages, particularly soil, and water pollution. Certain rhizosphere microbes are known to be beneficial for sugarcane production, but much of the sugarcane rhizosphere microflora remains unknown. We have isolated several sugarcane rhizosphere bacteria, and 27 of them were examined for N-fixation, plant growth promotion, and antifungal activity. 16S rRNA gene sequencing was used to identify these strains. Among the isolates, several strains were found to have a relatively high activity of nitrogenase and ACC deaminase, the enzyme that reduces ethylene production in plants. These strains were found to possess nifH and acdS genes associated with N-fixation and ethylene production, respectively. Two of these strains, Pantoea dispersa-AA7 and Enterobacter asburiae-BY4 showed maximum plant growth promotion (PGP) and nitrogenase activity, and thus they were selected for detailed analysis. The results show that they colonize different sugarcane tissues, use various growth substrates (carbon and nitrogen), and tolerate various stress conditions (pH and osmotic stress). The positive effect of AA7 and BY4 strains on nifH and stress-related gene (SuCAT, SuSOD, SuPAL, SuCHI, and SuGLU) expression and the induction of defense-related processes in two sugarcane varieties, GT11 and GXB9, showed their potential for stress amelioration and PGP. Both bacterial strains increased several sugarcane physiological parameters. i.e., plant height, shoot weight, root weight, leaf area, chlorophyll content, and photosynthesis, in plants grown under greenhouse conditions. The ability of rhizobacteria on N-fixing in sugarcane was also confirmed by a 15N isotope-dilution study, and the estimate indicates a contribution of 21-35% of plant nitrogen by rhizobacterial biological N fixation (BNF). This is the first report of sugarcane growth promotion by N-fixing rhizobacteria P. dispersa and E. asburiae strains. Both strains could be used as biofertilizer for sugarcane to minimize nitrogen fertilizer use and better disease management.
27 citations
TL;DR: In this article, the long-term effects of partial substitution of mineral N by organic fertilizers on diazotroph abundance and composition in double rice cropping systems were investigated through high-throughput sequencing, network analysis, and 15N2 labelling methods.
Abstract: Free-living nitrogen fixation (FLNF) by diazotrophs is a ubiquitous renewable resource and may constitute an attractive viable solution to the problem of environmental degradation caused by nitrogen over-fertilization. However, the biotic and abiotic control mechanisms of free-living nitrogen fixation are poorly understood. Moreover, there is rare information to link the composition and functions of diazotrophic communities; additionally, there are insufficient or inadequate predictors of the potential N fixation rate (PNFR) to help improve fertilization strategies. Here, through high-throughput sequencing, network analysis, and 15N2 labelling methods, we investigated the long-term effects of partial substitution of mineral N by organic fertilizers on diazotroph abundance and composition in double rice cropping systems. The field trial was conducted for 34 years and included five treatments: control without fertilizer (CK); only mineral NPK fertilizer (NPK); 70% inorganic N + 30% organic N + PK (NPKM1); 50% inorganic N + 50% organic N + PK (NPKM2); 30% inorganic N + 70% organic N + PK (NPKM3). Our results revealed that at the same nutrient input level, increasing the percentage of organic N substitution reduced diazotrophic abundance. Compared with the CK and NPK treatments, the organic substitution regimes reduced the fluctuation range of the PNFR between the early and late rice growing seasons. NH4+-N was the primary factor that negatively correlated (p
27 citations
TL;DR: In this article, a nitrogen-vacancy pothole-rich few-layer g-C3N4 was synthesized through ice-water bath ultrasound and rapid secondary sintering.
26 citations
TL;DR: In this paper, a metabolic model derived from genome-scale datasets was used to show that carbon polymer synthesis and alanine secretion by bacteroids facilitate redox balance in microaerobic nodules.
Abstract: Rhizobia induce nodule formation on legume roots and differentiate into bacteroids, which catabolize plant-derived dicarboxylates to reduce atmospheric N2 into ammonia. Despite the agricultural importance of this symbiosis, the mechanisms that govern carbon and nitrogen allocation in bacteroids and promote ammonia secretion to the plant are largely unknown. Using a metabolic model derived from genome-scale datasets, we show that carbon polymer synthesis and alanine secretion by bacteroids facilitate redox balance in microaerobic nodules. Catabolism of dicarboxylates induces not only a higher oxygen demand but also a higher NADH/NAD+ ratio than sugars. Modeling and 13C metabolic flux analysis indicate that oxygen limitation restricts the decarboxylating arm of the tricarboxylic acid cycle, which limits ammonia assimilation into glutamate. By tightly controlling oxygen supply and providing dicarboxylates as the energy and electron source donors for N2 fixation, legumes promote ammonia secretion by bacteroids. This is a defining feature of rhizobium-legume symbioses.
TL;DR: In this paper, the authors have brought together the latest findings on flavonoids biosynthesis and ureide metabolism in several legume plant species and emphasized how flavonoid induce nod genes in rhizobia, affecting chemotaxis, nodulation, ureides production, growth and yield of legume plants.
TL;DR: In this paper, the authors describe the identification, development, and deployment of the first microbial product optimized using synthetic biology tools to enable BNF for corn (Zea mays) in fertilized fields, demonstrating the successful, safe commercialization of root-associated diazotrophs and realizing the potential of BNF to replace and reduce synthetic nitrogen fertilizer use in production agriculture.
Abstract: Agricultural productivity relies on synthetic nitrogen fertilizers, yet half of that reactive nitrogen is lost to the environment. There is an urgent need for alternative nitrogen solutions to reduce the water pollution, ozone depletion, atmospheric particulate formation, and global greenhouse gas emissions associated with synthetic nitrogen fertilizer use. One such solution is biological nitrogen fixation (BNF), a component of the complex natural nitrogen cycle. BNF application to commercial agriculture is currently limited by fertilizer use and plant type. This paper describes the identification, development, and deployment of the first microbial product optimized using synthetic biology tools to enable BNF for corn (Zea mays) in fertilized fields, demonstrating the successful, safe commercialization of root-associated diazotrophs and realizing the potential of BNF to replace and reduce synthetic nitrogen fertilizer use in production agriculture. Derived from a wild nitrogen-fixing microbe isolated from agricultural soils, Klebsiella variicola 137-1036 ("Kv137-1036") retains the capacity of the parent strain to colonize corn roots while increasing nitrogen fixation activity 122-fold in nitrogen-rich environments. This technical milestone was then commercialized in less than half of the time of a traditional biological product, with robust biosafety evaluations and product formulations contributing to consumer confidence and ease of use. Tested in multi-year, multi-site field trial experiments throughout the U.S. Corn Belt, fields grown with Kv137-1036 exhibited both higher yields (0.35 ± 0.092 t/ha ± SE or 5.2 ± 1.4 bushels/acre ± SE) and reduced within-field yield variance by 25% in 2018 and 8% in 2019 compared to fields fertilized with synthetic nitrogen fertilizers alone. These results demonstrate the capacity of a broad-acre BNF product to fix nitrogen for corn in field conditions with reliable agronomic benefits.
TL;DR: Investigation of the effects of different long-term fertilization on the diazotrophic community in a vertisol using real-time quantitative polymerase chain reaction (PCR) and MiSeq sequencing indicated that organic amendments are beneficial to diazOTrophic activity, abundance, OTU richness, alpha-diversity, and the d Diazotrophic communities' potential interactions.
TL;DR: In this article, the role of root exudates in Phomopsis liquidambaris-inoculated peanuts nodulation and nitrogen fixation has been explored, and the root exude profile was compared with root exuding profile of uninoculating and un-inculated plants and found that root exudes altered the concentrations of phenolic acids, flavonoids, organic acids and amino acids.
TL;DR: In this paper, the authors examined the potential rate of asymbiotic N2 fixation, nifH gene abundance, the composition and co-occurrence network of diazotrophic community in an acidic red soil received different organic and inorganic fertilization regimes for more than 40 years.
TL;DR: In this article, the role of chemical bond in catalytic nitrogen fixation has been clarified by summarizing and analyzing the recent development of nitrogen fixation research, all from a chemical bond perspective.
Abstract: Ammonia (NH3 ) and nitrates are essential for human society because of their widespread utilization for producing medicines, fibers, fertilizers, etc. In recent years, the development on nitrogen fixation under mild reaction conditions has attracted much attention. However, the very low conversion efficiency and ambiguous catalytic mechanism remain the major hurdles for the research of nitrogen fixation. This review aims to clarify the role of chemical bond in catalytic nitrogen fixation by summarizing and analyzing the recent development of nitrogen fixation research. In detail, the atomic-scale mechanism of nitrogen fixation reaction, the various methods to improve the nitrogen fixation performance, and the computational investigation of nitrogen fixation are discussed, all from a chemical bond perspective. It is hoped that this review could trigger more profound pondering and deeper exploration in the field of catalytic nitrogen fixation.
08 Jul 2021
TL;DR: In this paper, the basic principles of plasma nitrogen fixation technology and its associated research progress are reviewed and compared, and the prospect of nitrogen fixation using low-temperature plasma in the future was proposed.
Abstract: Nitrogen fixation is essential for all forms of life, as nitrogen is required to biosynthesize fundamental building blocks of creatures, plants, and other life forms. As the main method of artificial nitrogen fixation, Haber–Bosch process (ammonia synthesis) has been supporting the agriculture and chemical industries since the 1910s. However, the disadvantages inherent to the Haber–Bosch process, such as high energy consumption and high emissions, cannot be ignored. Therefore, developing a green nitrogen fixation process has always been a research hotspot. Among the various technologies, plasma-assisted nitrogen fixation technology is very promising due to its small scale, mild reaction conditions, and flexible parameters. In the present work, the basic principles of plasma nitrogen fixation technology and its associated research progress are reviewed. The production efficiency of various plasmas is summarized and compared. Eventually, the prospect of nitrogen fixation using low-temperature plasma in the future was proposed.
TL;DR: A ‘1+n−N’ model is proposed to promote the function of symbiotic nitrogen fixation (SNF) in agricultural practice, where ’1’ refers to appreciate rhizobium; ‘+n’ means the addition of multiple trace elements and PGPR bacteria; and ‘− N’ implies the reduction of chemical nitrogen fertilizer.
Abstract: Currently, symbiotic rhizobia (sl., rhizobium) refer to the soil bacteria in α- and β-Proteobacteria that can induce root and/or stem nodules on some legumes and a few of nonlegumes. In the nodules, rhizobia convert the inert dinitrogen gas (N2 ) into ammonia (NH3 ) and supply them as nitrogen nutrient to the host plant. In general, this symbiotic association presents specificity between rhizobial and leguminous species, and most of the rhizobia use lipochitooligosaccharides, so called Nod factor (NF), for cooperating with their host plant to initiate the formation of nodule primordium and to inhibit the plant immunity. Besides NF, effectors secreted by type III secretion system (T3SS), exopolysaccharides and many microbe-associated molecular patterns in the rhizobia also play important roles in nodulation and immunity response between rhizobia and legumes. However, the promiscuous hosts like Glycine max and Sophora flavescens can nodulate with various rhizobial species harbouring diverse symbiosis genes in different soils, meaning that the nodulation specificity/efficiency might be mainly determined by the host plants and regulated by the soil conditions in a certain cases. Based on previous studies on rhizobial application, we propose a '1+n-N' model to promote the function of symbiotic nitrogen fixation (SNF) in agricultural practice, where '1' refers to appreciate rhizobium; '+n' means the addition of multiple trace elements and PGPR bacteria; and '-N' implies the reduction of chemical nitrogen fertilizer. Finally, open questions in the SNF field are raised to future think deeply and researches.
TL;DR: In this paper, actinobacteria isolated from different niches and having PGP activities were used in co-inoculation experiments with rhizobia in Medicago sativa plants rhizosphere submitted to salt stress.
Abstract: Biotic and abiotic stresses are severely limiting plant production and productivity. Of notable importance is salt stress that not only limits plant growth and survival, but affects the soil fertility and threatens agricultural ecosystems sustainability. The problem is exacerbated in fragile arid and semi-arid areas where high evaporation, low precipitation and the use of salty water for irrigation is accelerating soil salinization. Legumes, considered very nutritious foods for people and providing essential nutrients for ecosystems are a fundamental element of sustainable agriculture. They can restore soil health by their ability to fix nitrogen in a symbiotic interaction with the rhizobia of the soil. However, salt stress is severely limiting productivity and nitrogen fixation ability in legumes. Plant growth-promoting rhizobacteria (PGPR) and mainly actinobacteria promote plant growth by producing phytohormones, siderophores, antibiotics and antifungal compounds, solubilizing phosphate and providing antagonism to phytopathogenic microorganisms. In addition, actinobacteria have beneficial effects on nodulation and growth of legumes. In this study, actinobacteria isolated from different niches and having PGP activities were used in co-inoculation experiments with rhizobia in Medicago sativa plants rhizosphere submitted to salt stress. The results indicate that drought- and salinity-tolerant Actinobacteria with multiple PGP traits can potentially increase alfalfa growth under saline conditions, in the presence or absence of symbiotic rhizobial bacteria. Actinobacteria discovered in this study can, therefore, be suitable biofertilizers in the formulation of agricultural products improving plant development, health and productivity in saline soils, a necessary alternative for modern agriculture and sustainable development.
TL;DR: The role of diazotrophs in coral physiology and reef biogeochemistry remains poorly understood, in part because N2 fixation rates and dizotrophic community composition have only been jointly analyzed in the tissue of one tropical coral species as mentioned in this paper.
Abstract: The role of diazotrophs in coral physiology and reef biogeochemistry remains poorly understood, in part because N2 fixation rates and diazotrophic community composition have only been jointly analyzed in the tissue of one tropical coral species. We performed field-based 15N2 tracer incubations during nutrient-replete conditions to measure diazotroph-derived nitrogen (DDN) assimilation into three species of scleractinian coral (Pocillopora acuta, Goniopora columna, Platygyra sinensis). Using multi-marker metabarcoding (16S rRNA, nifH, 18S rRNA), we analyzed DNA- and RNA-based communities in coral tissue and skeleton. Despite low N2 fixation rates, DDN assimilation supplied up to 6% of the holobiont’s N demand. Active coral-associated diazotrophs were chiefly Cluster I (aerobes or facultative anaerobes), suggesting that oxygen may control coral-associated diazotrophy. Highest N2 fixation rates were observed in the endolithic community (0.20 µg N cm−2 per day). While the diazotrophic community was similar between the tissue and skeleton, RNA:DNA ratios indicate potential differences in relative diazotrophic activity between these compartments. In Pocillopora, DDN was found in endolithic, host, and symbiont compartments, while diazotrophic nifH sequences were only observed in the endolithic layer, suggesting a possible DDN exchange between the endolithic community and the overlying coral tissue. Our findings demonstrate that coral-associated diazotrophy is significant, even in nutrient-rich waters, and suggest that endolithic microbes are major contributors to coral nitrogen cycling on reefs.
TL;DR: The results show that N-induced environmental changes have considerable influence on the composition and potential functions of soil bacterial and fungal communities, which are likely to be dependent on interactions between plants and soil.
Abstract: Nitrogen (N) fertilizer is applied to the soil to increase the nutrient level and plant productivity, but the effects of N addition on the soil microbial community diversity and functions are unclear. This study aimed to determine how changes in soil N influence soil microbial community diversity and potential functions. We evaluated plant characteristics, soil chemical properties, microbial composition, and potential functions (N-fixation and functional fungal guild) after 3 years of urea fertilization at four different levels (0, 25, 50, and 100 kg N ha−1 year−1) in a semiarid grassland in China. Compositions of bacterial and fungal communities were determined by high-throughput sequencing, and their potential functions were predicted by comparing their data with those in the Tax4Fun and FUNGuild databases, respectively. Compared with the grassland without N input (N0), N fertilization significantly reduced soil bacterial diversity, possibly by reducing plant diversity. Fungal diversity increased with N fertilization and peaked in the N50 treatment, while the aboveground biomass showed a parallel increase and peak. A lower abundance of nif genes was found in the N100 than in the N0 treatment because the enhanced NO3− and NH4+ content alleviated the dependence of plants on biological N-fixation and reduced the N-fixation potential. N fertilization increased the relative abundance of saprotrophs (wood, plant, and dung saprotrophs) and pathogens (plant and animal pathogens). However, this promotion could be weakened when the excessive N fertilization was applied due to the lower abundance in the N100 than in the N50 treatment, and these changes could be attributed to the variation in aboveground biomass and soil organic C. Changes in the abundance of arbuscular mycorrhizal fungi were related to their host plants, exhibiting a transient increase in the N25 compared to the N0 treatment and then sharply decreasing. Our results show that N-induced environmental changes have considerable influence on the composition and potential functions of soil bacterial and fungal communities, which are likely to be dependent on interactions between plants and soil.
TL;DR: This work estimated the contribution of dense blooms of diazotrophic filamentous cyanobacteria to nitrogen fixation in the Baltic Sea by combining two decades of cyanobacterial biovolume monitoring data with recently measured genera-specific nitrogen fixation rates.
Abstract: Dense blooms of diazotrophic filamentous cyanobacteria are formed every summer in the Baltic Sea. We estimated their contribution to nitrogen fixation by combining two decades of cyanobacterial biovolume monitoring data with recently measured genera-specific nitrogen fixation rates. In the Bothnian Sea, estimated nitrogen fixation rates were 80 kt N year-1, which has doubled during recent decades and now exceeds external loading from rivers and atmospheric deposition of 69 kt year-1. The estimated contribution to the Baltic Proper was 399 kt N year-1, which agrees well with previous estimates using other approaches and is greater than the external input of 374 kt N year-1. Our approach can potentially be applied to continuously estimate nitrogen loads via nitrogen fixation. Those estimates are crucial for ecosystem adaptive management since internal nitrogen loading may counteract the positive effects of decreased external nutrient loading.
TL;DR: Relationships between salt tolerance and biological nitrogen fixation in A. sparsifolia explains how these species can increase soil nutrient availability across differing dryland environments, and illustrates a possible strategy whereby dryland legumes enhance their adaptability to saline environments by both building symbiotic associations with Rhizobium and utilizing readily available N when salt stress is less prohibitive.
TL;DR: The specialized dorsal leaves of the fern possess a cavity that harbors cyanobacteria capable of fixing atmospheric nitroge... is a free-floating hydrophyte fern grown in temperate and tropical regions.
Abstract: is a free-floating hydrophyte fern grown in temperate and tropical regions. The specialized dorsal leaves of the fern possess cavity that harbors cyanobacteria capable of fixing atmospheric nitroge...
TL;DR: In this paper, the authors describe the role of the master regulator NODULE INCEPTION (NIN), which controls many aspects of nodule initiation, including the initiation time of the nodule itself.
Abstract: Legume nodules create an environment for intracellular bacterial symbionts to fix atmospheric nitrogen. The master regulator NODULE INCEPTION (NIN) controls many aspects of nodule initiation, and w...
TL;DR: In this article, a promising approach to achieve the NH3 synthesis under mild conditions has been proposed by using bioelectrochemical nitrogen fixation (e-BNF) as a promising method.
Abstract: Increasing attention has been paid to bioelectrochemical nitrogen fixation (e-BNF) as a promising approach to achieve the NH3 synthesis under mild conditions. However, currently developed microbial...
TL;DR: The amount of nitrogen entering soil through the mineralization of crop residues ranges from 15 to 45 kg in cereal residues and from 80 to 144 kg in winter rape residues as mentioned in this paper, which can increase the nitrogen content in soil by 30 to 50 kg/ha/year.
Abstract: Nitrogen (N) is widely distributed in the lithosphere, hydrosphere, atmosphere and biosphere. It is a basic component of every plant cell as well as microorganisms, as a component of proteins, nucleic acids and chlorophyll. It enters soil with organic and mineral fertilizers, plant and animal residues and biological nitrogen fixation. There are various forms of nitrogen in soil, and this element is usually transformed by microorganisms. The transformation of nitrogen compounds (ammonification, nitrification and immobilization) is significantly influenced by climatic conditions and the physicochemical properties of soil. Microbial mineralization of nitrogen organic matter results in the enrichment of soil with this element, which is necessary to generate a yield. The amount of nitrogen entering soil through the mineralization of crop residues ranges from 15 to 45 kg N/ha in cereal residues and from 80 to 144 kg N/ha in winter rape residues. Biological nitrogen fixation can increase the nitrogen content in soil by 30–50 kg/ha/year. In recent decades, the mismanagement of mineral fertilizers has drastically changed the natural balance of the nitrogen cycle. Every year huge amounts of nitrogen compounds enter the aquatic ecosystems and cause their eutrophication. That is why it is important to have adequate knowledge of sustainable fertilization so as to practice integrated crop management.