Nitrogen-fixing Microorganisms Research Articles

Biofertilizer based on fish waste increases the yield of Vigna unguiculata L. Walp, Zea mays L., and the rhizospheric microbiota

Crops of Vigna unguiculata L. “cowpea” and Zea mays L. “corn” require chemical fertilizers for proper growth and development; however, its inadequate application contaminates the environment, creating the need to search new alternatives that reduce its impact. Due to this, the objective of this research was to determine the effect of a biofertilizer from fish wastes on the yield of cowpea and corn, and its effect on their rhizospheric microbiota. The physicochemical and biological characteristics of the biofertilizer were determined, and then was applied on the field under a completely randomized block design with six treatments: absolute control, chemical control, biofertilizer at 1%, 1.25%, 1.5% and 1.25% plus chemical fertilizer. The application of biofertilizer at 1, 1.25 and 1.5% increased the height, root length and yield of cowpea; however, the increase percentages were lower than those obtained with chemical fertilizer and the biofertilizer at 1.25% plus chemical fertilizer. In the case of corn, all treatments with biofertilizer increased the growth and yield of aerial biomass compared to the control, and the percentages of increase exceeded the chemical fertilizer in terms of the number of leaves, length and root biomass. In addition, the biofertilizer increased the microbial fertility of the soil expressed as the number of colony-forming units of nitrogen-fixing and phosphate-solubilizing microorganisms per gram of soil in both crops. In conclusion, a positive effect of the biofertilizer from fish wastes was evidenced, which increased the yield of cowpea and corn, as well as an increase in soil microbial fertility.

Investigation of nitrogen fixation activity soybeans plants by mineral fertilizers foliar treatment

The results of the study of nitrogen-fixing activity during foliar treatment of vegetative soybean plants with liquid mineral fertilizers containing macro-microelements in various forms in the foothill zone of Kabardino-Balkaria are presented. The object of research is the early ripe soybean variety SK Veda. The soil of the experimental plot is a leached, medium-thick, low-humus, heavy loamy chernozem on carbonate clays, with a humus content in the arable layer of 3.1 %, pHkcl 5.0, mobile phosphorus 7.5 and exchangeable potassium 8.0 mg/100 g of soil. Encrustation of soybean seeds was carried out using a specific film-forming agent based on soybean phosphatides with the inoculant Nitrofix. The results of studies for 2020-2022 are given. with an assessment of the dynamics of the formation of the symbiotic apparatus by the number of nodules (pcs/m2) and by the mass of nodules (g/m2) in ontogeny of the macrosymbiont. The peak of nodule formation in soybean plants of the SK Veda variety fell on the flowering phase. The highest nodulation rates were noted in the control variant: in 2020 - 306 pcs/m2; in 2021 - 408 pcs/m2; in 2022 - 96 pcs/m2. It has been shown that foliar treatment of soybean plants with nutrient deficiency correctors has an impact on nodulation rates, with differences being noted depending on the treatment time. In the variant of Polydon NPK treatment in the primordial leaf phase, the nodulation parameters were minimal in the experiment over the years of the study (86; 216; 56 pcs/m2). Treatment of SK Veda soybean plants in the primordial leaf phase with molybdenum-containing fertilizers ensures the formation of larger nodules. The values of the nodule weight in the flowering phase in the variant of the treatment of Polydon plants with molybdenum in the primordial leaf phase increased by 1.56; 2.09; 1.11 times, respectively, for 2020, 2021, 2022. Nitrogenase activity averaged 26.4-281.6 µg N2/plant.h over the years of the study hour. In the control (inoculation with nitrogen-fixing microorganisms), the activity of nitrogenase was 208.3 µg N2/plant.h. Inoculation of soybean seeds with nitrogen-fixing microorganisms and foliar treatment of plants with Polydon molybdenum increased nitrogenase activity by 35.2-19.1 % and increased protein content by 5.0-3.9 % relative to control, depending on the treatment phase.

Comparative analysis of nitrogen content and its influence on actinorhizal nodule and rhizospheric microorganism diversity in three Alnus species.

Alnus spp. (alder) are typical nonleguminous nitrogen-fixing trees that have a symbiotic relationship with Frankia. To explore the differences in nitrogen-fixing microorganisms between three alders (A. cremastogyne, A. glutinosa, and A. formosana) with different chromosome ploidies, the community structure and compositional diversity of potential nitrogen-fixing microorganism in root nodules and rhizosphere soil were comparatively analyzed using 16S rRNA and nitrogenase (nifH) gene sequencing. The nitrogen contents in the root nodules and rhizosphere soil were also determined. The results showed that the contents of total nitrogen and nitrate nitrogen in the root nodules of the three alders are significantly higher than those in the rhizosphere soils, while the ammonium nitrogen content show the opposite trend. The family, genus, and species levels showed obviously differences between root nodules and rhizosphere soils, while there were no significant differences at the classification level between the three alders. At the phylum level, the dominant phyla from 16S rRNA and nifH gene data in the root nodules and rhizosphere soil of the three alders are phylum Actinomycetota and phylum Pseudomonadota, respectively. The LEfSe results showed that there are significant differences in the dominant groups in the root nodules and rhizosphere oil of the three alders. The relative abundances of dominant groups also showed obvious differences between the root nodules and rhizosphere soils of three alders. The relative abundances of Frankia and unclassified_Frankia in root nodules are obviously higher than those in rhizosphere soils, and their relative abundances in A. glutinosa root nodules are significantly higher than those in A. cremastogyne and A. formosana at the genus and species levels. The diversity of potential nitrogen-fixing microorganism from 16S rRNA and nifH gene data in the A. glutinosa root nodules and rhizosphere soils are all higher than those in A. cremastogyne and A. formosana. The results of functional prediction also showed that the OTUs for nitrogen fixation, nitrate respiration, and ureolysis in A. glutinosa root nodules are higher than those in the other two alders. Redundancy analysis revealed that the total nitrogen content mostly affects the Frankia community. Overall, there are significant differences in the community composition and structure of potential nitrogen-fixing microorganism in the root nodules and rhizosphere soils between the three alders. A. glutinosa showed a relatively stronger nitrogen fixation capacity than A. formosana and A. cremastogyne. The results help elucidates how the community structure and nitrogen-fixing ability of potential nitrogen-fixing microorganism differ between alder species and serve as a reference for applying Frankia to alder plantations.

Leptolyngbya sp. XZMQ and Bacillus XZM co-inoculation reduced sunflower arsenic toxicity by regulating rhizosphere microbial structure and enzyme activity

Microorganisms are of great significance for arsenic (As) toxicity amelioration in plants as soil fertility is directly affected by microbes. In this study, we innovatively explored the effects of indigenous cyanobacteria (Leptolyngbya sp. XZMQ) and plant growth-promoting bacteria (PGPB) (Bacillus XZM) on the growth and As absorption of sunflower plants from As-contaminated soil. Results showed that single inoculation and co-inoculation stimulated the growth of sunflower plants (Helianthus annuus L.), enhanced enzyme activities, and reduced As contents. In comparison to the control group, single innoculation of microalgae and bacteria in the rhizosphere increased extracellular polymeric substances (EPS) by 21.99% and 14.36%, respectively, whereas co-inoculation increased them by 35%. Compared with the non-inoculated group, As concentration in the roots, stems and leaves of sunflower plants decreased by 38%, 70% and 41%, respectively, under co-inoculation conditions. Inoculation of Leptolyngbya sp. XZMQ significantly increased the abundance of nifH in soil, while co-inoculation of cyanobacteria and Bacillus XZM significantly increased the abundance of cbbL, indicating that the coupling of Leptolyngbya sp. XZMQ and Bacillus XZM could stimulate the activity of nitrogen-fixing and carbon-fixing microorganisms and increased soil fertility. Moreover, this co-inoculation increased the enzyme activities (catalase, sucrase, urease) in the rhizosphere soil of sunflower and reduced the toxic effect of As on plant. Among these, the activities of catalase, peroxidase, and superoxide dismutase decreased. Meanwhile, co-inoculation enables cyanobacteria and bacteria to attach and entangle in the root area of the plant and develop as symbiotic association, which reduced As toxicity. Co-inoculation increased the abundance of aioA, arrA, arsC, and arsM genes in soil, especially the abundance of microorganisms with aioA and arsM, which reduced the mobility and bioavailability of As in soil, hence, reduced the absorption of As by plants. This study provides a theoretical basis for soil microbial remediation in mining areas.

Microbiological assessment of the state of urban soils of the oil and gas region on the example of the territory of Kogalym

In the course of this work, the total numbers of heterotrophic microorganisms and the numbers of microbes participating in the nitrogen cycle (ammonifying, denitrifying, nitrifying and nitrogen-fixing ones) in urban and natural (background) soils of Kogalym were estimated. A relation between the obtained results with geochemical indicators was revealed. Our microbiological analysis showed the predominance of nitrogen-fixing microorganisms in urban soils (5.0×104 – 2.0×106 CFU/g of soil), which were on average 44 less than in natural soils. In the last ones the average number of denitrifying microorganisms was 7.0×104 CFU/g of soil, exceeding 1.3 times their number in urban soils. Based on the information obtained, microbial contents in the soils of Kogalym were established as a row: nitrogen fixators > ammonifiers > heterotrophs > denitrifiers; in background samples: denitrifiers > ammonifiers > heterotrophs > nitrogen fixators. According to the data of ecological and geochemical analysis, an excess of the MPC of mobile forms of heavy metals, such as Cu, Ni and Zn, was revealed in the Eastern Industrial zone of the city. A significant inverse correlation was revealed between the number of denitrifying microorganisms in the Kogalym soil microbiocenoses and the content of mobile Ni and Cu forms, which points to a possible negative effect of these metals on the development of denitrifiers. The minimum number of ammonifying, denitrifying and nitrogen-fixing microorganisms was found in the Eastern Industrial zone, especially in the soil samples that were taken near the railway. On the whole, the absence of noticeable differences in the microorganisms` content of the studied groups in urban and natural soils indicates a low level of soil pollution in Kogalym. The obtained results represent the basis for subsequent ecological monitoring of the soils in the city and adjacent oil-producing areas, forecasting the environmental consequences of anthropogenic activities in these territories.

Impact of advanced soil conservation technologies for growing maize on sloping terrains on soil microbiota

Water erosion leads to the loss of soil, nutrients, organic matter, disruption of soil structure, reduction of moisture capacity, loss of biodiversity, and is the most significant soil degradation process when growing agricultural crops on sloping terrain. Soil microorganisms are the basis of the functioning of ecosystems, the circulation of substances, soil-forming processes and the formation of the soil structure. Microbiological indicators, such as numbers, microbial biomass, enzyme activity, etc., are a sensitive indicator of the changes that have occurred in the soil, under the influence of anthropogenic or natural impacts. The present study is on the abundance of major groups of soil microorganisms, when applying different tillage systems in growing maize on sloping terrain. The study was carried out on Carbonate Black Earth, at the Experimental Station for Combating Soil Erosion, at IASSPP “N. Pushkarov”, in the village of Trastenik, Ruse, Agricultural Academy - Sofia. A field experience with corn for grain, applying traditional and anti-erosion technologies (surface and vertical mulching) for growing corn, is presented. The obtained results show a positive influence of the applied soil protection technologies on the number of saprophytic bacteria, mold fungi, actinomycetes, nitrogen-fixing and cellulose-degrading microorganisms.

Harmonized biochemical modification of cell walls to get permission for entrance of Azospirillum sp. to rice roots

Biological nitrogen-fixation is important in increasing crop efficiency. Azospirillum is a nitrogen-fixing microorganism that naturally coexists with grasses roots. The present study was undertaken to clarify the role of rice root cell walls in the acceptance of two Azospirillum species, alone or in combination with indole-3-acetic acid (IAA) and gibberellic acid (GA3) treatments. Rice seedlings were grown in Yoshida solution for 21 days and then inoculated with A. brasilense and A. irakens in the presence of 0, 0.57, and 1.14 mM of IAA or 0, 0.29, and 0.58 mM GA3 or a combination of 1.14 mM of IAA and 0.58 mM of GA3. The results showed that the amount of hydrogen peroxide, lipid peroxidation, total nitrogen and activity of ferulic acid peroxidase, NADPH oxidase, nitrate reductase, pectin methyl esterase, cellulase, mannanase, xylanase and pectinase were significantly increased in inoculated samples treated with or without phytohormones. The highest activity of these enzymes was observed in A. brasilense- inoculated rice roots in auxin+gibberellin treatment. In the latter, the activity of phenylalanine ammonia lyase and wall ferulic acid peroxidase enzymes, the content of cell wall polysaccharide, lignin, and total phenolic compounds were the least, compared to controls and also with those samples which were inoculated with A. irakens. The results indicate an active role of the wall and its enzymes in allowing bacteria to enter the roots. Understanding this mechanism can improve the methods of inoculating bacteria into plants and increase crop efficiency, which will result in reduced use of chemical fertilizers and their destructive environmental effects.

Complete genome sequence of Rhizobium leguminosarum bv. viciae SRDI969, an acid-tolerant, efficient N2-fixing microsymbiont of Vicia faba.

We report the complete genome sequence of Rhizobium leguminosarum bv. viciae SRDI969, an acid-tolerant, efficient nitrogen-fixing microorganism of Vicia faba. The 6.8 Mbp genome consists of a chromosome and four plasmids, with the symbiosis and nitrogen fixation genes encoded on the chromosome.

Intended and unintended impacts of nitrogen-fixing microorganisms and microbial inhibitors on nitrogen losses in contrasting maize cropping systems.

Efforts to mitigate the nitrogen (N) footprint of maize production include using N-fixing microbes (NFM) and/or microbial inhibitors. We quantified the effects of NFM, the nitrification inhibitor (NI) DMPSA, and the urease inhibitor (UI) NBPT, each applied by itself or paired with another additive, on nitrous oxide (N2 O) emissions, nitrate (NO3 - ) leaching, and crop performance in contrasting irrigated and rainfed maize systems over two growing seasons. We also used published emission factors to estimate indirect N2 O emissions from leached NO3 - that can be converted to N2 O. Agronomic effects were relatively small; the NI+NFM treatment increased N use efficiency and grain yield and protein content in some cases by 11-14% relative to a treatment receiving only urea. Most of the additive treatments reduced direct (in-field) N2 O emissions, most consistently for treatments that contained NI which reduced emissions by 24-77%. However, these beneficial effects were counteracted by increased NO3 - leaching, which occurred most consistently with UI or NFM applied as single additives or with NI. In these treatments, NO3 - leaching increased during at least one growing season, and at both sites, by factors of 2 to 7. In three site-years, increased NO3 - leaching with NFM and NI+NFM offset large reductions in direct N2 O, such that total direct + indirect N2 O emissions were not different from that in the urea-only treatment. These unintended effects may have resulted from unfavorable rainfall timing, varying crop N demand, and declining additive effectiveness. Use of these soil additives requires caution and further study. This article is protected by copyright. All rights reserved.

Active Nitrogen Fixation by Iron-Reducing Bacteria in Rice Paddy Soil and Its Further Enhancement by Iron Application

In rice paddy soil, biological nitrogen fixation is important for sustaining soil nitrogen fertility and rice growth. Anaeromyxobacter and Geobacteriaceae, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria dominant in paddy soils. They utilize acetate, a straw-derived major carbon compound in paddy soil, as a carbon and energy source, and ferric iron compounds as electron acceptors for anaerobic respiration. In our previous paddy field experiments, a significant increase in soil nitrogen-fixing activity was observed after the application of iron powder to straw-returned paddy field soil. In addition, combining iron application with 60–80% of the conventional nitrogen fertilizer rate could maintain rice yields similar to those with the conventional nitrogen fertilization rate. It was thus suggested that iron application to paddy soil increased the amount of nitrogen fixed in the soil by enhancing nitrogen fixation by diazotrophic iron-reducing bacteria. The present study was conducted to directly verify this suggestion by 15N-IRMS analysis combined with 15N-DNA-stable isotope probing of iron-applied and no-iron-applied plot soils in an experimental paddy field. In no-iron-applied native paddy soil, atmospheric 15N2 was incorporated into the soil by biological nitrogen fixation, in which diazotrophic iron-reducing bacteria were the most active drivers of nitrogen fixation. In iron-applied paddy soil, the amount of 15N incorporated into the soil was significantly higher due to enhanced biological nitrogen fixation, especially via diazotrophic iron-reducing bacteria, the most active drivers of nitrogen fixation in the soil. Thus, our previous suggestion was verified. This study provided a novel picture of active nitrogen-fixing microorganisms dominated by diazotrophic iron-reducing bacteria in paddy soil, and directly proved the effectiveness of iron application to enhance their nitrogen fixation and increase the incorporation of atmospheric nitrogen into soil. The enhancement of biological nitrogen fixation in paddy fields by iron application may lead to novel and unique paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with reduced nitrogen fertilizer input and lower environmental nitrogen burdens.

The effectiveness of sewage sludge biochar amendment with Boehmeria nivea L. in improving physicochemical properties and rehabilitating microbial communities in mine tailings

Biochar amendment can be adopted to improve soil substrate, in turn facilitated phytoremediation. However, improvements to the properties of tailings following different feedstocks of biochar amendment in phytoremediation, particularly the impacts on nitrogen cycle and the related nitrogen-fixing microorganisms remain unclear. In this study, a 100-day pot experiment was designed to determine the co-effects of different combinations of woody and non-woody biochar, namely hibiscus cannabinus core biochar (HB), sewage sludge biochar (SB), chicken manure biochar (MB) and two crops (Cassia alata L., Boehmeria nivea L.). It was found that, on the one hand, biochar amendment directly immobilized heavy metal (loid) contamination in the tailings; on the other hand, biochar amendment, particularly non-woody SB, improved soil properties (i.e., the combination of SB with crops increased the total nitrogen content by 4.7–7.5 times). This indirectly improved phytostabilization (i.e., SB increased crop height 1.5–1.8 fold, root length 3.3–3.7 fold, decreased NH4NO3-extractable Pb, Cu, Cd and also increased the relative abundance of nitrogen-fixing bacteria such as Mesorhizobium, Bradyrhizobium, and Rhizobium). Besides this, redundant analysis shown that the carbon, nitrogen sources, and pH provided by the biochar were identified as the key factors associated with the nitrogen-fixing bacteria. Through the comprehensive evaluation of different biochar amendment in phytoremediation, it was found that the non-woody SB got higher comprehensive score (3.1–3.6) in biochar amendment in phytoremediation, especially in Boehmeria nivea L. Thus, the combination of non-woody SB and Boehmeria nivea L. improved microbial function, while the microorganisms in turn promoted crop growth. Our results revealed the prospect of using non-woody SB assisted Boehmeria nivea L. for phytoremediation in multi-metal mine tailings.

Comparative characteristics of the microbiological composition of soils of the K.A. Timiryazev Garden of the Lipetsk region

The work is devoted to a comparative analysis of the quantitative and qualitative microbiological composition of soils on the territory of the former Timiryazev gardens in the Dolgorukovsky district of the Lipetsk region. The samples were taken from sites where old apple trees and recultivated soils grow, differing in their properties and composition of microorganisms. The article presents the results of identification of such groups of microorganisms as ammonifying bacteria (total microbial number), microscopic fungi, actinomycetes, nitrogen-fixing microorganisms, cellulolytics.

Successful seed management of perennial legumes as the key to expanding the sowing areas of field and meadow agrophytocoenoses

Purpose. To investigate and theoretically substantiate methods of increasing the sowing and productivity properties of seeds of perennial legumes and, on their basis, develop new and improve existing resource-saving, competitive growing technologies due to the use of mineral, fast-acting limestone fertilizers, seed inoculation with bacterial preparations based on various strains of nitrogen-fixing microorganisms and foliar feeding during the growing season with biostimulants and anti-stressors in order to expand economically valuable field and meadow grass stands on degraded natural pastures. Methods. Field, laboratory, visual, measuring, weight, quantitative, test sheaf method, mathematical, statistical. Results. Agrobiological bases for the formation of fruiting elements of perennial leguminous grasses with high productivity and sowing properties have been developed. They imply seed inoculation with the bacterial preparation Rhizobophyt 0.15 l/ha and foliar fertilizing with anti-stressor in the phase of stemming and budding of grasses on the ground of the basic fertilizer for cover crop (N30P60-90K60-90) in combination with a fast-acting limestone fertilizer (Ca(OH)2 – slaked lime – 1.2 t/ha) 0.5 norms for hydrolytic acidity. This contributed to the formation of the maximum seed yield of alfalfa – 0.29-0.30 t/ha, meadow clover – 0.47-0.49 t/ha, hybrid clover – 0.30-0.31 t/ha, deer vetch – 0.45-0.47 t/ha. Conclusions. For the successful seed production of new high-yielding varieties of perennial leguminous grasses with high sowing and productive properties, a mandatory measure is, against the background of the main fertilization with mineral and fast-acting limestone fertilizers for cover crops, the pre-sowing treatment of seeds with the bacterial preparation Rhizobophyt and foliar fertilizing with the anti-stressor Agrohumat, which contributed on average, over the years of research, to increase seed productivity by 21-57%.

Isolation and Characterization of Thermotolerant Mungbean (Vigna Radiata L.) Rhizobial Isolate As Biofertilizer

Rhizobia act as primary nitrogen fixing microorganisms in the root of leguminous plants. Efficient rhizobia are helpful in increasing productivity of legumes. In the present investigation a total of twenty rhizobial isolates were retrieved from root nodules of mungbean plants growing in field during summer season. On evaluation of plant growth promoting traits of all rhizobial isolates it was found that rhizobial isolate HSR1 had maximum indole acetic acid (IAA) production (58.83 μg/ml), ammonia excretion (4.78 μg/ml) and phosphate solubilization potential. Other plant growth promoting traits like aminocyclopropane- 1-carboxylic acid (ACC) deaminase activity, siderophore production and hydrogen cyanide (HCN) production were also exhibited by isolate HSR1. This isolate was able to survive 45ºC and exhibited plant growth promoting traits at high temperature. Genomic DNA extracted from isolate HSR1 was subjected to amplification of 16S rRNA gene for identification. The similarity searching of the sequence obtained after 16S rRNA gene sequencing showed 99% similarity with Sinorhizobium sp. T25, which was confirmed by morphological and biochemical tests. Presence of good plant growth promoting traits makes HSR1 a promising strain to be developed as biofertilizer to improve soil fertility and plant growth. Bangladesh J. Bot. 52(2): 217-224, 2023 (June)

New perspectives for bio-technical treatment of oxalate-containing waste streams from bauxite processing

Alumina is typically produced from bauxite ore using the Bayer process, in which the ore is mixed with alkaline liquor under elevated temperatures. Australian bauxite ore contains a wide range of organics, which detrimentally affect the Bayer process. Therefore, the removal of organic compounds from the alkaline Bayer process liquor is critical in maintaining process efficiency and alumina quality. Oxalate (C2O42−) is a key organic impurity in the Bayer process liquors that requires removal as it increases in concentration in the processing circuit as the Bayer liquor is continually recycled. Compared to conventional physiochemical or physical methods (e.g., chemical precipitation, wet-oxidation, liquor burning), microbial bioreactor treatment processes have the potential to be more economical and environmentally sustainable for oxalate removal. Some Australian alumina refineries have implemented full-scale bioreactors such as moving bed biofilm reactors (MBBRs) and aerobic suspended growth bioreactors (ASGB). While these bioreactors are robust and effective in removing oxalate, they have some limitations, such as the need for pre-acidification of influent and the loss of ammonia (nutrient) through volatilization. Therefore, this study aimed to provide an overview of the fundamentals and recent advances in biotechnical processes for the treatment of alkaline oxalate-containing liquor. Laboratory-scale studies on promising new biotreatment concepts, such as the use of bioelectrochemical systems to facilitate concurrent oxalate degradation and caustics recovery, as well as the utilization of nitrogen-fixing microorganisms to obviate the requirement for external nutrient dosage, are discussed. Perspectives for further research on oxalate-containing waste streams are also proposed.

Ivy Geranium (Pelargonium peltatum (L.) L’Hér.) Plant Growth and Flowering as Affected by Mineral or Biofertilizer with or without Compost Amendment

Sustainable agriculture aims to eliminate the excessive usage of chemical fertilizers and can be crucial for soil fertility. A factorial pot experiment in a randomized complete block design was carried out in King Khaled International Airport Nursery, Riyadh, Saudi Arabia, during 2019/2020, to evaluate the role of a biofertilizer (i.e., Bio-Fert, nitrogen-fixing microorganisms; Biot-Phos, phosphorus-released microorganism; and Bio-Potas, potassium-released microorganisms, either alone or in combinations) and slow-release compound chemical fertilizer (Osmocote), with or without compost, on Pelargonium peltatum plant growth, flowering, chlorophyll level, and ion percentage. Soil amendment with compost in general significantly increased plant growth and flowering attributes as well as chlorophyll level, nitrogen (N), phosphorous (P), and potassium (K) percentage over garden soil (without compost). All growth and flowering traits as well as ion percentage and chlorophyll level were significantly increased by biofertilizer treatments either alone or in combinations. The supreme treatment was the triple interaction over single or double interactions or untreated plants. Osmocote application increases chlorophyll levels, ions, flowering, and vegetative growth relative to untreated plants. Additionally, the data also revealed that all interactions between either osmocote or biofertilizers with compost significantly increased all studied attributes over each treatment alone or untreated control plants. Accordingly, it is recommended to add compost to the soil along with a triple mixture of biofertilizers for obtaining high plant growth and flowering attributes along with soil fertility.

Biodiversity of microbial populations as the indicator of biogenicity of soil under ashes and agricultural soil

The number, activity and diversity of microorganisms define the level of biogenicity and indicate the quality and health of the soil. The abundance and structure of microbial communities vary in different types of soils, so in order to preserve and protect natural and agroecological systems, in addition to physical-chemical analyses, monitoring of dynamics of microbiological activity in agricultural and non-agricultural soil is also necessary. Each type of soil has its own characteristic micro biocenosis, and different methods of soil use can have a positive or negative impact on microbiological activity, which directly affects the fertility of the soil. Soil bacteria are very important in biogeochemical cycles, and biological nitrogen fixation plays an important role in nitrogen cycling by transferring atmospheric dinitrogen into the soil. It is performed by symbiotic and asymbiotic nitrogen-fixing microorganisms, called nitrogen fixators. Amonificators are bacteria that play a very important role in soil ecosystem, as well as nitrogen fixators. This group of bacteria participates in the processes of protein decomposition and transformation. The aim of the paper is to indicate, based on the presence of nitrogen fixators and amonificators in soil under ashes, the biogenicity of this soil at four different localities: pure ashes, soil under ashes covered with herbaceous vegetation, soil under ashes covered with wood vegetation and agricultural soil, and to give advice on future activities regarding recultivation of these types of soil under ashes. The results of the research showed that microorganisms are mostly represented in different numbers in the tested soils, which indicates variations on the soil biogenicity and quality.

Realization of Nodulation and Nitrogen-Fixing Activities of Bradyrhizobium japonicum and Rhizosphere Microbiota through Seed Treatment with Pesticide Standak Top and Spraying Plants with Soybean Seed Lectin

The idea of the study was to use soybean lectin as a biologically active compound with a broad spectrum of action to spray soybean plants for stabilization of the formation and functioning of the soybean-rhizobium symbiosis as well as the nitrogen-fixing activity of rhizosphere microbiota against the background of seed treatment with chemical plant protection product Standak Top — an innovative pesticide with fungicidal and insecticidal activity for the control of major diseases and pests of soybean plants. Aim. To study the peculiarities of formation and functioning of soybean-rhizobium symbiosis as well as the nitrogen-fixing activity of rhizosphere microbiota under spraying plants with specific soybean seed lectin on the background of seed treatment with Standak Top and inoculation with nodule bacteria Bradyrhizobium japonicum 634b on the sowing day in the conditions of pot experiments with soil as a substrate. Methods. Physiological, microbiological, gas chromatography, and statistical methods were used. Results. It was shown that after seed treatment with Standak Top (1.5 L/ton of seeds) on the sowing day, there was observed suppression of the process of nodule formation on the roots in the period of soybean vegetative growth. The nitrogen-fixing activity of the symbiotic system was at the control level, while the functional activity of soil diazotrophs was suppressed (by 1.2—2.2 times). Spraying plants in the phase of two trifoliate leaves (V2) with soybean seed lectin (without pesticide) led to an increase in the total mass of nodules on the plant (by 1.5 and 1.9 times as well as by 2.3 and 2.0 times compared to the control of inoculation in the phase of three trifoliate leaves (V3) and beginning of pod formation (R3), respectively). The increase in the total mass of the symbiotic apparatus on soybean roots in the phases V3 and R3 respectively was by 1.4 and 1.5 times in comparison with seed treatment with Standak Top, and the mass of one nodule was higher by 1.3 and 1.6 times, respectively. Soybean seed lectin led to a signifi cant increase in the actual nitrogenase activity of the soybean-rhizobium symbiosis. It was 2.9 and 1.9 times higher compared to control of inoculation and 2.1 and 1.8 times compared to the variant of inoculation + pesticide in the V3 and R3 phases, respectively. The functional activity of soil nitrogen-fixing microorganisms did not change significantly. The use of soybean seed lectin against the background of the seed treatment with Standak Top and inoculation contributed to the stabilization and increase in the rhizobia nodulation ability, the suppression of which was due to the infl uence of such an anthropogenic factor as pesticides. Th ere was observed an increase in the number (by 1.6 and 1.2 times) and mass of root nodules (by 2.2 and 1.5 times and 1.4 and 1.2 times, respectively, compared to the controls of inoculation and inoculation + pesticide). Soybean seed lectin significantly increased the nitrogenase activity of the symbiosis against the background of Standak Top (by 1.9 and 1.6 times and 1.4 and 1.5 times, respectively, in the V3 and R3 phases of soybean ontogenesis) compared to the control of inoculation and inoculation + Standak Top. Conclusions. The obtained results suggest the possibility of using the method of spraying plants with specific lectin as a means of leveling (or mitigating) the negative effect of pesticides used for the seed treatment on the formation and functioning of the symbiosis and rhizosphere diazotrophic microbiota. This indicates the prospects of studying the biological activity of phytolectins in spraying plants in order to regulate the formation and functioning of phytobacterial systems, as well as their responses to various environmental or anthropogenic stress factors, in particular, to the effect of chemical plant-protecting products used for the seed treatment.

Influence of Methyl Jasmonate and Salicylic Acid as Components of the Cultivation Medium for Rhizobium on Formation of Different-Efficiency Symbiotic Systems Glycine max — Bradyrhizobium japonicum

Phytohormones are important in the main pathways of transduction of symbiotic signals between macro- and microsymbionts, and understanding of their participation in integration with other metabolic pathways, including prooxidant-antioxidant systems, is crucial in the formation of different-efficiency symbiotic systems. Aim. To investigate the effect of salicylic acid (SA, 50 μM) and methyl jasmonate (MJ, 0.75 μM) as components of the cultivation media of different in the activity and virulence rhizobia 604k and B1-20 on the peculiarities of the formation of symbiotic systems in terms of intensity and activity of catalase, as well as on the course of nodulation and nitrogen fixation. Methods. Microbiological (cultivation of nitrogen-fixing microorganisms, seed inoculation), physiological (vegetation experiment), biochemical (spectrophotometry, gas chromatography), and statistical. Results. It was found that the use of SA (50 μM) as an additional component of the culture medium of active rhizobia Tn5-mutant B1-20 for seed inoculation induces increased levels of peroxide production and catalase activity in soybean roots in the early stages of symbiosis, which contributes to the effectiveness of its symbiotic apparatus. Addition of MJ (0.75 μM) to the culture medium of rhizobia B1-20 does not affect changes in peroxide content and catalase activity in the roots, however, stimulates the processes of nodulation and reduces nitrogen fixation. It has been shown that modification of the cultivation medium of inactive rhizobia of the highly virulent strain 604k using SA (50 μM) or MJ (0.75 μM) does not change the peroxide content and leads to an increase in catalase activity in soybean roots during the formation of an ineffective symbiotic system with activation of nodulation processes. Conclusions. When using SA (50 μM) or MJ (0.75 μM) as components of the culture medium for rhizobia of different activity and virulence (604k and B1-20), differences were recorded in the levels of functioning of pro-antioxidant systems, in particular, in the production of peroxides and active catalase complexes, at the early stages of the formation of symbiotic systems of Glycine max — Bradyrhizobium japonicum, which affects the intensity of the processes of nodulation and nitrogen fixation.

Marine nitrogen fixation as a possible source of atmospheric water-soluble organic nitrogen aerosols in the subtropical North Pacific

Abstract. Water-soluble organic nitrogen (WSON) in marine atmospheric aerosols affect the water solubility, acidity, and light-absorbing properties of aerosol particles, which are important parameters in assessing both the climate impact and the biogeochemical cycling of bioelements. Size-segregated aerosol and surface seawater (SSW) samples were simultaneously collected over the subtropical North Pacific to investigate the origin of WSON in the marine atmosphere. The fine-mode WSON concentration (7.5 ± 6.6 ngN m−3) at 200–240∘ E along 23∘ N, defined as the eastern North Pacific (ENP), was significantly higher than that (2.4 ± 1.9 ngN m−3) at 135–200∘ E, defined as the western North Pacific (WNP). Analysis of the stable carbon isotope ratio of water-soluble organic carbon (WSOC; δ13CWSOC) together with backward trajectory indicated that most of the observed WSON in the fine particles in the ENP originated from the ocean surface. We found positive relations among nitrogen-fixation rate, dissolved organic nitrogen (DON) in SSW, and the WSON concentrations. The result suggests that reactive nitrogen (DON and ammonium), produced and exuded by nitrogen-fixing microorganisms in SSW, contributed to the formation of WSON aerosols. This study provides new insights into the role of ocean-derived reactive nitrogen aerosols associated with marine microbial activity.