Promote Nitrogen Fixation Research Articles

Foliar application of iron strengthened- artificial humic acid promotes nitrogen fixation and improves soybean yield

Foliar application of iron strengthened- artificial humic acid promotes nitrogen fixation and improves soybean yield

Composting and Liquid Formulations: Panacea to Better Yield in Agriculture: A Review

Liquid formulations, including aqueous, oil, and polymer-based products, often use polysaccharides to alter fluid properties. Liquid inoculants offer cost-effective alternatives to solid carriers, particularly benefiting small producers in India by overcoming transportation and processing challenges. Ideal liquid inoculants are non-toxic, low-cost, uniform, nutrient-supplemented, and support rapid microorganism release and growth. Effective formulations stabilize organisms, ensure easy field delivery, protect against environmental factors, and enhance microbial activity. Rich in nutrients and organic matter, compost enhances the texture, structure, and moisture retention of soil, improving soil qualities and crop productivity. It boosts soil enzyme activity and microbial populations, promoting nitrogen fixation and nutrient availability. Organic manure applications increase soil fertility, water retention, and reduce bulk density. Field and horticultural crops, such as potatoes, chillies, and tomatoes, show significant yield improvements with compost, which also suppresses plant diseases and weed populations. These findings underscore the importance of adopting liquid formulations and composting as sustainable agricultural practices.

PROTECTION OF SOYBEAN AGAINST MAIN DISEASES

An analysis of the most common diseases of soybeans in the forest-steppe of Ukraine was carried out. It was determined that the most common diseases were alternaria, powdery mildew, fusarium wilt, septoriosis, white rot, bacterial burns, etc. The species composition of diseases and the degree of their development were largely influenced by the weather conditions of the growing period. The reasons for the decrease in plant productivity and the decrease in the productivity of soybean seeds have been established. It was noted that an important point in the soybean protection system is the time of treatments. When determining the treatment time, you should first of all focus on the growth phase of the plant, and only then on the spread, presence or absence of the disease. The effectiveness of the use of fungicides in soybean agrocenosis is justified. The main active substances that are effective and control the phytosanitary condition of soybean crops for certain types of diseases are considered. A comprehensive and effective solution for the protection of soybean crops was found, namely Vibrance® RFC and Merivon® Pro poisons. Vibrance® RFC - its chemical composition contains fludioxonil 25 g/l, metalaxyl M 37 g/l and sedaxan™ 50 g/l. The increased rate of metalaxyl M improves the effectiveness of the product in the fight against systemic infections, namely ascochitosis, peronosprosis, pythiosis; fludioxonil provides reliable control against Fusarium spp (F. graminearum) and enhances control against Ascochyta spp. Sclerotinia sclerotiorum, Cercospora spp., Colletotrichum spp., Penicillium spp., Aspergillus niger, Phomopsis spp.; Sedaxan™ is an active ingredient that is simply essential for soybean seeds, as it is quite effective in protecting against Sclerotinia sclerotiorum, Cercospora spp., Colletotrichum spp, Phomopsis spp., which caused significant damage to crops in 2022. Additional adjuvants in the composition, which are components of Formula M®, increase efficiency by maximally uniform application and reliable retention of the drug on the seed. Merivon® Pro is designed to control root rot (fusarium, rhizoctoniosis, pythiosis), anthracnose, peronosporosis, ascochitosis, phomopsis, seed mold. The drug combines fluxapiroxad, which has unique mobility and effective action, and pyraclostrobin, which prevents the growth of fungal mycelium and suppresses the respiration of the pathogen. The results on experimental plots with a high background of fusarium and rhizoctoniosis show that when applying the registered rate of the poison, an increase of 0.33 t/ha can be obtained. This is almost 20% more than the control plots. In addition, the special formulation of these products is designed for safe simultaneous application together with nitrogen-fixing bacteria. This ensures that farmers can continue to use them to promote nitrogen fixation, a key factor in crop growth, while protecting the seed from disease.

Degradation of Complex Carbon Sources in Organic Fertilizers Facilitates Nitrogen Fixation.

Biological nitrogen fixation is crucial for agriculture and improving fertilizer efficiency, but organic fertilizers in enhancing this process remain debated. Here, we investigate the impact of organic fertilizers on biological nitrogen fixation through experiments and propose a new model where bacterial interactions with complex carbon sources enhance nitrogen fixation. Field experiments showed that adding organic fertilizers increased the nitrogenase activity by 57.85%. Subculture experiments revealed that organic fertilizer addition enriched genes corresponding to complex carbon and energy metabolism, as well as nifJ involved in electron transfer for nitrogenase. It also enhanced bacterial interactions and enhanced connectors associated with complex carbon degradation. Validation experiments demonstrated that combinations increased nitrogenase activity by 2.98 times compared to the single. Our findings suggest that organic fertilizers promoted nitrogen fixation by enhancing microbial cooperation, improved the degradation of complex carbon sources, and thereby provided utilizable carbon sources, energy, and electrons to N-fixers, thus increasing nitrogenase activity and nitrogen fixation.

Enhancing iron content and growth of cucumber seedlings with MgFe-LDHs under low-temperature stress.

The development of cost-effective and eco-friendly fertilizers is crucial for enhancing iron (Fe) uptake in crops and can help alleviate dietary Fe deficiencies, especially in populations with limited access to meat. This study focused on the application of MgFe-layered double hydroxide nanoparticles (MgFe-LDHs) as a potential solution. We successfully synthesized and characterized MgFe-LDHs and observed that 1-10mg/L MgFe-LDHs improved cucumber seed germination and water uptake. Notably, the application of 10mg/L MgFe-LDHs to roots significantly increased the seedling emergence rate and growth under low-temperature stress. The application of 10mg/L MgFe-LDHs during sowing increased the root length, lateral root number, root fresh weight, aboveground fresh weight, and hypocotyl length under low-temperature stress. A comprehensive analysis integrating plant physiology, nutrition, and transcriptomics suggested that MgFe-LDHs improve cold tolerance by upregulating SA to stimulate CsFAD3 expression, elevating GA3 levels for enhanced nitrogen metabolism and protein synthesis, and reducing levels of ABA and JA to support seedling emergence rate and growth, along with increasing the expression and activity of peroxidase genes. SEM and FTIR further confirmed the adsorption of MgFe-LDHs onto the root hairs in the mature zone of the root apex. Remarkably, MgFe-LDHs application led to a 46% increase (p < 0.05) in the Fe content within cucumber seedlings, a phenomenon not observed with comparable iron salt solutions, suggesting that the nanocrystalline nature of MgFe-LDHs enhances their absorption efficiency in plants. Additionally, MgFe-LDHs significantly increased the nitrogen (N) content of the seedlings by 12% (p < 0.05), promoting nitrogen fixation in the cucumber seedlings. These results pave the way for the development and use of LDH-based Fe fertilizers.

OsCIPK2 mediated rice root microorganisms and metabolites to improve plant nitrogen uptake

Crop roots are colonized by large numbers of microorganisms, collectively known as the root-microbiome, which modulate plant growth, development and contribute to elemental nutrient uptake. In conditions of nitrogen limitation, the over-expressed Calcineurin B-like interacting protein kinase 2 (OsCIPK2) gene with root-specific promoter (RC) has been shown to enhance growth and nitrogen uptake in rice. Analysis of root-associated bacteria through high-throughput sequencing revealed that OsCIPK2 has a significant impact on the diversity of the root microbial community under low nitrogen stress. The quantification of nifH gene expression demonstrated a significant enhancement in nitrogen-fixing capabilities in the roots of RC transgenetic rice. Synthetic microbial communities (SynCom) consisting of six nitrogen-fixing bacterial strains were observed to be enriched in the roots of RC, leading to a substantial improvement in rice growth and nitrogen uptake in nitrogen-deficient soils. Forty and twenty-three metabolites exhibiting differential abundance were identified in the roots and rhizosphere soils of RC transgenic rice compared to wild-type (WT) rice. These findings suggest that OSCIPK2 plays a role in restructuring the microbial community in the roots through the regulation of metabolite synthesis and secretion. Further experiments involving the exogenous addition of citric acid revealed that an optimal concentration of this compound facilitated the growth of nitrogen-fixing bacteria and substantially augmented their population in the soil, highlighting the importance of citric acid in promoting nitrogen fixation under conditions of low nitrogen availability. These findings suggest that OsCIPK2 plays a role in enhancing nitrogen uptake by rice plants from the soil by influencing the assembly of root microbial communities, thereby offering valuable insights for enhancing nitrogen utilization in rice cultivation.

Legume rhizodeposition promotes nitrogen fixation by soil microbiota under crop diversification

Biological nitrogen fixation by free-living bacteria and rhizobial symbiosis with legumes plays a key role in sustainable crop production. Here, we study how different crop combinations influence the interaction between peanut plants and their rhizosphere microbiota via metabolite deposition and functional responses of free-living and symbiotic nitrogen-fixing bacteria. Based on a long-term (8 year) diversified cropping field experiment, we find that peanut co-cultured with maize and oilseed rape lead to specific changes in peanut rhizosphere metabolite profiles and bacterial functions and nodulation. Flavonoids and coumarins accumulate due to the activation of phenylpropanoid biosynthesis pathways in peanuts. These changes enhance the growth and nitrogen fixation activity of free-living bacterial isolates, and root nodulation by symbiotic Bradyrhizobium isolates. Peanut plant root metabolites interact with Bradyrhizobium isolates contributing to initiate nodulation. Our findings demonstrate that tailored intercropping could be used to improve soil nitrogen availability through changes in the rhizosphere microbiome and its functions.

Deciphering Microbial Community and Nitrogen Fixation in the Legume Rhizosphere.

Nitrogen is the most limiting factor in crop production. Legumes establish a symbiotic relationship with rhizobia and enhance nitrogen fixation. We analyzed 1,624 rhizosphere 16S rRNA gene samples and 113 rhizosphere metagenomic samples from three typical legumes and three non-legumes. The rhizosphere microbial community of the legumes had low diversity and was enriched with nitrogen-cycling bacteria (Sphingomonadaceae, Xanthobacteraceae, Rhizobiaceae, and Bacillaceae). Furthermore, the rhizosphere microbiota of legumes exhibited a high abundance of nitrogen-fixing genes, reflecting a stronger nitrogen-fixing potential, and Streptomycetaceae and Nocardioidaceae were the predominant nitrogen-fixing bacteria. We also identified helper bacteria and confirmed through metadata analysis and a pot experiment that the synthesis of riboflavin by helper bacteria is the key factor in promoting nitrogen fixation. Our study emphasizes that the construction of synthetic communities of nitrogen-fixing bacteria and helper bacteria is crucial for the development of efficient nitrogen-fixing microbial fertilizers.

Nitrogen retention driven by cooperative succession of bacterial communities through promoting nitrogen fixation and inhibiting denitrification during straw composting with amino acids addition

Composting is a biological aerobic fermentation process that decomposes organic solid waste and converts it into humus. However, in the process of mineralization or humification of organic matter, a large amount of nitrogen will be lost. Therefore, it is very essential to find strategies to increase nitrogen retention during composting. This study elucidated the biological mechanism underlying the promotion of nitrogen retention during straw composting through the addition of leucine (TL) and phenylalanine (TP). The results indicated that the total nitrogen (TN) content of TL and TP composting final products were 92.97% and 103.90% higher than that of the initial composting, respectively, and 92.68% and 92.58% higher than CK (no amino acids addition) control group. This was due to the succession of bacterial community structure, from a low-modularity relationship with a small amount of high aggregation to a large number of high modular cooperation. This evolution of bacterial community complexity and stability played an important role in nitrogen transformation. The increase of keystones in TL and TP regulated the change of bacterial community function. The change of this interaction made the nitrogen-fixing gene (nifH) abundance and nitrogen-fixing effect significantly improve and inhibits denitrification in high temperature. The negative growth of nitrogen loss rate also confirmed the key role of nitrogen-fixing bacteria. Therefore, amino acids addition played a positive role in improving the nitrogen retention of straw composting.

Effects of Soil Rhizobia Abundance on Interactions between a Vector, Pathogen, and Legume Plant Host.

Soil rhizobia promote nitrogen fixation in legume hosts, maximizing their tolerance to different biotic stressors, plant biomass, crop growth, and yield. While the presence of soil rhizobia is considered beneficial for plants, few studies have assessed whether variation in rhizobia abundance affects the tolerance of legumes to stressors. To address this, we assessed the effects of variable soil rhizobia inoculum concentrations on interactions between a legume host (Pisum sativum), a vector insect (Acyrthosiphon pisum), and a virus (Pea enation mosaic virus, PEMV). We showed that increased rhizobia abundance reduces the inhibitory effects of PEMV on the nodule formation and root growth in 2-week-old plants. However, these trends were reversed in 4-week-old plants. Rhizobia abundance did not affect shoot growth or virus prevalence in 2- or 4-week-old plants. Our results show that rhizobia abundance may indirectly affect legume tolerance to a virus, but effects varied based on plant age. To assess the mechanisms that mediated interactions between rhizobia, plants, aphids, and PEMV, we measured the relative expression of gene transcripts related to plant defense signaling. Rhizobia concentrations did not strongly affect the expression of defense genes associated with phytohormone signaling. Our study shows that an abundance of soil rhizobia may impact a plant's ability to tolerate stressors such as vector-borne pathogens, as well as aid in developing sustainable pest and pathogen management systems for legume crops. More broadly, understanding how variable rhizobia concentrations can optimize legume-rhizobia symbiosis may enhance the productivity of legume crops.

More electrons on Fe and FeN2 promote nitrogen fixation efficiency

The more electrons there are on Fe and FeN2, the faster the electrons transfer to the adsorbed nitrogen gas.

Disparities and mechanisms of carbon and nitrogen conversion during food waste composting with different bulking agents

The low C/N ratio, high moisture content, and low porosity of food waste require the addition of bulking agents for adjustment during the composting process. However, the effect and mechanism of different bulking agents on the reduction of carbon and nitrogen losses are unclear. Therefore, this study conducted experiments to evaluate and clarify the differences in carbon and nitrogen transformation between sawdust, rice husk and wheat bran in food waste composting. The results showed that the addition of bulking agents promoted the conversion of carbon and nitrogen into total organic carbon (TOC) and total organic nitrogen (TON) rather than CO2 and NH3. The carbon and nitrogen losses were reduced by 16.00–25.71% and 11.56–29.54%, respectively. Notably, the Sawdust group exhibited the highest carbon retention, whereas the Wheat_bran group demonstrated superior nitrogen retention. The succession of bacterial communities showed that sawdust enhanced the cellulolysis and xylanolysis functions while wheat bran promoted nitrogen fixation. Correlation analysis was further employed to speculate on potential interactions among carbon and nitrogen components. The incorporation of sawdust and rice husk improved humification partly due to the addition of lignocellulose and the accumulation of total dissolved nitrogen (DTN) in the substrate, respectively. In the process of ammonia assimilation, the addition of wheat bran promoted the accumulation of dissolved organic carbon (DOC), contributing to the synthesis of TON to a degree. These findings offer cost-effective strategies for conserving carbon and nitrogen from loss in food waste composting by selecting suitable bulking agents, ultimately producing high-quality fertilizer.

Integrating Native Plant Mixtures and Arbuscular Mycorrhizal Fungi Inoculation Increases the Productivity of Degraded Grassland

Intense human activities break the grassland–livestock balance and accelerate grassland degradation. We evaluated the use of native dominant species combined with arbuscular mycorrhizal fungi (AMF) in order to recover grassland and restrain grassland degradation. We conducted a full factorial greenhouse experiment to evaluate the interaction effects of native species of distinct traits grass Lolium perenne (L) and legume Trifolium repens (T) with arbuscular mycorrhizal fungi (AMF) inoculation on grass productivity and soil properties across non-degraded, lightly degraded, and severely degraded soils. The grass–legume mixture was manipulated with five ratios (T:L = 1:0, T:L = 1:1, T:L = 3:1, T:L = 1:3, T:L = 0:1). The results showed that L. perenne significantly increased grassland productivity at different grass–legume ratios, regardless of AMF presence or absence. AMF inoculation increased plant N and P content uptake and improved the productivity of degraded grasslands, especially in severely degraded grasslands. The NO3−-N and available P concentrations increased in soil when the legume component increased from T:L = 0:1 (grass monoculture) to T:L = 1:0 (legume monoculture). This may be because the presence of Lolium perenne (L) can promote nitrogen fixation in legumes. Structural equation modeling indicated that grass–legume mixtures directly affected plant biomass, whereas AMF affected plant biomass via providing plant nutrients. A soil quality index based on minimum datasets indicated a significant positive effect of artificial grassland establishment on soil quality. We conclude that planting T:L = 0:1 and T:L = 1:3 combined with AMF inoculation can be used to recover degraded grassland production, and planting T:L = 1:1 and T:L = 1:3 plus AMF inoculation can be applied for grassland nutrient accumulation and stability maintenance.

New insights into the effects of chlorpyrifos on soil microbes: Carbon and nitrogen cycle related microbes in wheat/maize rotation agricultural field

Chlorpyrifos, a broad−spectrum organophosphorus insecticide, has been widely detected worldwide and is a potential neurotoxin and endocrine disruptor. Besides, chlorpyrifos has been proven that have a negative effect on soil microbes. In the present study, chlorpyrifos formulation (LORSBAN®, 45% emulsifiable concentrate) was applied in an agricultural field at the recommended dose (R dose, 270.0 and 337.5 g a.i. ha−1 for wheat and maize respectively) and double recommended (DR) dose. Chlorpyrifos residue level and effect on soil microbes related to soil carbon and nitrogen cycle function were analyzed. Results showed that the half−lives of chlorpyrifos in wheat and maize field soil were 7.23–8.23 and 1.45–1.77 d, respectively. Application of chlorpyrifos at even DR dose did not result in unacceptable residual chlorpyrifos, where the final residual chlorpyrifos in wheat/maize (leaf, stem, and grain) was meet the requirement of the maximum residual limit (0.5 mg kg−1 for wheat and 0.05 mg kg−1 for maize) in China. Chlorpyrifos enhanced the activity of β−glucosidase by increasing the relative abundance of Sphingosinicella and promoted the carbon cycle in wheat field. The changes of cbbLR and cbbLG gene abundance also confirmed that chlorpyrifos could affect the import and export of soil carbon pool. The effect of chlorpyrifos on soil N cycle was determined by changes in the abundance of the bacterial genus Gemmatimonas, which is associated with denitrification. Further analysis of N−cycle functional genes and urease activity showed that chlorpyrifos inhibited nitrogen fixation in wheat field, but promoted nitrogen fixation in maize field. In general, bacterial abundance, urease, and AOA−amoA gene could be early warning markers of chlorpyrifos contamination. The results demonstrated the negative effects of chlorpyrifos on soil microbes especially on soil C and N cycle in actual agricultural field. It provides new insights about chlorpyrifos environmental pollution and its effect on soil ecosystems.

Doping induced asymmetry adjacent structure in h-VN nanoribbon for the promotion of N2 fixation

Vanadium nitride (VN)-based materials have attracted increasing attention in the field of electrochemical catalysis due to their unique structure and inherent electronic properties. However, the nitrogen reduction reaction (NRR) performances of such nitrogen-containing catalysts render very low catalytic activities, and it is a challenge to achieve optimal efficiency. In this work, we propose a strategy for doping hetero-metal atoms to promote nitrogen fixation on vanadium nitrides by using density functional theory (DFT) calculations. We evaluated and compared the activity and selectivity of NRR on in-plane sites as well as on edge sites. We found that the first half of the elements showed high doping rates. Moreover, the NRR catalytic performance of VN can be boosted by a specific metal atom doping strategy, which significantly promotes the N2 adsorption as well as both the activity and selectivity. Finally, the heterogeneous atom pair (HTAP) VMo@edge and VTi@in-plane/edge were selected as the most potential candidates that exhibit the rate-determining step as low as ∼0.2 and ∼0.6 eV, respectively. Our work provides not only a fundamental understanding of the NRR mechanism on VN-based materials, but also a powerful strategy for designing efficient bimetallic NRR electrocatalysts.

Single-layer MoS2 with adjacent Mo sites for efficient electrocatalytic nitrogen fixation via spin-delocalized electrons effect

Electrocatalytic nitrogen fixation is crucial for sustainable NH3 production, however it still suffers from sluggish kinetics. Here, we report that single-layer MoS2 with adjacent Mo sites (A-Mo-MoS2) prepared by preciously controlling the oriented topological conversion could exhibit an exceptional NH3 yield rate of 48.8 µg h–1 mg–1 and Faradic efficiency (FE) of 27.3 % at −0.20 V vs. RHE, far beyond MoS2 with isolated sulfur vacancies (I-SV-MoS2) with a 18.8 µg h–1 mg–1 rate and 8.4 % FE. Theoretical analysis reveal that A-Mo-MoS2 could induce their unpaired spin-polarized electrons to share along the outermost Mo edge, thereby forming a grand spin-delocalized electrons reservoir. Compared to limited spin-localized electrons on I-SV-MoS2, these spin-delocalized electrons could significantly facilitate nitrogen activation and switched the rate-determining step from energy-demanding *N2 hydrogenation to surmountable *HNNH hydrogenation. Our work offers a new strategy to promote nitrogen fixation by spin-delocalized electrons effect.

Genetic variation in GmCRP contributes to nodulation in soybean (Glycine max Merr.)

Symbiosis between soybean and rhizobia contributes to soybean yield and quality. Although secreted rhizobial type III effectors are known to regulate infection and promote nitrogen fixation, much about them remains unknown. Mutation of NopC, a type III effector from Sinorhizobium fredii HH103, reduced nodule numbers and dry weights in 310 soybean accessions, and expression of NopC in soybean hairy roots promoted symbiosis. Based on observed differences in nodule traits between Suinong 14 and Zyd 00,006 inoculated with HH103 and the NopC mutant, 11 QTL associated with rhizobia were identified in chromosome segment substitution lines (CSSLs) derived from Suinong 14 and Zyd 00006. Using chromosome fragment insertion, whole-genome sequencing of Suinong 14 and Zyd 00006, and qRT-PCR, Glyma.19G176300 (GmCRP) was identified as a candidate gene associated with NopC, and GmCRP was found to be induced by NopC to positively regulate nodulation. SNPs located in the regulatory regions of GmCRP influenced its expression response to NopC, with SNPs contributing to nodulation having been selected during domestication. Our findings reveal the function of a soybean gene encoding a rhizobial type III effector that contributes to symbiosis, and will facilitate the practical application of symbiotic nitrogen fixation in molecular breeding.

Efficient sunlight promoted nitrogen fixation from air under room temperature and ambient pressure via Ti/Mo composites

Photocatalytic nitrogen fixation is an important pathway for carbon neutralization and sustainable development. Inspired by nitrogenase, the participation of molybdenum can effectively activate nitrogen. A novel Ti/Mo composites photocatalyst is designed by sintering the molybdenum acetylacetonate precursor with TiO2. The special carbon-coated hexagonal photocatalyst is obtained which photocatalytic nitrogen fixation performance is enhanced 16 times compared to pure TiO2 at room temperature and ambient pressure. The abundant surface defects in this composite were confirmed to be the key factor for nitrogen fixation. The 15N2 isotope labeling experiment was used to demonstrate the feasibility of nitrogen to ammonia conversion. Also, modelling on the interactions between light and the synthesized photocatalyst particle was examined for the light absorption. The optimum nitrogen fixation conditions have been examined, and the nitrogen fixation performance can reach up to 432 μg·gcat-1·h−1. Numerical simulations via the field-only surface integral method were also carried out to study the interactions between light and the photocatalytic particles to further confirm that it can be a useful material for photocatalyst. This newly developed Ti/Mo composites provide a simple and effective strategy for photocatalytic nitrogen fixation from air directly under ambient conditions.

Mechanism associated with the positive effect of nanocellulose on nitrogen retention in a manure composting system

Additives can play important roles in effectively inhibiting nitrogen losses during livestock manure composting due to the activities of microbes. This study investigated the effects of adding nanocellulose at 300 mg/kg, 600 mg/kg, and 900 mg/kg (NC900) on nitrogen conversion, nitrogen conversion functional genes, and related microorganisms during composting. The results showed that compared with the control, nanocellulose hindered the ammoniation reaction. In addition, NC900 promoted nitrification, interfered with the denitrification process, and reduced the abundance of the nirK gene, thereby increasing the nitrate nitrogen content and decreasing ammonia spillover. NC900 promoted nitrogen fixation by increasing the abundance of members of Rhizobiales, which play important roles in nitrogen fixation. In general, compared with the control, NC900 improved the retention of nitrogen by controlling ammonia emissions. The results obtained in this study demonstrate that nanocellulose can be applied in the treatment of organic solid waste and agricultural production.

Isolation and molecular characterization of domestic Bradyrhizobium species from soybean roots in the savannah soil of Nigeria

Abstract. The identification of effective indigenous strains of Bradyrhizobia could lead to the development of efficient and affordable inoculants for improving soil fertility. This can also promote nitrogen fixation in smallholder farming systems of Nigeria and as well make the use of nitrogen fertilizers unnecessary. This study was conducted to characterize and evaluate the nodulating properties of indigenous Bradyrhizobium species in soybean plant. A total of 18 strains were isolated using Bradyrhizobium japonicum selective medium (BJSM) from the root nodules of plants harvested from five sites on Ahmadu Bello University farm, Zaria Kaduna State, Nigeria. These isolates were evaluated for nodulating potential in a screen house using soybean (TGx 1448-2E) as a test crop. The total number of nodules, percentage effective nodules, nodule fresh and dry weights, shoot fresh and dry weight and plant nitrogen content were assessed. The nodules produced by the isolates showed high percentage effectiveness with isolate A4 having significantly higher nodule dry weight (78.00 mg) than the rest of the test isolates. The soybean inoculant, BIOFIX used in this study performed poorly having a nodule dry weight of 6.0 mg. There was positive and highly significant correlation between the nodule dry weight, shoot dry weight and plant nitrogen content (r=0.740, 0.641, 0.616, respectively) at p&lt;0.001. Sequence analyses were carried out on the high performing isolates from each site of sampling and the result obtained using the NCBI Database showed similarity of these isolates with reference strains belonging to the genus Bradyrhizobium (A4- Bradyrhizobium japonicum RV9, B2- Bradyrhizobium guangdongense CCBAU 51649, C1- Bradyrhizobium sp. UFLA05-149, D3- Bradyrhizobium sp. B918 and E3- Bradyrhizobium sp.UFLA05-149). A 16srRNA phylogenetic tree constructed with the sequences obtained grouped the isolates without any close reference strain. However, isolate B2 showed close affiliation with Bradyrhizobium guagdongense with 95% sequence identity. Based on the effectiveness of these five strains of Bradyrhizobium, it is suggested that they can be used as potential candidate for inoculants production.