This study investigated the simple correlation relationships between growth, yield, and yield-related traits in sorghum, aiming to identify key determinants for yield improvement. A randomized block design experiment, comprising ten treatments with three replications, was conducted at the Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj (U.P.). Treatments consisted of varying levels of Azotobacter chroococcum (10, 15, and 20 g/kg) and zinc (15, 20, and 25 kg/ha). Correlation analysis revealed significant positive correlations between sorghum grain yield and plant height, plant dry weight, ear head length, and test weight. Ear head length exhibited the highest individual contribution to yield, followed by plant height. Furthermore, plant dry weight and test weight also demonstrated positive contributions. Path analysis indicated that the highest combined contribution to yield was mediated through plant height via ear head length, followed by plant height via plant dry weight. These findings highlight the importance of plant height, ear head length, plant dry weight, and test weight as critical selection criteria for enhancing sorghum yield.

Ensuring the production of high-quality crops determines the need to develop new environmentally safe approaches in the biological control of the spread of phytopathogens. The aim of the work was to study the biocontrol properties of monocultures and complexes of the fungus Trichoderma atroviride and diazotrophic bacteria Fischerella muscicola and Azotobacter chroococcum in relation to the phytopathogen Fusarium culmorum R/z-16, to evaluate the environmental safety of the antagonist strains used. For the first time there has been studied the ability of T. atroviride complexes and diazotrophs to biocontrol F. culmorum, the main causative agent of root rot in grain crops, in the soil. A model experiment to identify the biocontrol activity of strains was carried out in microcosms with soil inoculated with the studied microbial cultures. After 45 days of incubation, spring wheat (Triticum aestivum L.) of the ‘Bazhenka’ cultivar was sown on the soil surface and 7 days after the sowing, the growth and infection rates of the seedlings were evaluated. It was found that the complexes of T. atroviride + A. chroococcum + F. muscicola, as well as T. atroviride + F. muscicola had the strongest biocontrol effect, which reduced the development of root rot by 4.12–4.97 times relative to the infectious background without the introduction of antagonists. Under the influence of trichoderma and diazotrophs on an infectious background, the dry weight of wheat seedlings increased by 72.9 % compared with soil inoculation with F. culmorum monoculture R/z-16. The ecological safety of filtrates of liquid cultures of T. atroviride K-01P (dilution 1:100), F. muscicola 300 (dilution 1:10-1:100) for the preparation Ecolume and Daphnia magna crustaceans has been confirmed. Field research data for 2022-2023 indicate the absence of a negative effect of T. atroviride K-01P and F. muscicola 300 on native representatives of micromycetes and ammonifying bacteria in the soil of the root zone of wheat. The results of the study expand traditional ideas about the possibility of using fungi of the genus Trichoderma and diazotrophs in the biological control of fungal phytopathogens and determine the prospects of using microbial complexes based on them in agriculture.

Background: Chickpeas are a prevalent and significant crop in the agricultural sectors of northern Iraq. In recent years, production has significantly declined due to diseases affecting chickpea plants. Investigating the pathogenic fungi responsible for these diseases is essential to restore production levels to their prior and improved states. Methods: Samples of diseased chickpea plants were collected from fields in the Erbil, Sulaymaniyah and Salah al-Din governorates in northern Iraq. Isolated associated fungi led to the identification of the dominant pathogenic species. A pathogenicity test was performed on the fungal isolates, showing the most aggressive strain for subsequent antagonism testing against three rhizobacterial isolates: Azotobacter chroococcum, Bacillus cereus and B. pumilus. This testing was conducted both in vitro and in a greenhouse setting, using single treatments and combinations. Result: The results showed that the pathogenic fungus Rhizoctonia solani was predominant, with the strain Srs-21 exhibiting the highest virulence in vitro. The three rhizobacterial isolates, A. chroococcum, B. cereus and B. pumilus, showed high efficacy in inhibiting the pathogenic fungus in vitro on potato dextrose agar (PDA) medium. In the greenhouse, the triple bacterial interaction treatment showed a seed germination rate of 100% and diminished disease incidence and severity to 0%, in contrast to the positive control treatment, which recorded 90% and 70%, respectively. It also showed the highest rate of rise in the dry weight of plants, signifying enhanced growth metrics.

The shift towards sustainable agriculture has intensified the use of liquid biofertilizers as alternative to synthetic fertilizers due to their role in improving soil health and plant nutrient uptake; but there are limited studies on their impact on the nutritional quality and toxicological safety of produce. This study is designed to assess the impacts of liquid biofertilizer on the nutritional and heavy metal concentrations of Okra (Abelmoschus esculentus) and Tomato (Solanum lycopersicum) crops. Okra and Tomato crops were treated with liquid biofertilizer containing microbial consortia (Aspergillus niger, Penicillium chrysogenum, Bacillus cerus, Bacillus licheniformis, Pseudomonas fluorescens and Azotobacter chroococcum). The proximate composition (%) for harvested Okra and tomato fruits treated with biofertilizer were; ash content (0.83±0.04 and 1.00±0.00); carbohydrate content (8.31±0.04 and 9.93±0.00); Fibre content (15.91±1.35 and 8.55±0.06); Lipid content (0.50±0.01 and 0.43±0.01); moisture content (98.60±0.03 and 87.45±0.02), protein content (6.52±0.02 and 5.66±0.04) and vitamin C content (Mg/Kg) (112.22±1.57 and 94.46±0.02) respectively. The heavy metal concentrations (mg/Kg) from harvested fruits ranged from 1.87±0.028 - 38.025±0.035; 0.00±0.00 - 4.46±0.269; 69.00±0.14 - 183.67±0.03 and 0.00±0.00 for Zinc, Lead, Iron and copper, respectively. Statistically, the treatments were significant at P<0.000 for concentrations of the heavy metals by the both plants. This study concludes that the use of the tested liquid biofertilizer is not only an effective strategy for boosting the productivity of okra and tomato but also a safe and valuable method for enhancing the nutritional value of the harvest, thereby recommending its integration into sustainable food production systems.

Solanum lycopersicum plants were grown in pots amended with biochar and PGPMs (plant growth-promoting microorganisms: Pseudomonas fluorescens and Azotobacter chroococcum), applied singularly and in combination, for three months, after which plants and soils were collected, divided into treatment groups based on organs, and analyzed. The following biochemical markers were studied: cellular respiration, shoot fresh and dry weight, root fresh weight, photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids), membrane lipid peroxidation, proline content, total antioxidant capacity (DPPH and ABTS assay), hydrogen peroxide, ascorbic acid, total phenolic content, enzymatic activity (SOD, POD, CAT, and APX), total soluble sugar content, and total protein content. Also, soil parameters, such as pH, EC, total enzymatic activity, active carbon, and respiration, were measured. While biochar alone induced root H2O2 accumulation, its co-application with PGPMs turned this signal into a systemic trigger for defense, enhancing the antioxidant capacity and the production of proline, phenolics, and ascorbic acid without causing oxidative damage. At the soil level, microorganisms counteracted biochar's inhibitory effects on enzymatic activity and intensified labile carbon use, indicating a more dynamic rhizosphere. Multivariate analysis confirmed that the combined treatment remodulated the plant-soil system, converting a stress factor into a resilience enhancer. This synergy underscores the role of biochar as an effective microbial carrier and PGPM consortia as bioactivators, together providing a powerful tool to prime crops against climate stress while preserving soil health.

PHAs are polyesters found as internal granules in several microorganisms. Azotobacter is known for its ability to produce PHA. This study aimed to isolate Azotobacter from the rhizosphere of selected crops located in Lima and evaluate their PHA-producing potential. Nile Red medium was used for PHA detection, and Sudan Black B staining allowed microscopic observation. Biopolymer production and quantification were carried out in Burk’s medium, PHA minimal medium (PHAMM), and modified PHAMM. In Nile Red medium, 68.2% of strains produced PHA, with Azotobacter AzoLur20 exhibiting the highest production, 2.1 g/L of PHA at 96 hours in PHAMM. However, strain AzoLur19 showed higher productivity and stability, achieving 0.06 g/L*h of PHA. Additionally, Sudan Black B staining in Burk’s medium revealed larger Azotobacter cells with more defined granules. AzoLur19 was classified as Azotobacter chroococcum. In conclusion, Azotobacter species isolated from crops located in Lima can produce PHA with high yields, with A. chroococcum as the predominant species. Highlights: A total of 22 Azotobacter strains were isolated, with A. chroococcum AzoLur19 identified as a promising PHA producer. PHA accumulation was successfully screened using Nile Red and Sudan Black B staining methods. AzoLur20 and AzoLur23 achieved high PHA yields, with up to 87.67% accumulation in Burk medium. AzoLur19 strain reached the highest productivity (0.06 g/L·h) in both PHAMM and modified PHAMM media. Modified PHAMM medium showed potential as an alternative for efficient PHA biosynthesis.

In the present study, phosphorus solubilizing bacteria were isolated from rhizosphere of the wheat plant. Altogether, 7 isolates were identified, out of which 3 belong to Azotobacter chroococcum, 2 to Pseudomonas fragi, 1 isolate from Azospirillum lipoferum and 1 isolated from Bacillus megaterium. Isolates identified on the basis of their morphology, biochemical test, sugar fermentation test, starch hydrolysis and gelatin liquefaction test. Production of phosphorus by individual isolates was tested on 5th , 10th and 15th day. It was observed that increase in duration resulted in dropping of pH. Maximum phosphorus was produced on 15th day in all isolates. The initial pH was adjusted to 7th but on 10th day, pH dropped to 6.5 and on 15th day, pH dropped to 6. Maximum phosphorus production was observed in isolate no. PF1 (4.31) of Pseudomonas fragi and minimum by isolate no. AZC3 (4.19) of Azotobacter chroococcum.. KEYWORDS :Phosphate solubilization, pH, Starch hydrolysis, Gelatin liquefaction test.

Isolation and Identification of Azotobacter chroococcum Strain and Measuring Microbial Respiration in Saline Soil

Cereal cyst nematode (Heterodera avenae) significantly hampers barley production by causing stunted growth and yield losses. This study explored the biocontrol potential of multitrait root endophytic bacteria isolated from H. avenae-infested barley roots to suppress nematode infestation. Ten endophytic bacterial strains were isolated and screened for their inhibitory effects on cyst hatching. Among them, Bacillus subtilis BREB 03 exhibited the highest hatching inhibition (48.31%), outperforming the bio-control check Azotobacter chroococcum HT-54. The promising root endophytic bacterium BREB 03, identified as a Gram-positive rod-shaped bacterium, exhibited optimal growth at 25°C and halotolerance up to 10% NaCl, along with diverse metabolic capabilities including positive catalase, oxidase, citrate utilization, and fermentation of multiple sugars. Whole-genome sequencing and phylogenomic analysis confirmed the identity of BREB 03 as B. subtilis. Further in vitro assays revealed BREB 03 capabilities for siderophore production, ammonia excretion, indole acetic acid (IAA) synthesis, and phosphorus solubilization, contributing to both nematode suppression and plant growth promotion. Seed treatment with BREB 03 significantly enhanced barley growth parameters, indicating its dual role as a biocontrol agent and biofertilizer. This study highlights B. subtilis BREB 03 as a promising alternative for sustainable management of cereal cyst nematode in barley, with potential to reduce reliance on chemical nematicides.

The living soil system is fundamental to sustainable agriculture, with soil quality reflecting environmental stability and food security. However, soil health is declining due to unsustainable practices and climatic stresses such as drought and salinity. Soil microorganisms play a vital role in nutrient mobilization, solubilization, and improved nutrient availability. The rhizosphere, a dynamic root zone, fosters crucial microbe - plant interactions that enhance soil biodiversity, disease suppression, and physicochemical properties like *Rhizobium spp.*, *Azotobacter chroococcum* which enhances nitrogen fixation, *Bacillus megaterium*, *Pseudomonas fluorescens* converts insoluble phosphate to soluble phosphorus form etc. Beneficial microbes like plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) boost crop productivity and tolerance to abiotic stress. Microbial communities also enhance soil structure, water retention, and organic matter dynamics. As sensitive indicators of soil health, microbes are key to sustainable agriculture. Future research should focus on identifying efficient microbial strains and understanding their metabolites to improve plant-soil interactions and support sustainable food production.

Chimonobambusa opienensis is a bamboo shoot species with considerable ecological and economic value; however, its low yield constrains large-scale cultivation. Bio-organic fertilizers, which are sustainable alternatives to chemical fertilizers, can improve soil conditions and enhance productivity. However, the mechanisms by which they increase yield through soil nutrient-mediated regulation of microbe–metabolite interactions in C. opienensis remain unclear. We conducted a two-year field trial with five fertilization treatments: organic fertilizer (OF), Azotobacter chroococcum (Ac), Bacillus amyloliquefaciens (Ba), organic fertilizer combined with (A) chroococcum (OF + Ac), and organic fertilizer combined with (B) amyloliquefaciens (OF + Ba). Amplicon sequencing and liquid chromatography–mass spectrometry were employed to assess the soil microbial composition and metabolic activity across treatments. The results demonstrated that soil chemical properties were the key drivers of microbial community structure. Co-occurrence network analysis revealed that microbial networks in the OF + Ac group were simpler and less interconnected than those in other treatments. Non-targeted metabolomics identified 133 soil metabolites. The control group was significantly enriched in fatty acyl compounds, whereas carbon- and nitrogen-containing metabolites were markedly increased in Ac and OF + Ac treatments. Moreover, the addition of A. chroococcum (in Ac and OF + Ac treatments) induced the most pronounced shifts in microbial community composition. Network analysis of microbial ASV–metabolite associations showed that nearly all differential ASVs responded specifically to either Ac or OF + Ac treatment. Furthermore, the network connector Bradyrhizobium (ASV2748) responded exclusively to OF + Ac and exhibited significant positive correlations with numerous nitrogen-containing metabolites. Structural equation modeling proposes a model that soil nutrients were the primary drivers of microbial community changes and directly enhanced bamboo shoot yield. This study proposes a model in which the OF + Ac enhances (C) opienensis bamboo shoot yield without compromising palatability, through a soil nutrient–microbe–metabolite pathway supported by SEM results, whereas Ba also increases yield but at the expense of palatability. These findings offer new insights into the interaction mechanisms among C. opienensi, soil microbiota, and metabolites.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07660-x.

Abstract Salinity stress poses a significant constraint on global productivity. This study was designed to investigate the combined effects of inoculation with Azotobacter chroococcum (Az) and soil amendment with biochar on the performance of rapeseed ( Brassica napus L.) under varying levels of NaCl-induced salinity. A factorial experiment evaluated key physio-biochemical responses, oxidative stress indicators, defense compound accumulation, and yield components. Salinity stress negatively impacted rapeseed growth, significantly reducing photosynthetic efficiency (Fv/Fm), chlorophyll content, relative water content (RWC), ATP levels, and ultimately grain and oil yields. Concurrently, salinity (120 mM and control treatments) increased indicators of oxidative damage — electrolyte leakage by 54%, malondialdehyde by 37% — and elevated levels of reactive oxygen species (O 2 •− at 97 µmol g −1 FW h −1 and H 2 ​O 2 ​ at 86 µmol g −1 FW). Additionally, it induced defense responses such as increased antioxidant enzyme activity and osmolyte accumulation. However, the co-application of Az and biochar significantly mitigated these adverse effects of salinity. Notably, the combined treatment, particularly Az inoculation with an elevated biochar application rate (20%), demonstrated synergistic effects. This combination significantly enhanced photosynthetic efficiency, improved plant water status, and augmented antioxidant defense systems as well as osmotic adjustment mechanisms (including soluble sugars, proline, etc.) relative to untreated plants under saline conditions. Under these conditions, grain and oil yields increased substantially by 16.8% and 12.6%, respectively, compared to untreated saline-stressed plants. These findings highlight the potential of combining Az inoculation with biochar application as a promising and sustainable strategy to improve salinity tolerance and enhance the productivity of rapeseed in salt-affected agricultural environments.

This study examines the impact of various bacterial types and mycorrhizal fungi on the growth and chemical composition of saffron (Crocus sativus L.) cultivated in calcareous soils of Iraq. Inoculation with Azospirillum brasilense increased daughter corm weight by 58 % compared with the control, followed by Pseudomonas aeruginosa (29 %). At the same time, Bacillus megaterium and Azotobacter chroococcum reduced growth. Combined bacterial inoculation resulted in a modest 12 % increase, while Glomus mosseae alone slightly decreased daughter corm weight (6 %). The interaction of G. mosseae with A. brasilense produced the highest improvement (65 %). The number of new corms doubled with P. aeruginosa but declined under mixed bacterial treatments due to competition. Parent corm dry weight rose with A. brasilense (9 %) and A. chroococcum (8 %), while B. megaterium reduced it by 38 %. Mycorrhizal inoculation enhanced parent corm dry weight by 40 %, with an additional 21 % increase when combined with bacteria. Leaf biochemical analysis showed higher nitrogen, phosphorus, and iron levels under microbial treatments, with G. mosseae notably enhancing phosphorus (5.39 mg/g). Potassium content was unaffected by microbial interactions. These results demonstrate that biofertilizers improve saffron growth, nutrient uptake, and metabolite accumulation, supporting its successful and economically viable cultivation in calcareous soils.

The present study investigates the effectiveness of microbiological preparations in enhancing growth and productivity of key agricultural crops, including barley, maize, sunflower, and root crops (table beet, sugar beet, and potato) under field conditions. The experimental design included four replicates per treatment, with statistical analysis. For maize, the application of microbial consortia resulted in significant improvements in biometric and yield parameters compared to the untreated control. The most pronounced effect was observed with Preparation No.1 ( Azotobacter chroococcum MDC 6111 in combination with Pseudomonas tritici MDC 9168), which increased plant height by 31.4%, ear mass by 63.2%, and 1000-grain weight by 35.1%, corresponding to a total yield increase of 35.1%. In sunflowers, similar trends were detected. Preparation No.1 led to a 24.8% increase in plant height and a 56.1% increase in 1000-seed weight. Preparation No.3 ( Azotobacter chroococcum MDC 6111) also demonstrated a notable positive effect (yield increase of 42.3%), while Preparation No.2 (commercial mineral fertilizer “Nitroammophoska”) showed only marginal improvement. Regarding root crops, Preparation No.1 markedly enhanced productivity. In table beet, yield reached 14.51 ± 0.91 kg/10 m 2 versus 5.89 ± 0.42 kg/10 m 2 in the control. Sugar beet yield increased by 2.4-fold, and potato yield by 27.9%. Preparation No.2 showed moderate effectiveness in beets. These findings emphasizing the role of rhizosphere microorganisms in nutrient mobilization, hormonal regulation, and stress resistance. The study supports the use of microbial inoculants, particularly Preparation No.1, as a sustainable tool to improve crop productivity in diverse agroecosystems.

IntroductionSalinity stress severely restricts plant growth and yield, reducing global crop productivity. Ensuring food security requires sustainable strategies to mitigate salinity damage. Beneficial microorganisms used as biofertilizers enhance plant tolerance to abiotic stresses. This study examined the response of spring wheat (Triticum aestivum L. cv. Yecora Rojo) to biofertilizers under varying salinity levels to assess their potential in enhancing salt stress tolerance.MethodsThree treatments were applied: untreated control (C), grain treatment (GT), and grain plus root treatment (GRT). Salinity stress was imposed using diluted seawater at 0, 2000, 4000, and 6000 ppm. The biofertilizer formulation included Azotobacter chroococcum, Bacillus megaterium, and Bacillus circulans. Physiological traits (chlorophyll, cell membrane stability, relative water content), biochemical markers (proline, malondialdehyde, hydrogen peroxide), and antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase) were measured. Expression of salinity-responsive genes (TaCAT1, TaPOD-D1, TaSOD2, TaHKT1;4, TaNHX2, TaP5CS, TaFER-5B) was also analyzed.ResultsSalinity significantly reduced wheat growth, chlorophyll levels, membrane stability, and water content. Biofertilizer treatments, especially GRT, alleviated these effects by maintaining chlorophyll and water status while reducing oxidative damage. Antioxidant enzyme activities increased, improving scavenging of reactive oxygen species. Biofertilizers also upregulated stress-related genes, enhancing osmotic adjustment, ion balance, and antioxidant defenses. Correlation analysis confirmed strong physiological and biochemical interactions supporting stress tolerance.Discussion & conclusionBiofertilizers represent an eco-friendly and sustainable strategy to enhance wheat salinity tolerance. By boosting antioxidant defenses, osmolyte accumulation, and ion regulation, they mitigate salt-induced damage. GRT provided the greatest benefit, highlighting the synergistic effect of dual grain and root inoculation.

Wheat (Triticum aestivum L.) is the major grain crop that ensures global food security. Intensive farming often involves overuse of mineral fertilizers and pesticides, which leads to soil degradation and environmental pollution. Microorganisms and natural sorbents, e.g., zeolite, offer an alternative solution to the crop yield problem. Zeolite improves the soil structure while helping to retain moisture and nutrients. Growth-stimulating bacteria increase the availability of nutrients for plants and stimulate their growth. This research featured the effect of the combined use of zeolite and bacteria on different wheat varieties and growth indicators in laboratory conditions. The experiment involved spring wheat varieties of Sibirskiy Alyans, Pamyati Afrodity, and Nadezhda Kuzbassa. The list of growthstimulating bacteria included Azotobacter chroococcum B-4148, Azotobacter vinelandii B-932, and Pseudomonas chlororaphis subsp. aurantiaca B-548, as well as their consortium (1:3:1). The indicators to be checked included the solubilizing activity of the strains and the effect of zeolite (1 t/ha) and bacterial preparations on wheat growth. All bacteria solubilized zeolite (2.5–17.7 mm). The highest activity belonged to P. chlororaphis subsp. aurantiaca B-548 (17.7 mm). The combined application of zeolite (1 t/ha) and the bacterial consortium had a positive effect on the growth and development of all wheat varieties. The Sibirskiy Alyans variety showed a germination rate of 86%, a shoot length of 183 mm, a dry weight of 42.4%, a chlorophyll content of 24.47%, a carotenoid content of 16.21%, and a nitrogen concentration of 51.83%. The Pamyati Afrodity variety demonstrated 80% germination rate, 157 mm shoot length, 31.3% dry weight, 32.07% chlorophylls, 19.40% carotenoids, and 59.35% nitrogen. The Nadezhda Kuzbassa variety had 98% germination rate, 185 mm shoot length, 41.2% dry weight, 39.74% chlorophylls, 28.47% carotenoids, and 55.26% nitrogen. The results confirmed the i ndustrial efficiency of zeolite and bacteria in wheat farming, as did other reports on their positive effect on crop yield. However, further field trials are needed to confirm the results in conditions close to reality.

Soil salinity disrupts rhizosphere interactions, impairing root–microbe symbioses, nutrient uptake, and water relations in onion (Allium cepa L.) and garlic (Allium sativum L.). This study evaluated the efficacy of biofertilizers (Azotobacter chroococcum SARS 10 and Azospirillum lipoferum SP2) and organic amendments (sewage sludge and poultry manure) in salt-affected soils in Kafr El-Sheikh, Egypt. Five treatments were applied: (T1) control (no amendments); (T2) biofertilizer (3 L/ha for onion, 12 L/ha for garlic) + inorganic P (150 kg/ha P2O5 for onion, 180 kg/ha for garlic) and K (115 kg/ha K2SO4 for onion, 150 kg/ha for garlic); (T3) 50% inorganic N (160 kg/ha for onion, 127.5 kg/ha for garlic) + 50% organic manure (6000 kg/ha for onion, 8438 kg/ha for garlic) + P and K; (T4) biofertilizer + T3; and (T5) conventional inorganic NPK (320 kg/ha N for onion, 255 kg/ha N for garlic + P and K). Soil nutrients (N, P, K), microbial biomass carbon (MBC), dehydrogenase activity, and microbial populations were analyzed using standard protocols. Plant growth (chlorophyll, photosynthetic rate), stress indicators (malondialdehyde, proline), and yield (bulb diameter, fresh yield) were measured. Treatment T4 increased MBC by 30–40%, dehydrogenase activity by 25–35%, available N (39.7 mg/kg for onion, 35.7 mg/kg for garlic), P (17.9 mg/kg for onion), and K (108 mg/kg for garlic). Soil organic matter rose by 8–12%, and cation exchange capacity by 26–36%. Chlorophyll content improved by 25%, malondialdehyde decreased by 20–30%, and fresh yields increased by 20–30% (12.17 tons/ha for garlic). A soybean bioassay confirmed sustained fertility with 20–25% higher dry weight and 30% greater N uptake in T4 plots. These findings highlight biofertilizers and organic amendments as sustainable solutions for Allium productivity in saline rhizospheres.

Intensifying agricultural production involves an active use of agrochemicals, which results in disrupted ecological balance and poor product quality. To address this issue, we need to introduce biologized science-intensive technologies. Bacteria belonging to the genera Azotobacter and Pseudomonas have complex growth-stimulating properties and therefore can be used as a bioproduct to increase plant productivity. We aimed to create a growth-stimulating consortium based on the strains of the genera Azotobacter and Pseudomonas, as well as to select optimal cultivation parameters that provide the best synergistic effect. We studied strains Azotobacter chroococcum B-4148, Azotobacter vinelandii B-932, and Pseudomonas chlororaphis subsp. aurantiaca B-548, which were obtained from the National Bioresource Center “All-Russian Collection of Industrial Microorganisms” of Kurchatov Institute. All the test strains solubilized phosphates and produced ACC deaminase. They synthesized 0.98–1.33 mg/mL of gibberellic acid and produced 37.95–49.55% of siderophores. Their nitrogen-fixing capacity ranged from 49.23 to 151.22 μg/mL. The strain had high antagonistic activity against phytopathogens. In particular, A. chroococcum B-4148 and A. vinelandii B-932 inhibited the growth of Fusarium graminearum, Bipolaris sorokiniana, and Erwinia rhapontici, while P. chlororaphis subsp. aurantiaca B-548 exhibited antagonism against F. graminearum and B. sorokiniana. Since all the test strains were biologically compatible, they were used to create several consortia. The greatest synergistic effect was achieved by Consortium No. 6 that contained the strains B-4148, B-932, and B-548 in a ratio of 1:3:1. The optimal nutrient medium for this consortium contained 25.0 g/L of Luria-Bertani medium, 8.0 g/L molasses, 0.1 g/L magnesium sulfate heptahydrate, and 0.01 g/L of aqueous manganese sulfate. The optimal cultivation temperature was 28°C. The microbial consortium created in our study has high potential for application in agricultural practice. Further research will focus on its effect on the growth and development of plants, in particular cereal crops, under in vitro conditions and in field experiments.

Abstract The study was at a Orchard Development Project in Um Ghragher area / Al-Husseiniya District / Karbala Governorate Throughout the 2024 cultivation season to investigate the impact of humic acid and biofertilizers on the qualitative traits and productivity parameters of Barhi date palms. The experiment was conducted as a factorial arrangement in(RCBD), comprising two factors: the first factor the was application of humic acid at four different concentrations (0, 5, 10, and 15 g.20 L. per palm-1), Whereas the second factor was involved the application of biofertilizer at four concentrations:(no addition, Azotobacter chroococcum at 150 mL.20 L. per palm−1, Bacillus megatherium at 150 mL.20 L. per palm−1, and a mixture of (Azotobacter chroococcum 75 mL + Bacillus megatherium 75 mL).20 L.per palm-1 Results showed ground addition treatment with humic acid applied at a concentration of (15 g 20 L. per palm-1), resulted in significantly higer values compared to other treatments, recording the highest averages for all studied traits:(fruit weight, fruit volume, total sugars, fruit set percentage, bunch weight, and total yield). By comparison, the control treatment recorded the least values. Similarly, the B3 treatment (combined biofertilizers) significantly all other biofertilizer treatments, recording the highest averages in the same parameters compared to the control. Moreover, the combined interaction treatment Adding humic acid 15 g 20 L. per palm−1 and bio-fertilizer (Azotobacter chroococcum concentration of 75 ml + Bacillus megatherium concentration of 75 ml) 20 L. per palm-1significantly all other combinations record in with the highest averages for all studied traits, whereas the control combination had the least.

An important stage in the development of an effective biological preparation for agricultural crops is the selection of an optimal nutrient medium that would meet the physiological needs of microorganisms and ensure the implementation of their agronomically important functions as biological agents of the inoculant. The growth characteristics of A. chroococcum IMV B-7836 in liquid media of different chemical composition were studied. The optimal digest medium for the production of the preparation was selected, the chemical compositions of which provides the maximum titer of A. chroococcum IMV B-7836 in the optimal terms of diazotroph cultivation. We studied the dependence of the generation of the number of viable cells of A. chroococcum IMV B-7836 on the time of cultivation in batch culture on modified molasses medium, Ashby’s, and pea medium. It was shown that bacterization of cucumber seeds with a new effective inoculant based on A. chroococcum IMV B-7836 promotes better growth and development of plants, and increases nitrogenase activity in the root zone of vegetable plants and an increase in yield during early and presowing bacterization. Upon early and presowing bacterization of cucumber seeds, nitrogen-fixing activity was at the level of 46.1–47.6 nmol С2Н4/g dry soil per hour in the flowering phase. The yield of the Konkurent variety cucumber upon early and presowing treatment with an inoculant based on A. chroococcum IMV B-7836 for three years increased by 15.1% compared to the control.