Synergistic Effect of Microbial Biostimulants Arthrobacter pascens and Bradyrhizobium japonicum, as the Primary Driver of Climate-Resilient Soybean Productivity at 55° N Latitude in Europe

Soil Microbiota-Mediated Effects on Soybean (Glycine max (L.) Merr.) Growth and Yield: The Role of Bradyrhizobium japonicum and Trichoderma in Sustainable Agricultural Systems

Soybean (Glycine max (L.) Merr.) is a key legume with high agronomic and nutritional value, widely cultivated for its high-protein seeds and its capability to improve soil fertility through biological nitrogen fixation. Recently, co-inoculation strategies combining Rhizobia bacteria with growth-enhancing fungi from the genus Trichoderma have gained increasing attention as a way to enhance soybean productivity and resilience under variable environmental conditions. The present study, conducted in 2023–2024, examined how seed inoculation treatments (Bradyrhizobium japonicum and Trichoderma viride) affect soybean productivity, seed quality, and soil biochemical changes expressed as the activity levels of selected soil enzymes—dehydrogenases (DHA), catalase (CAT), acid phosphatase (ACP), and alkaline phosphatase (ALP)—as well as the biological fertility index (BIF). The findings indicated that co-inoculation positively influenced plant productivity and produced the highest seed yields among all treatments tested, exceeding the control by 25.6%. Furthermore, inoculated seeds were characterized by improved seed quality, expressed by higher germination capacity (80%) and greater average seedling length (4.74 cm). The bacterial strains used to inoculate soybean seeds increased soil biochemical activity and improved fertility, particularly under unfavorable rainfall distribution during the growing season. Co-inoculation can be recommended as an effective and environmentally friendly element of soybean cultivation technology, supporting yield stability in variable weather conditions. Further research is recommended in longer multi-year series and under various habitat conditions.

The Role of Arthrobacter pascens 13LEP5 in mitigating Drought and Cold stress in Soybean (Glycine Max (L.) Merr.)

Drought and low temperatures are major abiotic factors affecting key physiological and biochemical processes and limiting the yields of soybean (Glycine max L. Merr.). To in-crease soybean production in Europe, different agricultural strategies are applied to re-duce abiotic stress, including biostimulants. Therefore, studies on the effectiveness of local strains isolated in Europe are becoming increasingly relevant. In this study two bacterial strains Arthrobacter pascens (AP) and Bradyrhizobium japonicum (BJ) along with plant-derived protein hydrolysate (PH) were analysed with soybean plans under abiotic stress conditions in plant growth chambers. Six treatments (control; AP; BJ; PH; BJ+AP; BJ+AP+PH) were tested to evaluate biostimulation effect before stress induction (VC stage) and to determine stress reduction effect on soybeans after plants recovery period (V3 stage). Biostimulants application has positive effect on soyabean biometric parameters in early plant development stage and post stress periods. More stable long-term effect was found on structural plant development parameters, than on pigment accumulation. The best results on plant biometric parameters were found where (AP) and (BJ+AP+PH) com-bination was inoculated. (BJ+AP+PH) combination was the only effective treatment, which showed significantly different results in pigments indices, compared to the control, after stress period. Author summary Yasha Jamil: Conceptualization, Data curation, Formal analysis, Writing– original draft, Giuseppe Colla: Formal analysis, Writing– original draft, Writing– review & editing, Justina Kaziuniene: Data curation, Formal analysis, Sarune Ramoskaite :Writing– review & editing. Monika Toleikienė: Conceptualization, Data curation, Formal analysis, Writing– original draft, Funding acquisition, Supervision, Writing– review & editing.

Effect of Biofertilization with Plant Growth-Promoting rhizobacillus (PGPR) on Growth and Productivity of maize (Zea mays L.) Compared to Chemical Fertilization

Background: Maize (Zea mays L.) is one of the world's most important cereal crops, and improving its productivity while reducing dependence on chemical fertilizers has become a major goal of sustainable agriculture. The potential role of plant growth promoting rhizobacteria (PGPR) as a biofertilizer evolved as appropriate substitute to neutralize adverse environmental impacts wielded by manmade agrochemical. Objective: This study aimed to evaluate the effects of Pseudomonas fluorescens and Bacillus subtilis, individually and in combination, on the growth and yield of maize compared with conventional NPK fertilization. Methods: A field experiment was conducted during the 2025 growing season at the Field Crops Research Station, College of Agriculture, University of Samarra, using a Randomized Complete Block Design (RCBD) with three replicates. Six treatments were evaluated: Untreated control (T1), Pseudomonas fluorescens (T2), Bacillus subtilis (T3), combined inoculation (P. fluorescens + B. subtilis) (T4), combined inoculation with NPK fertilizer (T5), and NPK fertilizer (20:20:20) only (T6). Vegetative growth and yield-related traits were recorded and statistically analyzed. Results: Inoculation of plants with PGPR bacteria resulted in a significant improvement in both vegetative growth and yield compared to the untreated control group. Pseudomonas fluorescens (T2) exhibited the highest vegetative growth rate, recording the highest plant height (148.00 cm), leaf area (365.00 cm²), leaf area index (2.63), and number of grains per spike (688 grains) compared control group recorded (92.33 cm), (10.67 plant⁻¹), (151.73 cm²), (0.70) respectively. Bacillus subtilis (T3), achieved the highest productivity, producing the largest number of spikes per plant (2.67 spikes) and the highest spike weight (283.50 g) compared control group recorded (2.00) and (161.60 g). Conclusion: The use of PGPR, and especially Pseudomonas fluorescens and Bacillus subtilis as potential biofertilisation agents is a promising sustainable alternative to chemical fertilisation that can enhance maize growth and production, while decreasing dependence on mineral fertilisers.

Biofertilization with Gluconacetobacter diazotrophicus: Effects of a Native Isolate and a Reference Strain on Soil and Foliar Chemical Profiles and Economic Performance in Greenhouse Tomato Production

The intensive use of synthetic fertilizers in horticulture generates environmental and economic constraints, highlighting the need for sustainable alternatives such as plant growth-promoting bacteria. However, their effectiveness depends on strain adaptation to local conditions. This study evaluated the effect of Gluconacetobacter diazotrophicus (native isolate GIBI029 vs. reference strain ATCC 49037) under four nitrogen (0 and 100% of the recommended dose) and phosphorus (0 and 100% of the recommended dose) fertilization combinations on soil chemical properties, foliar nutrient uptake, and economic performance in greenhouse tomato production in Colombia. The native isolate was associated with higher soil nutrient levels, reaching 185.1 g/kg organic matter, 6.4 g/kg total nitrogen, 284.75 mg/kg available phosphorus, 9.32 cmol/kg calcium, and 3.93 cmol/kg magnesium. In addition, foliar nitrogen content reached 22.4 g/kg in treatments inoculated with GIBI029. These responses were associated with yields up to 106.4 t/ha, exceeding those obtained with the reference strain. Yield data were obtained from a previous study conducted under the same experimental design and environmental conditions and were incorporated here exclusively for the economic assessment. Economically, the native isolate achieved the highest benefit–cost ratio (2.65) and net income (USD 20,106/ha). A strong correlation between soil organic matter and nitrogen (r = 0.99) was observed, indicating a close association between these variables within the evaluated production system. These results suggest that strain origin may influence biofertilization efficiency and indicate that native microbial inoculants can contribute to improved agronomic and economic performance under the conditions evaluated, supporting their use in sustainable tomato production systems.

Agro‑ecological and Genetic Drivers of Symbiotic Efficiency of Indigenous Rhizobium etli Strains in Common Bean in Southern Ethiopia

Do Biofertilisers Increase Productivity in Leguminous Crops? A Critical Review of Rhizobial Inoculation, Microbial Consortia and Field-level Yield Responses

Biofertilisers are promoted as low-input tools for increasing legume productivity, yet the category encompasses biologically distinct interventions whose field performance is not equally reliable. This critical narrative review evaluates whether microbial inoculants increase the productivity of grain and forage legumes, with particular emphasis on harvestable yield rather than nodulation or vegetative growth alone. Literature published principally from 1990 to 21 June 2026 was appraised alongside selected foundational studies. Evidence was synthesised across rhizobial inoculation, plant growth-promoting rhizobacteria, phosphorus-solubilising bacteria, arbuscular mycorrhizal fungi, Trichoderma and multi-organism co-inoculation. The strongest evidence supports compatible, effective rhizobial inoculation when indigenous rhizobia are absent, sparse, poorly competitive or inefficient and when other constraints to biological nitrogen fixation are not dominant. Large on-farm datasets and field experiments show meaningful average yield gains in soybean and chickpea, but also wide site-to-site variation. By contrast, non-rhizobial co-inoculants often increase nodulation, root growth or biomass more consistently than grain yield. Meta-analyses of soybean co-inoculation illustrate this distinction: improvements in intermediate traits may occur without a statistically reliable increase in harvested yield, while other datasets show only modest additional yield beyond conventional rhizobial inoculation. Fungal partners can enhance phosphorus acquisition, symbiotic functioning and disease suppression, but responses depend strongly on soil phosphorus, native microbial communities, crop genotype, water status and formulation quality. Across inoculant classes, controlled-environment effects tend to exceed field effects, indicating that colonisation, competition, environmental stress and agronomic co-limitations constrain translation. Biofertilisers therefore do increase legume productivity under identifiable conditions, but they are not universally effective substitutes for balanced soil fertility management. Future progress requires multi-site, multi-season trials with robust comparators, molecular tracking of inoculant occupancy, strain-by-genotype-by-environment matching, product-quality verification and endpoints centred on yield stability, nutrient-use efficiency and farm-level value.