TL;DR
It is suggested that Bacillus strains possess PGP properties under metal stress conditions, indicating their potential for application in the remediation of metal-contaminated soils and enhancement of plant growth.
Soil salinity remains a major abiotic factor limiting agricultural productivity worldwide, with the situation worsening in parts of Maharashtra, particularly Karad Taluka. This study examined saline soils from various locations within Karad, assessing their physicochemical properties and isolating indigenous halotolerant bacterial strains that exhibit plant growthpromoting rhizobacterial (PGPR) traits. The soil analysis revealed highly alkaline pH levels (8.8-9.4), elevated sodium concentrations, and deficiencies in organic carbon, nitrogen, and micronutrients. Five halotolerant bacterial isolates (Ko1, Va1, Be1, Vm1, and At1) were obtained and evaluated for PGPR activities such as phosphate and potassium solubilization, nitrogen fixation, indole-3-acetic acid (IAA) production, and siderophore synthesis. All isolates demonstrated positive results in phosphate and potassium solubilization, nitrogen fixation, and IAA production, with four also producing siderophores. Notably, isolates Be1, Vm1, and At1 showed strong performance across multiple traits, highlighting their potential as bioinoculant candidates. These findings suggest that native halotolerant PGPR strains from Karad Taluka could enhance soil fertility, improve nutrient uptake, and support plant growth in saline conditions. Future research including field trials and molecular characterization could facilitate the development of environmentally sustainable microbial formulations for saline agriculture.
It is suggested that selected halotolerant isolates possess multifunctional traits including salt tolerance and potential nutrient-solubilizing capacity, making them promising candidates for biofertilizer development and sustainable agriculture in salt-affected regions.
Remediating calcareous soils co-contaminated with copper and arsenic remains a major challenge due to low metal bioavailability and the risk of chelator-induced phytotoxicity, which can severely limit phytoremediation success. This study investigated a synergistic strategy combining heavy metal-resistant plant growth-promoting rhizobacteria (PGPR) with precisely timed ethylenediaminetetraacetic acid (EDTA) application to improve phytoextraction efficiency in corn (Zea mays). Eight PGPR isolates were obtained from contaminated soil, and three strains (Stenotrophomonas sp. A22, Pseudomonas sp. A2 and A5) were selected based on their high resistance to Cu (up to 400 mg L-1) and As (up to 250 mg L-1), as well as multiple plant growth-promoting traits. In a controlled pot experiment, we evaluated bacterial inoculation and EDTA application at 20, 35, or 45 days after planting on plant growth, physiological performance, and metal uptake. Early EDTA addition (day 20) caused severe phytotoxicity, markedly reducing root and shoot biomass and depressing photosynthetic efficiency (Fv/Fm). In contrast, delaying EDTA application to days 35 or 45 substantially alleviated these adverse effects. PGPR inoculation, particularly with strain A5, further mitigated EDTA-induced stress and improved biomass production and physiological status. The combined PGPR-EDTA treatments significantly increased soil metal bioavailability and enhanced plant uptake, with maximum shoot Cu (214 mg kg-1) and As (99 mg kg-1) concentrations observed with strains A5 or A2 and EDTA application at day 20. Sequential extraction confirmed that these PGPR-EDTA treatments shifted metals from residual and oxide-bound pools into more soluble and exchangeable/carbonate-bound fractions. The findings support a mechanistically informed, optimized phytoremediation strategy for calcareous soils, based on the optimal timing of EDTA application and inoculation with metal-resistant PGPR.
This study evaluated the effects of sewage sludge composted (SSC, mixed with sugarcane bagasse at 1:1 ratio) and microbial biopromoters on soil fertility and early growth of Astronium fraxinifolium, a native tree with high recovery potential in the Brazilian Cerrado. In a randomized block design (2 × 4 factorial), treatments consisted of two SSC levels (with and without 23 g pot⁻¹ of chemically characterized, environmentally safe compost) and four inoculation treatments (control; Bacillus subtilis - BS; Rhizophagus clarus - RhC; and BS + RhC) with five replicates in 6-L pots. After 150 days, growth, root morphology, gas exchange, and soil properties were evaluated. SSC improved soil fertility (reduced aluminum, increased P, sum of bases, base saturation, and essential micronutrients Fe, Mn, Zn) without inducing heavy metal toxicity, increasing plant height. The SSC + RhC interaction significantly promoted shoot and root biomass, stem diameter, and root surface area/volume. Seedling Quality Index (SQI) was highest under SSC + RhC and SSC + BS. Furthermore, SSC and inoculants significantly enhanced gas exchange parameters, translating into substantially higher photosynthetic performance. Overall, combining this specific SSC rate with biopromoters, particularly Rh. clarus, effectively improved soil chemical properties and seedling vigor. While limited to nursery conditions, these findings demonstrate that this approach successfully promotes high-quality seedlings, establishing a promising baseline for future long-term field validation and dose-response trials in degraded lands.
Wastewater containing heavy metals can lead to soil and crop accumulation, thus posing a risk to the environment. Biochar, being a rich carbon-containing organic fertilizer, can reduce these adverse impacts by increasing soil fertility. This study was conducted to assess the biochar-treated wastewater for beetroot cultivation using Beta vulgaris L. at three locations in Faisalabad, namely, Directorate of Farms UAF, Uchkera Farm, and Satyana Farm, Faisalabad, using an RCBD factorial design with three wastewater treatments, namely, UAF sewage, Madhuana, and Paharang drains. As a result, pigments increased (Chl a/b 25%, carotenoids 25%), and physiological charac - teristics improved (RWC 25%, electrolyte leakage -20%). The elevated levels of heavy metals were lowered by biochar. Heavy metal buildup in beets was significantly enhanced by wastewater irrigation, but most metals were successfully reduced by applying biochar, improving crop safety and lowering environmental risk. In general, 2024 performed better than 2023. While biochar further improves performance and reduces the dangers of heavy metals, wastewater irrigation increases beetroot growth, yield, and stress tolerance, encouraging safer and more sustainable crop production.
Simultaneously removing petroleum hydrocarbons (PHCs) and heavy metals from soil is a challenging task. This study aimed to evaluate the efficacy of green-synthesized nano zero-valent iron (nZVI) particles and a microbial consortium in combination with sunflower ( Helianthus annuus L.) plants for nano-enhanced bioremediation of soil co-contaminated with PHCs and cadmium (Cd). A pot trial was conducted by growing sunflower plants on soil co-contaminated with 6000 mg kg -1 and 30 mg kg -1 of PHCs and Cd, respectively, and nZVI particles and a microbial consortium were added to the soil for plant growth enhancement and pollutants removal. The results revealed that the co-contaminated soil caused significant phytotoxicity to sunflower plants. However, the co-application of a microbial consortium and nZVI particles considerably alleviated the phytotoxic impacts of Cd and PHCs on sunflower plants, demonstrating up to 72.7% and 83.5% improvements in plant physiology and growth in contaminated soil, respectively compared to the respective unamended control. Furthermore, the combined application of a microbial consortium and nZVI particles caused 59.4% and 58.6% reduction in bioavailable Cd, and 82.7% and 74.7% decrease in PHCs in planted and unplanted treatments, respectively, with respect to their initially applied concentrations. The findings from this study indicate that the integrated application of nZVI particles and a microbial consortium was very effective in improving plant growth, mitigating Cd-accumulation in plants, confirming Cd-immobilization, and removing PHCs from soil, highlighting the potential of nano-enhanced bioremediation as a sustainable solution for the treatment and management of soil co-contaminated with inorganic and organic pollutants.