Agronomy

Soybean (Glycine max) is a globally important crop, but its productivity is often limited by suboptimal nodulation and nitrogen fixation, particularly under stress conditions. Bradyrhizobium diazoefficiens strain USDA110 is widely applied to enhance nodulation, yet its efficiency can be further improved by phytohormone modulation. This study examined the effects of seed coatings containing plant growth regulators (PGRs)—acetylsalicylic acid (ASA), aminoethoxyvinylglycine (AVG), Indole-3-butyric acid (IBA), and 6-benzylaminopurine (BAP)—at varying concentrations (5, 50, and 500 nM), in combination with USDA110, on nodulation, nitrogenase activity, ethylene emission, physiological traits, and yield of soybean cultivar CM60. Laboratory assays identified 50 nM AVG, 5 nM IBA, and 5 nM ASA as optimal treatments, significantly enhancing nodule number and nitrogenase activity more than 32% and 28%, as, respectively, compared to untreated seeds. Greenhouse trials in pots, both under well-watered and water stress conditions, showed that USDA110 + AVG/IBA significantly improved photosynthetic rate (+21 and +18% compared to USDA110 alone) and increased plant height. Notably, USDA110 + AVG/IBA treatments sustained higher seed weight under drought, increasing it by over 25%, indicating strong synergistic effects in mitigating stress impacts. These findings highlighted that integrating USDA110 with specific PGRs represented a promising strategy to optimize nitrogen fixation and enhanced soybean productivity under both favorable and challenging conditions.

Agricultural production is consistently threatened by stressors such as salinity. Few studies have reported on the released antioxidative enzymes and the salinity-responsive genes identified using RNA sequencing and de novo assembly in maize. To further understand the harmony between stressing the maize with a NaCl solution as a compensatory water-irrigation method and spraying regulatory zinc oxide nanoparticles (ZnO/NPs), the salinity-responsive genes were analyzed using RNA sequencing and bioinformatics tools, and the antioxidant enzymatic activities were determined. Differential expression analysis was used to uncover genes that were up-/down-regulated during the experiment. The regulatory pathways and functions of differentially expressed genes (DEGs) were estimated. Glutathione reductase/-s-transferase (GR/GST), peroxidase (POX), superoxide dismutase (SOD), and catalase (CAT) enzymes were determined spectrophotometrically. Mitigating salinity stress with 150 mM NaCl led to significant oxidative stress, markedly elevating enzyme activities: POX and GST by 275% and 254%, GR by 166%, CAT by 91%, and SOD by 56%. Treatment with ZnO/NPs alleviated this stress, decreasing enzyme activity by 61% for GST, 55% for POX, 38% for CAT, 28% for SOD, and 25% for GR. The results of RNA-seq revealed candidate genes related to changes in stressed/non-stressed maize plants, regardless of whether they were sprayed with the nanoparticles or not. This study’s results offer novel insights into the genetic traits of maize subjected to salinity stress and ZnO/nanoparticle application, thereby advancing the comprehension of how ZnO/nanoparticles might alleviate the detrimental impacts of salinity on plants whose properties were enhanced to be used in the eco-friendly synthesis of nanoparticles that were used as a bio-fertilizer in priming plants.

Petroleum hydrocarbons are pervasive soil pollutants that detrimentally affect the soil structure, nutrients, and microbial ecosystems. However, the effect of biochar particle size on the remediation effectiveness remains a critical, unresolved parameter. Here, a soil remediation experiment was conducted to evaluate the synergy between biochars of different particle sizes and nutrient addition. Total petroleum hydrocarbons (TPHs) were quantified gravimetrically, and specific hydrocarbon fractions were analysed via gas chromatography mass spectroscopy (GC‒MS) while the microbial community composition was analysed via high-throughput sequencing. The results revealed that granular bulrush straw biochar (0.85 mm) with nutrients achieved the greatest TPH degradation (73.35%), significantly outperforming both powder biochar and soybean straw biochar. This enhanced remediation was associated with a significant shift in the microbial community (p < 0.05), characterized by substantial increases in hydrocarbon-degrading bacteria, particularly Actinobacteria and the genus Mycobacterium. This study revealed that the synergistic application of granular biochar and nutrients is a highly effective, nature-based strategy for petroleum-contaminated soil, which functions by resolving a critical biochar parameter to enhance key microbial degraders.