Harnesting Plant Growth Promoting Rhizobacteria to Improve Soybean Agronomic Performance in Salinity Stressed Soils

Abstract

Climate change has worsened soil salinity through rising temperatures, sea water intrusion, irregular rainfall patterns, and increased evapotranspiration, making salinity one of the major constraints in soybean cultivation worldwide. Salinity stress inhibits plant growth, disrupts nutrient uptake, reduces photosynthesis, induces oxidative stress, and ultimately decreases crop productivity. In addition, excessive salt accumulation deteriorates soil structure, suppresses beneficial microbial activity, and limits nutrient availability, thereby threatening soil health and sustainable agricultural production. Plant Growth Promoting Rhizobacteria (PGPR) can be utilized as an environmentally friendly alternative approach to enhance plant tolerance to saline conditions while reducing dependence on chemical fertilizers and other external inputs. This review examines the extent to which beneficial rhizobacteria improve soybean growth and productivity under salinity stress conditions. The method employed was a systematic literature review combined with bibliometric analysis based on network visualization using VOSviewer. Literature sources were obtained from Scopus covering the period 2020–2026, with article selection conducted using inclusion and exclusion criteria, resulting in 22 relevant articles. The findings indicate that bacteria such as Bradyrhizobium japonicum, Bacillus subtilis, Pseudomonas fluorescens, Azospirillum brasilense, and several other halotolerant bacteria significantly improve soybean tolerance to salinity stress through phytohormone production, biological nitrogen fixation, phosphate solubilization, regulation of Na⁺/K⁺ ion balance, osmoprotectant accumulation, exopolysaccharide production, and activation of antioxidant defense systems. Furthermore, PGPR substantially contribute to soil health by improving soil aggregation, enhancing microbial biodiversity, stimulating nutrient cycling, increasing soil enzyme activities, and improving nutrient-use efficiency in saline soils. Quantitatively, PGPR application has been reported to increase soybean growth and productivity by approximately 15–45% under saline conditions while reducing salt-induced physiological damage. These findings highlight the strong potential of PGPR as a sustainable long-term strategy for saline land management to restore soil health, strengthen climate resilience, and enhance soybean productivity.