Application of Beneficial Microbes to Enhance Agronomic Performance and Soil Health in Problematic Soils: Mechanisms, Challenges and Climate-resilient Agricultural Systems
Problematic soils, including saline, drought-affected, nutrient-deficient, acidic, and heavy metal-contaminated soils, represent major constraints to global agricultural productivity and soil sustainability. These unfavourable soil conditions disrupt nutrient availability, microbial activity, water uptake, and plant physiological processes, ultimately reducing crop growth and yield. Furthermore, prolonged environmental stresses often contribute to diminishing microbial populations, reducing the abundance and activity of beneficial microorganisms involved in nutrient cycling, soil fertility, and plant stress adaptation. Consequently, microbial inoculation has emerged as a promising eco-friendly strategy for restoring soil biological functions and improving agronomic performance under stressful environmental conditions. This review aimed to evaluate the application of beneficial microbes in problematic soils through bibliometric and systematic literature review approaches. Bibliometric analysis using VOSviewer revealed increasing research trends related to rhizosphere microbiology, plant growth-promoting rhizobacteria (PGPR), microbial diversity, diminishing microbial populations, salinity stress, drought stress, and sustainable agriculture. The systematic review demonstrated that beneficial microbes, including PGPR, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, arbuscular mycorrhizal fungi (AMF), and microbial consortia, significantly improve plant growth, nutrient uptake, chlorophyll content, stress tolerance, and crop productivity under various problematic soil conditions. In addition, microbial inoculation enhances soil health through improved nutrient cycling, microbial activity, soil enzyme activities, soil aggregation, and remediation of salinity and heavy metal toxicity. Despite challenges related to field performance variability, limited microbial survival, environmental variability, and insufficient farmer awareness, beneficial microbes remain promising biological agents for supporting sustainable and climate-resilient agricultural systems while reducing dependence on synthetic agricultural inputs.