Current applications and future prospects of microorganisms in the amelioration of saline-alkali soil

Saline-alkali land, as a significant reserve of arable land resources, is of strategic importance for ensuring global food security and addressing arable land shortages through its ecological restoration and efficient utilization. In recent years, microbial amendment technologies, due to their eco-friendliness and sustainability, have received considerable attention and have become a research hotspot in soil remediation. Microorganisms significantly improve the physicochemical properties of saline-alkali soil and promote crop growth through multiple mechanisms, including regulating the soil microenvironment, alleviating salt stress damage to plants, and enhancing soil nutrient utilisation efficiency, thus paving a new way for saline-alkali land management. This article reviews the current research progress in the microbial improvement of saline-alkali soil, including the diversity of microbial germplasm resources for improving saline-alkali soil, the mechanisms of action and application effects of strains, and the improvement of excellent strains. Existing studies have mined a wealth of microbial resources encompassing Bacillus, Pseudomonas, Streptomyces, Enterobacter, Trichoderma and arbuscular mycorrhizal fungi for the improvement of saline-alkali soil. Microorganisms improve the soil microecological environment through diverse mechanisms, regulate soil physicochemical properties, and inhibit the occurrence of plant diseases, thereby enhancing crop yields and fruit quality. Some microorganisms can neutralise alkaline substances in the soil by producing organic acids through metabolism to regulate soil pH and optimise the plant rhizosphere microenvironment. In addition, they can secrete phytohormones, degrade ethylene precursors, etc., to promote plant growth and development, synthesise extracellular polysaccharides, functional proteins and other secondary metabolites to improve soil aggregate structure and physicochemical properties, regulate the structural composition and diversity of soil microbial communities and secrete antimicrobial substances to inhibit the reproduction of plant pathogenic microorganisms and prevent and control soil-borne diseases, and improve plant stress resistance by regulating plant immune responses. The available studies mainly focuses on single strains, the field application of which is affected by the complex environment of saline-alkali land, demonstrating limited effects and insufficient stability. Furthermore, the technical system for microbial agent preparation, storage, and standardised application has not yet been perfected, and the interaction and regulation mechanisms among microorganisms, plants, and soil have not been fully clarified. In the future, focusing on the needs for biological improvement of saline-alkali land, multi-omics technology and genetic engineering methods can be combined to analyse the molecular mechanisms of microbial action, optimise efficient strain cultivation technology, and develop preparation and supporting application technologies for multifunctional compound microbial agents, and improve the industrialisation process system, thus providing theoretical support and technical guarantee for efficient biological improvement and sustainable utilisation of saline-alkali land from multiple dimensions.