Advances in Biological and Physical Salt-Reduction Technologies for Reclaiming Saline–Alkali Land: A Comprehensive Review with an Emphasis on China

Soil salinization affects more than 954 Mha of arable land globally, with approximately 10–20 Mha abandoned annually. Conventional engineering and chemical remediation suffer from high water demand, salt re-accumulation, and secondary pollution risks. While this review draws primarily on the extensive body of research from China—where saline–alkali land covers approximately 99.13 Mha—it also incorporates key international case studies for comparative analysis. The review synthesizes biological and physical technologies for saline–alkali land reclamation, identifies critical challenges, and proposes an integrated remediation framework. A systematic search of Web of Science, Scopus, and CNKI databases (2000–2026) yielded 2847 records, of which 41 studies formed the systematic evidence base for the five technology clusters and 41 were retained as background references following the PRISMA framework. Because the search included the Chinese CNKI database and China contains one of the world’s largest saline–alkali land areas, particular emphasis is placed on Chinese case studies, complemented by representative international examples. Data were extracted on technology type, salt removal efficiency, crop yield, and application stage, and synthesized through quantitative cross-technology comparison. Five dominant technical clusters were summarized: (i) gene-based breeding (CRISPR/Cas, MAS) achieving 20–28% yield gains on sodic soils; (ii) halophyte phytoremediation removing 83–91% of soil salts over three growing seasons; (iii) microbial inoculants improving crop salt tolerance by 15–35% under controlled experimental conditions; (iv) agronomic rotations and straw amendment reducing topsoil salinity by 30–50%; and (v) solar-driven interfacial evaporation achieving 91.4% salt removal in a single proof-of-concept field trial at a material cost of approximately USD 0.004 per straw unit. Integrated bio-physical deployment, however, remains at the experimental scale. Combining rapid physical desalination with long-term biological remediation represents a promising research direction that requires systematic field validation before practical deployment. Key knowledge gaps include the long-term edaphic consequences of solar desalination, field-scale reliability of microbial consortia, and absence of regionally validated integrated protocols. We propose a structured roadmap with explicit timelines and policy recommendations to accelerate translation from research to practice.