Fenlong-ridging combined with composite modifier reconstructs soil microbiome to mitigate saline stress and enhance sustainable cultivation of Isatis indigotica Fortune.

Structural barriers and nutrient scarcity constrain medicinal plant cultivation in coastal saline soils. To address these challenges, we investigated a physical-chemical-microbial synergistic remediation strategy using Fenlong-ridging (FR) and a composite modifier (CM) by evaluating four soil treatments: conventional tillage; FR only; a CM only and FR combined with a CM (FR_CM). A comparative analysis of the four treatments revealed FR_CM to be the most influential strategy for improving coastal saline soil. The FR_CM treatment reduced soil electrical conductivity and bulk density by 78.38% and 29.31%, respectively; enhanced soil nutrient content and Isatis indigotica Fortune biomass by 68.91-114.29% and 126.52%, respectively; induced significant reorganization of microbial community structure at the phylum/OTU levels; elevated microbial network parameters, including positive/negative correlation ratios, modularity, and average path length; and enriched functional taxa such as fermentation and chitinolysis, while enhancing stress-tolerant phenotypes and suppressing potentially pathogenic phenotypes. This work establishes a theoretical foundation and technical paradigm for microbial-mediated remediation in saline-alkali ecosystems to assist crop-to-environment adaptation strategies and maintain sustainable medicinal plant production.