Phosphogypsum combined with yeast metabolites synergistically ameliorates saline-alkali soil and mitigates secondary salinization

Soil salinization threatens sustainable agriculture. In this study, a composite amendment combining phosphogypsum (PG) and yeast metabolites (Y) was prepared to remediate severe saline-alkali soils. Indoor culture and pot experiments were conducted to evaluate its efficacy. Results showed that the PY3 formulation (5% PG + 0.04% Y) was optimal, effectively neutralizing soil pH, reducing the exchangeable sodium percentage (ESP), and significantly increasing soil organic matter, cation exchange capacity, and key enzyme activities. High-throughput sequencing and structural equation modeling revealed that PY3 optimized the microbial community primarily by enhancing soil nutrient availability, while preventing the over-enrichment of Actinomycetes induced by PG alone. Pot experiments showed that PY3 mitigated secondary salinization from sole PG application, reduced leaf MDA content, modulated antioxidant enzyme activities, and improved photosynthetic efficiency, thereby alleviating physiological stress and improving photosynthetic efficiency, which in turn promoted crop biomass and nutrient accumulation. These findings suggest that the combined PG–Y amendment may hold potential for broader field-scale application in saline–alkali soil improvement. PY3 also enriched beneficial rhizosphere bacteria ( Proteobacteria , Firmicutes , and Bacillus ), accelerating nutrient cycling. In summary, under laboratory conditions, the composite amendment synergistically improved soil physicochemical properties, optimized the rhizosphere bacterial community, and promoted plant growth in severely saline–alkali soil, offering a promising conceptual basis for saline–alkali soil remediation. As the present evidence derives from short-term incubation and pot experiments with an exploratory 5% PG dosage, field-scale validation and dosage optimization remain necessary for practical application.