Regulatory effects of phosphogypsum application on soil quality and plant physiology: A global meta-analysis

Phosphogypsum (PG), a bulk solid by-product produced from wet phosphoric acid manufacturing, can be used as a soil amendment after harmless and functional modification in agricultural production. This greatly reduces the environmental and land pressure stemming from PG stockpiles but also conforms to the development of resource recycling and green agriculture. However, how PG application methods (alone or combined) and dosage gradients affect soil physicochemical properties, plant physiology, and microbial community structure has not been systematically or quantitatively assessed, limiting its precise and standardized use across diverse ecological regions and farming systems. Based on a strict screening of 44 global empirical studies, we conducted a multi-dimensional meta-analysis to systematically quantify the effects of PG application on soil quality, crop growth, enzyme activity, and soil microbial diversity. The results showed that the application of PG alone significantly improved soil fertility by increasing soil organic matter (+27.5%), field water holding capacity (+38.0%), available phosphorus (+58.6%), alkali-hydrolysable nitrogen (+25.0%) and ammonium nitrogen (+26.0%), total potassium (+15.8%) and total nitrogen (+21.3%), while reducing soil pH by 12%. At the plant level, PG significantly promoted biomass accumulation (+22.9%), plant height growth (+18.9%), root length (+16.5%), and calcium enrichment in the aboveground (+126.1%). In terms of combined application, the use of PG in conjunction with biochar reversed the acidification, increasing soil pH by 14.9%. The combined application of PG and compound fertilizer showed significant synergistic effects: soil total potassium content increased by 86.5%, K⁺ and Ca²⁺ concentrations in plants increased by 112.3% and 147.9% respectively, Na⁺ content significantly decreased by 85.7%, and simultaneously achieved a significant increase in crop yield (+43.2%) and plant height (+35.3%). At the biological response level, PG significantly enhanced soil β-glucosidase (+6.6%) and urease (+20.4%) activities and increased chlorophyll content in plants (+20.3%). Meanwhile, it significantly activated the plant antioxidant system, with superoxide dismutase (SOD) and catalase (CAT) activities increasing by 15.6% and 42.6% respectively. However, a decrease of 18.2% in fungal community α-diversity (Chao1 index) was observed, suggesting the need to pay attention to the potential regulatory effects of long-term application on the structure of the soil microbial community. The sensitivity analysis of application dosage showed that the medium and low dosage range of 10%–50% (mass ratio) of PG application presented the best comprehensive benefits in most studies, which is conducive to expanding the soil nutrient pool and promoting the stable growth of crops. In conclusion, this study provides systematic scientific basis and practical parameter support for the agricultural resource utilization of phosphogypsum under the premise of ecological safety, and has important theoretical value and application significance for building a modern farmland ecosystem that is nutrient-efficient, environmentally friendly, and resiliently sustainable.