Objectives This study aimed to summarize and synthesize the effects of multi-site amendment experiments across different regions, thereby providing technical support for the comprehensive reclamation and sustainable utilization of saline-alkali lands in China.

Methods Using the keywords “saline-alkali”, “amendment”, “gypsum”, “biochar”, “organic fertilizer”, “organic acid”, “biological agents”, and “biogas slurry”, we searched the literature published from January 1995 to June 2025 in the CNKI, Wanfang, and Web of Science databases. A total of 1,238 observations were obtained from 165 publications. A meta-analysis was conducted to quantify the effects of ten amendment types on crop yield, soil pH, exchangeable sodium percentage (ESP), electrical conductivity (EC), total salinity, and soil organic matter (SOM) in the four major saline-alkali regions of China: the northwestern arid saline-alkali region, the upper-middle Yellow River saline-alkali region, the northeastern soda saline-alkali region, and the eastern coastal saline-alkali region. A comprehensive soil quality index (SQI) was calculated to compare soil quality changes induced by various amendments.

Results In the northwestern arid saline-alkali region, applying gypsum, organic fertilizer, and biological agents significantly increased cotton yield by 32.4%, 32.0%, and 30.5%, respectively. In the upper-middle Yellow River saline-alkali region, mixed amendments significantly increased corn yield by 88.7%. In the northeastern soda saline-alkali region, aluminum sulfate and mixed amendments enhanced rice yield by 177% and 107%, respectively. In the eastern coastal saline-alkali region, corn yield increased by 17.6% following mixed amendments and by 17.1% after applying biological agents. Organic fertilizer and biological agents had the best yield effects in the northwestern arid saline-alkali region; biochar had the highest yield effect size in the northeastern soda saline-alkali region; mixed amendments had greater yield effect sizes in the upper-middle Yellow River and northeastern soda saline-alkali regions than in the northwestern arid and eastern coastal saline-alkali regions. Gypsum and solid organic fertilizer had limited yield-increasing effects in the eastern coastal saline-alkali region, and biological agents were less effective in increasing crop yield in the northeastern soda saline-alkali region. The responses of soil chemical properties to various amendments differed among the four major saline-alkali regions, but similar trends were observed, with decreases in pH, EC, ESP, and total salinity and an increase in SOM. Random forest analysis identified soil salinity and ESP as the most critical soil factors regulating crop yield in the northwestern arid, upper-middle Yellow River, and northeastern soda saline-alkali regions, while EC and ESP were the dominant drivers of corn yield in the eastern coastal saline-alkali region. The top two amendments with the highest SQI values were mixed amendments and biological agents in the northwestern arid saline-alkali region, mixed amendments and gypsum in the upper-middle Yellow River saline-alkali region, organic fertilizer and biochar in the northeastern soda saline-alkali region, and biological agents and mixed amendments in the eastern coastal saline-alkali region, respectively.

Conclusions Considering region-specific yield responses, cross-regional yield performance of specific amendments, and soil quality indices, we identified the most suitable amendment strategies for each major saline-alkali region: 30 t/hm² gypsum and 16 t/hm² organic fertilizer for the northwestern arid saline-alkali region; mixed amendments (4.5 t/hm² gypsum+15 t/hm² biochar) or 15 t/hm² gypsum for the upper-middle Yellow River saline-alkali region; 300 kg/hm² aluminum sulfate and 16 t/hm² biochar for the northeastern soda saline-alkali region; and 200 L/hm² biological agents and mixed amendments (75 L/hm² biological agents + 15 t/hm² organic fertilizer) for the eastern coastal saline-alkali region.