Objectives This study aims to evaluate the efficacy of biochar, lime, and organic fertilizer in ameliorating soil acidification and to elucidate the interplay among climate, soil properties, and management practices. The findings are expected to provide a scientific basis for developing region-specific remediation strategies.

Methods Based on keywords including “soil amendment or lime or biochar or organic fertilizer” and “soil pH or acidification or yield”, we searched for publications from 2000 to 2024 across Google Scholar, Web of Science, and the CNKI database. The selection process applied the following criteria: field experiments; staple food crops (rice, wheat, maize); application of soil acid amendments; reported outcomes on soil pH change or crop yield; availability of nitrogen application rate; and nitrogen content in organic fertilizers. A total of 749 articles were selected, yielding 1425 sets of soil pH data, 1802 sets of crop yield data, and 748 sets of the partial factor productivity of nitrogen (PFPN) data. Data on climate and soil properties were also extracted. A meta-analysis was performed to quantify the effects of the three soil amendments on soil pH, crop yield, and PFPN. Subgroup and correlation analyses were conducted to evaluate how climatic and soil factors influence amendment efficacy, with the goal of identifying suitable application conditions for each amendment type.

Results  Globally, the application of soil amendments significantly improved soil pH, grain yield, and PFPN. Lime application increased these parameters by an average of 14.30%, 29.34%, and 44.00%, respectively. Biochar resulted in increases of 4.20%, 12.13%, and 8.48%, while organic fertilizer led to gains of 3.70%, 24.17%, and 6.34%. Subgroup analysis revealed that lime was most effective in coarsely-textured, strongly acidic soils (pH≤5.5) under a mean annual temperature (MAT) > 16℃ and initial organic carbon content < 12 g/kg. Biochar performed optimally in medium-textured, strongly acidic soils under MAT>16℃, while organic fertilizer was most beneficial in medium-textured, slightly acidic soils under MAT>16℃ and annual precipitation >1200 mm.

Conclusions  Lime, biochar, and organic fertilizer are all effective in mitigating soil acidification, increasing crop yield, and enhancing PFPN. Among them, lime exhibits the most rapid and pronounced effects, biochar provides the most consistent improvements, and organic fertilizer offers sustained yield regulation across the broadest application scenarios. Specifically, CaO-based lime, shell-derived biochar, and straw-based organic fertilizer were identified as the most effective forms within each category. For practical application, the selection, application rate, and duration of these amendments should be strategically adjusted based on initial soil acidity, soil organic carbon content, and local climate conditions, enabling scientifically informed and precise management of soil acidification.