Biochar's dual impact on soil acidity management and crop yield enhancement in acidic soils: a meta-analysis

Background and aims: Biochar is a promising and widely used soil amendment to alleviate soil acidification and improve crop productivity. Quantitative analysis of the impact of biochar application on soil pH and crop yield can help promote its optimal utilization. Methods: We compiled 286 peer-reviewed articles, i.e., 224 articles on yield, 188 articles on soil pH to investigate the impact of biochar application on crop yield, soil pH and other physicochemical properties in acidic soils. Results: Application of biochar significantly increased soil pH and yield by 7% and 21%, respectively. The increase in soil pH exhibited a positive correlation with crop yield, and relationship varied among crop type. The most significant increase in soil pH and crop yield following biochar application was observed in strongly acidic soils (pH < 4.5) characterized by low CEC, < 5 cmol kg⁻¹, and low soil OM content, < 6 g kg⁻¹. Among soil physicochemical properties, biochar application had no significant impact on soil OM, increased soil CEC and CS by 27% and 23%, respectively, while reduced soil BD by 9%. Tropical region demonstrated the most significant increases in soil pH 9% and crop yield 35% following biochar application. Conclusion: Considering the implications of biochar on soil pH, soil properties, and crop yield, the incorporation of wood-derived biochar pyrolyzed at temperatures < 500 °C appears to be most suitable for acidic soils, particularly those with an initial pH < 4.5. Our findings can aid in optimizing management strategies for biochar application on acidic soils.