Optimizing soil conditioner selection based on acidification severity for fertility and yield enhancement in southern...

Soil acidification is one of the main limiting factors affecting agricultural development in southern China. The application of soil conditioners, including lime, biochar, and organic fertilizer, has proven effective in ameliorating acidic soils. However, comprehensive evaluation of the effects of these conditioners on soil acidity, fertility, and crop yield across southern China remains scarce. In this study, we collated 477 observations from 110 publications to explore the effects of conditioners on soil acidity and crop yields, considering the influence of various regulating factors. The results showed that lime had the most significant impact on increasing soil pH and crop yield, with respective increases of 15.21% and 20.86%. Organic fertilizer significantly enhanced soil fertility, particularly soil organic matter, available nitrogen, available phosphorus, and available potassium, with increases exceeding 18%. The combined application of conditioners generally yielded superior results compared to individual treatments. As the duration of conditioner application increased, the acid-reducing effect gradually weakened, whereas soil fertility and crop yields continued to increase. Conditioner application was more effective in dryland areas than in paddy fields, and the crop rotation pattern further contributed to increase crop yields. Among various crop types, vegetables exhibited the highest yield increase, reaching 25.01%. The effect of reducing soil acidity was most pronounced when the initial soil pH was <4.5, resulting in a 20.28% increase in pH and a 97.95% reduction in exchangeable acidity. Crop yield increases were more significant when the initial pH was <5.5, with a rise of 20.00%. When the initial pH was >5.5, it was more conducive to enhancing soil fertility. Overall, soil improvement effects were more remarkable in soils with low initial organic matter content. Considering the effects of soil improvement on soil acidity, fertility, and crop yield, the application of a mixture of lime and organic fertilizer, biochar alone, and organic fertilizer alone seems most appropriate for acidic soil with an initial pH range of <4.5, 4.5∼5.5, and >5.5, respectively. In summary, the effectiveness of soil improvement is influenced by the type of soil conditioner, application rate and duration, land use pattern, initial soil properties, cultivation system, and crop type. Therefore, the remediation of acidic soils requires graded and categorized management strategies to achieve multiple objectives: "enhancing quality", "improving efficiency", and "reducing costs".