Objective The effects of different modified materials on the acidification characteristics of strongly acidic yellow soil were explored, and the best combination of different modifiers was selected to provide theoretical and technical support for the improvement of acidified yellow soil.

Method The indoor short-term soil culture experiment was carried out, and 11 treatments were set up, including CK (do not apply any modified materials), N (single application of nitrogen fertilizer), application of organic fertilizer and its combination with different amounts of biochar or dolomite powder. The variation characteristics of soil pH, exchangeable acid and exchangeable base ions were analyzed.

Result Compared with CK, the pH of N treatment was significantly increased by 0.46 units, the exchangeable acid was significantly increased by 8.63%. Compared with N treatment, the total amount of exchangeable base ions increased by 120.34%, the soil pH of organic fertilizer combined with biochar or dolomite powder was significantly increased by 0.15 - 0.82 units, the exchangeable acid decreased by 12.05% - 36.25%, and the total amount of exchangeable base ions increased by 228.84% - 500.57%. The treatment of organic fertilizer + high amount of biochar + high amount of dolomite powder had the best improvement effect. Soil pH was significantly negatively correlated with exchangeable acid, and the linear correlation with exchangeable hydrogen was higher. Soil pH was significantly positively correlated with exchangeable base ions, in which exchangeable calcium played a leading role. The alkalinity of the modified material was significantly positively correlated with pH and exchangeable base ions, and significantly negatively correlated with exchangeable acid. The correlation coefficients with exchangeable aluminum, exchangeable potassium and exchangeable calcium were higher.

Conclusion Soil acidification is closely related to the content of exchangeable acid and exchangeable salt ions, and is most affected by exchangeable calcium. The improvement effect of single application of organic fertilizer on strongly acidic soil was not good, and the combination of dolomite powder or biochar could significantly increase the improvement effect of acidification, and the combination of the two is the best.