Objective Investigating the effects of lime and husk biochar combined application on the fertility of acidic red soil and peanut yield provided a theoretical basis for the dual improvement of red soil pH and peanut yield.

Method Through the field peanut experiment, using conventional fertilizer treatment as the control (CK), four combined application treatments were set: L1C1 (lime, 750 kg hm⁻²; husk biochar, 2250 kg hm⁻²), L1C2 (lime, 750 kg hm⁻²; husk biochar, 4500 kg hm⁻²), L2C1 (lime, 1500 kg hm⁻²; husk biochar, 2250 kg hm⁻²), and L2C2 (lime, 1500 kg hm⁻²; husk biochar, 4500 kg hm⁻²). Soil pH, organic matter, available nitrogen, phosphorus and potassium nutrient contents were determined on the 15^th day after sowing and after peanut harvesting, as well as peanut yield. Then, the relationship between the fertility of acidic red soil and peanut yield were explored under lime and husk biochar combined application.

Result Compared with CK, the soil pH, organic matter, available nitrogen, phosphorus, and potassium contents on the 15^th day after sowing in L1C1, L1C2, L2C1 and L2C2 treatments were increased by 0.15 - 0.32 units, 11.92% - 22.95%, 42.07% - 61.74%, 17.05% - 43.99%, and 13.72% - 31.68%, respectively, After peanut harvesting, the contents of soil pH, organic matter, available nitrogen, phosphorus, and potassium contents in L1C1, L1C2, L2C1 and L2C2 treatments also showed higher trends than those in CK. For the lime and husk biochar combined application treatments, and peanut yields were increased by 8.30% - 13.31%. The comparison of different combined application treatments showed that the L2C1 and L2C2 treatments significantly increased the soil pH and available nitrogen content after peanut harvesting compared to the L1C1 and L1C2 treatments under the same amount of husk biochar application. There was a significant positive correlation between soil pH and available nitrogen with peanut yield on the 15^th day after sowing and after harvesting. When soil pH increased 0.1 unit on the 15^th day after sowing, peanut yield increased 80.25 kg hm⁻², which was significantly higher than that of peanut harvesting (64.12 kg hm⁻²). However, when the soil available nitrogen increased by 1.00 mg kg⁻¹ on the 15^th day after sowing and after peanut harvesting, the increasing rates of peanut yield were similar (11.07 and 9.72 kg hm⁻²).

Conclusion Therefore, Compared with conventional fertilizer treatment, lime and husk biochar combined application can significantly increase the pH of acidified red soil, the contents of soil available nitrogen, phosphorus and potassium, and improve peanut yield. Moreover, it is suggested that soil pH and available nitrogen should be regulated in acid red soil for attaining high yield of peanut.