Synergistic effects of biochar-lime enhance acidic soil remediation and sustain peanut productivity under continuous cropping systems.

Soil acidification severely limits peanut productivity. Although lime and biochar can individually improve soil conditions, the effects are often short-lived. The combined effect of biochar and lime (BL) across multiple growing seasons remains unclear. This three-year field study investigated the synergy of biochar-lime co-application (BL) in remediating acidic soils and sustaining peanut yields under continuous cropping. BL was more effective than single amendments (BC/LM), operating through a dual mechanism: (1) Lime rapidly neutralized toxic aluminum (Ex-Al³⁺), while biochar helped retain Ca²⁺, prolonging the pH buffering effect and further reducing aluminum toxicity; (2) Biochar enriched soil microbial communities, which increased the activity of key enzymes involved in nutrient cycling (urease: +49.84%; phosphatase: +46.14%). This improved soil environment reduced oxidative stress in peanuts (MDA: -20.01%) and enhanced their antioxidant defense system (SOD: +27.46%; POD: +34.60%), leading to higher and more stable yields (+ 11.07-27.26% vs. CK) with less year-to-year variation (- 4.66% yield decline). Economically, the lasting effects of BL allowed for a 53% reduction in amendment inputs by the third year, resulting in a 22.91% higher net income than using lime alone. These results demonstrate that BL co-application is a promising strategy for managing acidic soils by simultaneously addressing chemical and biological constraints in continuous cropping systems.