Abstract: The reclamation of coal mining subsidence area is one of the challenges in coal mining area. We examined the effects of different drip irrigation methods and biochar application rates on peanut yield in coal mining subsidence area. A split-plot design experiment was conducted with two irrigation methods (i.e., film-mulched drip irrigation (M) and shallow buried drip irrigation (Q)) as the primary plots, and three biochar application rates (0 (B₀), 10 (B₁₀), and 20 t·hm^-2 (B₂₀)) as the subplots in 2021 and 2022. Root growth, dry matter, nitrogen accumulation in dry matter, yield and yield components, and soil inorganic nitrogen content were measured. Compared with the shallow buried drip irrigation, the film-mulched drip irrigation significantly increased root length, root volume, root surface area, dry matter accumulation at pod filling stage, 100-kernel mass, 100-fruit mass, and pod yield, but decreased soil NH₄⁺-N and NO₃^--N contents. Pod yield, 100-kernel mass, and 100-fruit mass under the film-mulched drip irrigation were 14.9%, 8.9%, and 6.3% higher than those under the shallow buried drip irrigation, respectively. Root length (except at the seedling stage), root volume (except at the seedling and pod setting stages), root surface area (except at the seedling stage), dry matter accumulation at the pod filling stage, 100-fruit mass, 100-kernel mass, and grain yield initially increased and then decreased with increasing biochar application rates. The peak values were observed under the B₁₀ treatment, the pod yield under which was 19.8% higher than under the B₀ treatment. Soil NH₄⁺-N content (except at the seedling stage) decreased while soil NO₃^--N content (except the seedling stage) and plant N accumulation increased with increasing biochar application rates. Under MB10 treatment, root length, root volume (except at pod setting stage), root surface area (except at seedling stage), dry matter accumulation at pod filling stage, 100-fruit mass, 100-kernel mass and yield were all optimal, with the yield being 38.8% higher than that under QB0 treatment. Peanut yield, 100-kernel mass, and 100-fruit mass had a significant and positive correlation with total root length and root surface area. The 100-fruit mass was significantly and positively correlated with soil NH₄⁺-N and NO₃^--N contents. In conclusion, the application of 10 t·hm^-2 biochar combined with film-mulched drip irrigation promoted root growth of peanut, improved plant inorganic nitrogen absorption, increased dry matter accumulation, and finally increased yield. Our findings would provide technical support and theoretical reference for land reclamation in coal mining subsidence areas.

Key words: peanut, film-mulched drip irrigation, biochar, coal mining subsidence area, yield