The Effects of Biochar on Soil Quality and Potato Yield in Arid and Semi-Arid Regions.

Aims To evaluate the effects of biochar produced at different pyrolysis temperatures on soil quality and its regulatory factors, and to elucidate the relationship between soil quality and potato yield, thereby identifying the optimal pyrolysis temperature and application rate. Methods A two-year field experiment (2023–2024) was conducted in North China to investigate the impact of different biochar pyrolysis temperatures (T1: 300°C, T2: 500°C, T3: 700°C) and application rates (C1: 10 t·ha⁻¹, C2: 20 t·ha⁻¹, C3: 30 t·ha⁻¹) on soil quality and its synergistic effect on potato yield. Results 1) Biochar application effectively alleviated soil compaction and significantly increased soil aggregation; 2) The C2T2 treatment significantly improved soil moisture content (θ _v ), organic carbon(SOC), available phosphorus(P), available potassium(K), total nitrogen(TN), microbial biomass carbon(MBC) and nitrogen(MBN), while reducing soil nitrate nitrogen(NO ₃ ^– –N) content; 3) The soil quality index (SQI) calculated using a nonlinear scoring model more accurately evaluated soil quality, with the SQI of C2T2 treatment increasing by 1.08–1.30 times compared to other treatments over two years. Potato yield increased linearly with the SQI; 4) Structural equation modeling indicated that biochar application promoted potato yield by improving soil moisture and nutrients (such as SOC, NO ₃ ^– –N, P, k, MBC, and MBN). Conclusions A soil quality evaluation method is developed for sandy loam soils in arid regions. The suitable biochar application is beneficial for SQI and potato yield improvement by optimizing soil moisture and nutrients.