Effects of biochar from different pyrolysis temperatures on soil physical properties and hydraulic characteristics in potato farmland of arid and semi-arid regions

Biochar application is a promising method for improving soil quality; however, the effects of biochar produced at different pyrolysis temperatures on soil physical properties and hydraulic characteristics in arid and semi-arid regions remain unclear. Therefore, a two-year (2023–2024) field experiment was conducted in the northern Yinshan region of China to evaluate the impacts of biochar pyrolysis temperatures (T1: 300 °C, low; T2: 500 °C, medium; T3: 700 °C, high) and application levels (C1: 10 t ha⁻¹, low; C2: 20 t ha⁻¹, medium; C3: 30 t ha⁻¹, high) on soil physical properties, hydraulic characteristics, and their relationship with potato yield. Results indicated that: (1) Compared to the control (CK), the application of biochar significantly reduced soil bulk density, increased soil porosity, and improved the mean weight diameter (MWD) of soil aggregates and the content of water-stable aggregates larger than 0.25 mm (WR0.25); (2) The application of biochar significantly enhanced soil hydraulic characteristics (saturated water content (θs), field capacity (FC), plant available water (PAW), soil moisture content, and soil water storage) and yield. All hydraulic characteristics and potato yield exhibited a generally downward-opening parabolic trend with increased biochar pyrolysis temperature and application rate. Among these, biochar produced at a medium pyrolysis temperature of 500 °C at an application rate of 20 t ha-1 was optimal, resulting in a 27.15 % increase in potato yield compared to the control (CK); (3) Pearson correlation analysis and PCA showed that biochar application promoted potato yield by improving soil hydraulic performance, with hydraulic characteristics being the primary factor influencing potato yield. To enhance potato farmland's physical and hydraulic properties, we recommend a pyrolysis temperature of 500 °C and an application rate of 20 t ha⁻¹ as the optimal biochar model. This study provides a theoretical basis for using biochar to improve soil quality and enhance crop yield in arid and semi-arid regions.