Objective This research was conducted to reveal the effects of biochar application on runoff generation and sediment yield in yellow soil slope of the Karst area.

Method Taking the yellow soil in the Southwest Karst as the research object, 4 biochar application rates (0%(CK), 1.25%(BC1), 2.5%(BC2), 5%(BC3)) and 3 slope levels (5°) , 15° and 25°), the effects of biochar application rates and slope gradient on the yellow soil slope erosion were studied under souring flow.

Result Compared with CK, the initial runoff time of the slope was reduced when the biochar application rates were 1.25% and 2.5%, while significantly increased in the application rate of 5%. With different slope gradients, the biochar addition significantly improved the soil infiltration capacity, reducing the total runoff by 3.05% to 13.32%. While the total sediment yield increased significantly, with an increase of 16.88 - 926.79 g h⁻¹. When the slope was 5°, the total sediment yield increased exponentially with the biochar application rates, and increased linearly at the slope of 15° and 25°. The runoff generation rates and sediment yield rates between different treatments reached a stable level at around 20 minutes. The runoff generation rates significantly decreased with the biochar application rates, especially at the slope of 25°, while the sediment yield rates increased.

Conclusion Adding biochar to the yellow soil slope farmland in Southwestern Karst areas can increase soil infiltration, reducing slope runoff, while increasing the rate and amount of sediment yield to a certain extent. The research results can provide a theoretical basis for the biochar application and the prevention and control of soil erosion in the yellow soil slope farmland of the Southwestern Karst area.