Effects of Contour Antislope Terracing on Preferential Soil Flow in Sloping Cropland in the Alpine Valley Area of Southwest China

This study was conducted to reveal the response relationship between soil preferential flow characteristics and soil pore structure of sloping cropland under contour antislope step measures in the alpine canyon area of Southwest China. In the sub-watershed of Nantangjing, Yunlong County, the upper and lower slopes of primary sloping cultivated land (PSC) and contour reverse-slope terraced rectified land (CR) were used for the study, and a field staining tracer test was used to compare the differences in preferential flow morphology between different slopes with and without measures. The maximum infiltration depth of preferential flow under the contour reverse-slope terrace land preparation reached 21 cm. The stained area ratio tended to decrease with increasing soil depth. Compared to the original slope farmland, the stable infiltration rate under land preparation increased from 0.017 to 0.244 cm3·s−1, and the maximum macroporosity increased by up to 17.00%. Furthermore, land preparation measures significantly enhanced the correlation between macropore quantity and preferential flow characteristics, with the highest correlation coefficient reaching 0.98. And the soil factors in total porosity, total nitrogen and organic matter were particularly influential on preferential flow. Contour antislope terracing promotes the formation and development of preferential soil flow by remodeling soil structure and optimizing pore network distribution.