Experimental setup
The soil samples were air-dried and sieved through a 2-mm screen to remove roots, stones, and debris. The HS was then evenly loaded into three cylindrical polymethyl methacrylate (PMMA) boxes (diameter 20 cm, height 100 cm) to an SBD of 1.367g/cm3, and the W-RS was evenly loaded into three PMMA boxes with the same structure and size to an SBD of 0.874 g/cm3. To reduce the influence of soil air resistance on the water infiltration process, small holes of diameter 1 cm were opened on one side of the soil column at intervals of 5 cm for soil exhaust. The initial soil water content\(\ \theta\) (ISWC) of the HS was set to 4%, 8%, and 12% in the three samples, respectively, and that of the W-RS was set to 4.7%, 6.2%, and 9.6%, respectively.\(\ \)