To improve clayey soil structure and alleviate seasonal drought stress in the red soil region of south China, this study investigated the impacts of different tillage treatments on plough layer thickness, soil bulk density, moisture, nutrients and sweet potato yield. The tillage treatments included: conventional rotary tillage to 15 cm depth (RT) as a control, Fenlong tillage to 20 cm (FL20), 30 cm (FL30) and 40 cm (FL40) depths. The results showed, compared with RT, FL30 and FL40 treatments significantly increased the thickness of plough layer, reduced soil bulk density and enhanced saturated hydraulic conductivity. Felong tillage increased the rate, amount and depth of water infiltration, as consequently enhanced soil water storage which was greater in the dry season than in the wet season. Fenlong tillage further redistributed nutrients down to deep soil layer, causing “less content of nutrients in the surface layer but higher content in the deep layer”. Therefore, compared to RT, Fenlong tillage promoted sweet potato yield by 89%–117%. In conclusion, Fenlong tillage can remediate soil physical properties, redistribute soil nutrients in the plough layer, increase soil water storage, and then enhance crop yield significantly.