Effects of tillage practices on water storage and soil conservation in red soil slope farmland in Southern China.

Under the current conditions of global climate change, many unreasonable tillage practices exacerbate soil erosion and seasonal drought in agriculture. The red soil slope farmland makes up a significant portion of agricultural land in southern China. It is crucial to enhance the water storage and soil conservation effects (WSE) by adopting appropriate agronomic practices on the red soil slope farmland, which ensures regional agriculture's sustainable development. Therefore, this study employed a combination of experimental plot positioning observations and artificially simulated rainfall experiments to analyze the WSE of four tillage practices: Conventional tillage (CT), Downslope ridge tillage (DT), Cross-slope ridge tillage (RT), and Plastic Mulching (PM). This study proposed the optimal tillage practices based on a comprehensive evaluation of their effects. The results indicate that there is a significant interaction (p < 0.05) between tillage practices and growth stages on soil water retention and infiltration characteristics. Under the same growth stage conditions, PM can reduce soil bulk density by 0.03-14.29% (p < 0.05) and increase temperature, soil moisture content, and total porosity by 4.00-6.67%, 0.68-18.23%, and 1.30-13.47% (p < 0.05), respectively, demonstrating the best water retention capabilities among the four tillage practices. However, during the rainfall-runoff process, the surface runoff amount (SRA) generated by PM and DT accounts for 68.15% and 90.83% of the total runoff, respectively, which is detrimental to soil water infiltration during rainfall. Both practices exhibit poor resistance to soil erosion and demonstrate low water storage and soil conservation effect index (WSEI) values of 0.38 and 0.33, respectively. Secondly, RT's SRA constitutes only 9.42% of the total runoff, which is beneficial for increasing the cumulative soil water infiltration amount (CIA) during rainfall. Among the three tillage practices, namely RT, DT, and CT, RT demonstrates strong soil water retention capabilities. It can significantly reduce the kinetic energy of soil erosion, enhance soil erosion resistance, and exhibit the highest WSEI of 0.84. Furthermore, CT exhibits a moderate WSEI of 0.75. In summary, from the perspective of WSEI, RT is the tillage practice that should be prioritized for promotion in the cultivation process of red soil slope farmland. Our research results can provide a scientific basis for constructing optimal tillage mode and improving the WSE of southern China's red soil slope farmland.