The enhancement of soil erosion resistance via soil and water conservation practices is a necessary venture in the modern agricultural industry. Soil infiltration performance, as a necessary indicator of erosion resistance, is closely related to soil aggregates. However, the relationship between the C/N ratio of soil aggregates and soil infiltration and the overall performance under conservation tillage practices is unclear. Experiments were conducted in 2022 and 2023 to observe the relationship between the soil carbon and nitrogen distribution patterns and soil infiltration of sloping cultivated land under different tillage practices. In this study, ridge tillage and pitting field + subsoiling tillage (RF-S) and contour tillage + subsoiling tillage (TP-S) have been used in a plot experiment, with down-slope cultivation (CK) as the control. The results showed that the stability of soil aggregates, the organic carbon and the total nitrogen contents of soil aggregates of different particle-sizes, and the overall soil infiltration performance were greatly increased under the RF-S and TP-S treatments (up-slope, mid-slope, and down-slope). Compared with CK, RF-S and TP-S significantly improved the stability of soil aggregates at different slope positions (on, in, and under the slope) and the C/N ratio and soil infiltration performance of aggregates with particle sizes of >2 mm and 2–0.25 mm. However, TP-S more effectively reduced the deposition of soil macroaggregates down the slope and can comprehensively improve the stability of soil aggregates and the infiltration performance. The mean weight diameter (MWD) and mean geometric mean diameter (GMD) of soil aggregates can reflect the distribution and stability of soil aggregates and also indicate the stability of soil structure. Compared with CK, the MWD of TP-S soil aggregates increased by 6% to 17.7%, the GMD increased by 9.7% to 27.2%, the average soil infiltration rate increased by 41.8% to 78.3%, the initial infiltration rate increased by 19.1% to 46.6%, and the stable infiltration rate increased by 109.2% to 165.9%. Soil infiltration performance is positively correlated with the C/N ratio of aggregates with particle sizes of >2 mm and 2–0.25 mm and negatively correlated with the C/N ratio of aggregates with particle sizes of <0.25 mm. The results of this study show that reasonable tillage measures are helpful in improving soil water and soil conservation and anti-erosion ability and illustrate the influence mechanism of soil aggregates on soil infiltration performance.
