Using a soil quality index to evaluate the artificial soil quality response to rehabilitation time

External-soil spray seeding (ESSS) supplies nutrients and water to plants, soils play a pivotal role in the successful rehabilitation of rock-cut slopes. However, few studies have explored how to accurately evaluate the artificial soil quality response to rehabilitation time to determine the effectiveness of the ESSS technique. In this study, taking the rock-cut slopes of Suining Railway Station to study, various soil samples were obtained from 20-year-old, 13-year-old and 9-year-old rehabilitation slopes, where we sampled the surface soil in north- and south-facing slopes, respectively. Fifteen soil indicators were measured as potential indicators of artificial soil quality, and the indicators with significant differences between rehabilitation time considered as a total data set (TDS). Principal component analysis (PCA) and correlation matrix analysis (CMA) were used to determine a minimum data set (MDS), and these indicators within MDS were integrated into a soil quality index (SQI) by standardized scoring functions (SSF) and weighted-additive methods. Results suggested that (1) the SQI was an effective tool for evaluating artificial soil quality, (2) the longer rehabilitation time, the higher artificial soil quality, and (3) the SQI of the north-facing slopes was higher than that of the south-facing slopes in the same rehabilitation years. Nevertheless, all rehabilitation slopes had a low SQI (SQI ≤ 0.560). Overall, ESSS is a technology that can effectively promote the ecological restoration of rock-cut slopes, but there still exist a room for improvement. In the future ecological reconstruction of rock-cut slopes, more attention should be paid to the restoration of soil quality on the south-facing slopes.