Soil Aggregate Stability and Characteristics of Nitrogen, Phosphorus, and Potassium Contents in Cut Slope Soils With Different Aspects in Plateau Areas

Abstract

Slope aspects can affect the soil-forming process. The implementation of road construction projects in plateau regions has resulted in the formation of numerous cut slopes. However, the soil aggregate stability and the characteristics of soil nitrogen (N), phosphorus (P), and potassium (K) nutrients under different cut slope aspects (east-facing slope (EFS), west-facing slope (WFS), south-facing slope (SFS) and north-facing slope (NFS)) are still unclear. In this context, the present study aims to assess the characteristics and influencing factors of soil aggregate stability, as well as N, P, and K contents, under different slope aspects in typical cut slope soils with the four different aspects in the southwestern plateau of China. In addition, the relationships of the soil aggregate stability with the soil N, P, and K contents were further explored in this study. The results showed significant differences in the soil aggregate stability (MWD, mean weight diameter) between the four slope aspects. The MWD values of the WFS and SFS were 1.18 and 1.16, respectively, which were significantly higher than those of the EFS and NFS (p < 0.05). Large macroscopic aggregates (LMA) showed the greatest contribution to the MWD values. The soil total phosphorus (TP), total nitrogen (TN), total potassium (TK), alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), available potassium (AK), and soil organic carbon (SOC) contents showed significant differences between the four slope aspects and soil particle sizes. However, comparatively lower SOC contents were observed in the silt and clay fraction (SCA). The SOC contents and soil pH were the major factors influencing the LMA and SCA, which, in turn, affected the soil aggregate stability and contents of N, P, and K. The current study provides a useful reference for improving the quality of cut slope soils.