2.1. Soil sample preparation
Soil samples (0–20 cm) were collected from Hetao Basin, Inner Mongolia Autonomous Region which is along with the Yellow River in China (latitude 40.719-41.1841N, longitude 107.278-108.7599E) (Fig. 1). The main soil textures are loam, sandy loam, and silt sand (Xue & Ren, 2017). There is a typical continental arid/semi-arid climate in the area.