2.1 Study site
We conducted a continuous field experiment from 2003 to 2019 at a Dryland Farming Experimental Station in Shouyang (112-113°E, 37-38°N), Shanxi Province in northern China. The climate of the station is continental monsoon and its average annual potential precipitation and evaporation is 484 mm and 1750 mm, respectively (Wang et al. , 2019). The annual frost-free season lasts on average 131 days. The sandy loam cinnamon soil in experimental site was classified as Calcaric-Fluvic Cambisols (Li et al. , 2020). Table 1 shows soil chemical and physical properties initially.