The study area has a typical arid continental climate that is very cold in winter with little snowfall and very dry in summer with little rainfall. Local climatic characteristics have been described in our previous report (Zhao et al., 2016). The groundwater table varied from 1.2 to 2.6 m, with a salt concentration of 1.5–1.8 g L_1. The experimental soil was silty loam with a pH of 8.8 and contained 11.1 g kg_1 organic matter, 35.6 mg kg_1 available N, 6.4 mg kg_1 available P and 161 mg kg_1 available K at the 0–10 cm layer.