2.1 | Study site
The experimental site is located in the city of Sanyuan, Shaanxi province, in the southern Loess Plateau (34°36′N, 108°52′E). This region has a sub-humid, warm-temperate continental monsoon climate with a mean annual temperature and mean annual precipitationof12.9°C and 527 mm, respectively. The soil is termed as Lou soil (manural loess soil) and classified as Eum-Orthic Anthrosol (Udic Haplustalf in the USDA system). The basic soil properties (0–20 cm depth) are shown in Table 1.