2.1 Study site description
This study was conducted at the agrometeorological experimental station of Nanjing University of Information Science and Technology, Jiangsu Province, China (32.16° N, 118.86° E). This site was located in a subtropical monsoon climate zone, with average annual temperature 15.6ºC and average annual rainfall of 1100 mm. The average sunshine hours exceed 1900 hours, and the frost-free period was 237 days. The soil was silty loam texture with the content of sand, silt and clay of 5.3%, 85.2% and 9.5% in tillage soil (0-20 cm). The basic properties of the tillage soil: pH (H2O) 6.1, bulk density 1.51 g cm-3, soil organic carbon 8.8 g kg-1, and total nitrogen 1.2 g kg-1.