All treatments in each site were randomized in the first year and the plot received the same treatment in the following years at all four study sites. The treatment plot size was
200m2 (20m×10m),400m2 (25m×16m),196m2 (14m×14m), and 200m2 (20m×10m) at Changping, Zhengzhou, Yangling, and
Qiyang sites, respectively. To avoid edge effects, the treatment plots were separated by 100-cm deep concrete barriers at all sites.