2.2. Rainfall simulation and soil photographing
On the morning of April 10 2013, the big plastic sheets were removed from all 27 plots. Tap water was dyed with Brilliant Blue FCF at a concentration 3.0 g L−1 (Boll et al., 1992 and Flury et al., 1994). The dyed water was then showered at 10 mm min−1 onto the 27 plots one by one using a Meyer style rainfall simulator (Meyer and Harmon, 1984). The sprinkling pipe of the rainfall simulator was 3 m long, installed horizontally 2 m above the ground. Swiveling back and forth, the sprinkling pipe watered a scope of 3 m × 3 m within each plot. The rainfall intensity of 10 mm min−1 is much greater than that usually occurs in the area; however, it is the lowest intensity that could be achieved with the simulator. Applying simulated rain, all of 27 plots (including the FMRF treatment) were immediately covered with big plastic sheets to prevent soil water evaporation.