Experimental design and procedures
Two tillage systems, conventional and conservation, were applied in this study. The two conventional tillage practices included flat-planting without ridges and mulching (control, CK) and vertical ridging without mulching (Vr). Four conservation tillage measures included flat-planting and mulching without ridges (Cm), horizontal ridging without mulching (Hr), horizontal ridging with mulching (Hr+Cm), and vertical ridging with mulching (Vr+Cm). All plots were randomly arranged (Figure 2).
In Northeast China, soil erosion is caused by two types of rainfall events: short-duration rainfall under high-intensity rainstorm and long-duration rainfall under low-intensity rain. In terms of rainstorm status, generally momentary rainfall intensities larger than 23.4 mm h−1 cause soil erosion with an approximate duration of 1 h in the region (Zhang et al., 1992). Thus, in this study, two rainfall intensities of 50- and 100-mm h−1 were used as representative rainfall intensities lasting for a period of 1 h.
All plots were subjected to a pre-rain at 30 mm h-1for 5 min to maintain consistent soil moisture, consolidate loose soil particles, and flatten the soil surface before 24 h of experiments (Shen et al., 2016). Before the experiment, the rainfall intensity was calibrated to ensure the achievement of target intensity and fulfillment of experimental requirements (uniformity >90%, Figure 3a) (Shen et al., 2016). After each rainfall, the plots were repaired for the next run via a process including drying, replacement and recovery of the topsoil layer and lost cornstalk, smashing of soil clods, restoration of broken ridges, and smoothing of irregularities on the surface (Polyakov & Nearing, 2003).