Raindrop energy and distribution above/below the canopy of seedling corn
As shown in Tables 1 and 2, the energy and size distribution of raindrops were significantly different between above and below the canopy of seedling corn. For the two rainfall intensities, the canopy mitigation of raindrop energy was observed more in conservation than conventional tillage measures. The percentage of raindrops with less than 2.5 mm diameter decreased when the raindrops larger than 2.5 mm diameter decreased at the rainfall intensity of 50 mm h-1, whereas the percentage of raindrops with less than 2.0 mm diameter decreased when that of raindrops larger than 2.0 mm diameter increased at the rainfall intensity of 100 mm/h.
Runoff-yielding time and runoffvelocity
Table 3 shows that conservation tillage measures could significantly delay the runoff-yielding time and decrease surface flow velocity, compared to CK and Vr, at the maize seedling stage. Compared with CK and Vr, the runoff-yielding times of the Cm, Hr, Hr+Cm, and Vr+Cm treatments were significantly postponed; the runoff-yielding time advanced at 100 mm h-1 than at 50-mm h-1. The Hr+Cm treatment successfully prevented runoff yielding throughout the rainfall event under 50 mm h-1, and the averagely prolonged runoff-yielding time was approximately 26.1 min, which was 23.8 times longer than that of the CK treatment under 100 mm h-1. The average delay time durations for other treatments from long to short were 23.6 min for Hr, 5.6 min for Cm, and 2.8 min for Vr+Cm.
Table 3 also shows that the declining effects on surface flow velocity were more obvious under light than under heavy rainfall intensity conditions. Compared to CK, the Hr+Cm, Cm, Vr+Cm, and Hr treatments significantly reduced the surface flow velocity, with a decline of 100% (no runoff generation), 75.8%, 71.9%, and 83.5%, respectively, at the rainfall intensity of 50 mm h-1 and 96.4%, 82.9%, 77.7%, and 71.5%, respectively, at the rainfall intensity of 100 mm h-1. However, Vr significantly increased the runoff velocity by 50.3% and 10.1% at the rainfall intensities of 50 and 100 mm h-1, respectively.
Total runoff and soil loss