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The independent effects of hedgerow or grass ditches on the migration of runoff, sediment and nutrients are well known; however, the effects of combined hedgerow–grass ditch systems have rarely been assessed. Vegetation stem diameter (VSD) is an essential variable that changes the effectiveness of a hedgerow–grass ditch system in reducing runoff and sediment yield on sloping lands. A hedgerow–grass ditch system was simulated to interpret the effects of varied VSDs i.e., 0 (control), 0.1, 0.2, 0.4 and 0.8 cm in hedgerow on runoff and sediment yield by laboratory rainfall simulation. Compared to the control, the time to runoff initiation presented a 43.3% delay in 0.8 cm VSD (p < 0.05), and the runoff rate was significantly reduced by 16.6% in the 0.2 cm VSD and by 17.0% in the 0.8 cm VSD, respectively (p < 0.05). The sediment yield rate decreased by 74.2% and 85.8% relative to that of the control, respectively (p < 0.05). The reduction was 5.3–17.0% for the runoff rate and 3.5–85.8% for the sediment yield rate with varied VSDs relative to the control. The sediment yield rate decreased remarkably as an exponential function with increased stem diameter (p < 0.05). Our results have great significance for creating strategies for soil and water conservation on sloping lands.
Song et al. (Thu,) studied this question.