Temporal variations in runoff and sediment yield associated with soil surface roughness under different rainfall patterns

Soil surface roughness (SSR) is one of the topographic factors affecting soil erosion. Currently, temporal variation characteristics of runoff and sediment yield of SSR is still unknown. In this study, ridge tillage (RT) and linear slope (CK) were used to simulate different SSR. Artificial rainfall experiments including increased and decreased rainfall series were conducted in two runoff plots on a slope gradient of 15 degrees. The rainfall intensities were 1.0, 1.5 and 2.0 mm min(-1 )and the rainfall duration were 60, 40 and 30 min, respectively. A method combining of the pin meter and photography was used to measure microtopographic changes before and after each run. The results showed that the SSR values of RT ranged from 175.94 mm to 181.50 mm and SSR values of CK ranged from 75.66 mm to 79.80 mm. The temporal variations of runoff and sediment yield associated with SSR had positive long-range correlation and varied periodically every 9-16 min under different rainfall patterns. There was a critical value on the spatial heterogeneity of SSR that affecting soil erosion. SSR reduced the frequency of periodic oscillations of runoff and sediment yield, and then reduced the turbulence of runoff and sediment yield during the rainfall, which had good effect of soil and water conservation. When SSR exceeded the certain critical condition, SSR served as the source of erosion by increasing the periodic oscillation energy, increased the turbulence of runoff and sediment yield, which led to a large amount of soil and water loss. The findings will help elucidate soil erosion mechanisms in sloping farmland and provide a new insight for understanding of temporal variations in runoff and sediment yield. (C) 2019 Elsevier B.V. All rights reserved.