Effect of soil surface roughness on infiltration water, ponding and runoff on tilled soils under rainfall simulation experiments

Agriculture has a large effect on the properties of the soil and with that on soil hydrology. The partitioning of rainfall into infiltration and runoff is relevant to understand runoff generation, infiltration and soil erosion. Tillage manages soil surface properties and generates soil surface roughness (SSR) that affects the partitioning of the rainfall. The objective of this study was to quantify the amount of rainwater that infiltrates, is temporarily stored in surface depressions and flows out of the surfaces during rainfall events. A set of tillage-induced rough surfaces with slope steepness of 10° and 15° was used under simulated rainfall, and a smooth surface served as a control. Rainfall intensities were 60 and 120 mm h−1, and two soil erosion periods, overland flow erosion period (OFEP) and rill flow erosion period (RFEP), were monitored for each rainfall intensity. The results showed that for OFEP, infiltration water was 58% and 76% of the total rainwater on the rough surfaces and was approximately 1.5 and 2 times greater than that on the smooth surfaces for the different rainfall intensities. The surface runoff was consistently small for the OFEP but significantly increased for the RFEP. For example, for the RFEP, the amount of surface runoff was up to 78.66% of the total rainwater on the rough surfaces under rainfall of 120 mm h−1 in intensity. The amount of rainwater stored in surface depressions was significantly less than infiltration water and surface runoff for all conditions. The mean transformation ratio of rainwater into surface depression storage, infiltration water and surface runoff in the OFEP and RFEP was 0.07:0.49:0.44 for the rough surfaces and 0.01:0.29:0.70 for the smooth surfaces. For the tilled surfaces, more than 50% of rainwater was be harvested through tillage technique during a rainfall event, whereas for the smooth surfaces, only 29% of rainwater. Our result will be useful when evaluating the impact of tillage on soil moisture content and even studying soil erosion in agriculture land.