Simulation of the landform change process on a purple soil slope due to tillage erosion and water erosion using UAV technology

Abstract

Both tillage erosion and water erosion are severe erosional forms that occur widely on sloping agricultural land. However, previous studies have rarely considered the process of landform change due to continuous simulation experiments of alternating tillage erosion and water erosion. To identify such changes, we applied a scouring experiment (at a 60 L min−1 water discharge rate based on precipitation data from the local meteorological station and the catchment area in the Yuanmou County, Yunnan Province, China) and a series of simulated tillage experiments where plots were consecutively tilled 5, 10, and 15 times in rotation (representing 5 yr, 10 yr, and 15 yr of tillage) at slope gradients of 5°, 10°, and 20°. Close-range photogrammetry (CRP) employing an unmanned aerial vehicle (UAV) and a real-time kinematic global positioning system (RTK-GPS) was used to measure landform changes, and high-resolution digital elevation models (DEMs) were generated to calculate net soil loss volumes. Additionally, the CRP was determined to be accurate and applicable through the use of erosion pins. The average tillage erosion rates were 69.85, 131.45, and 155.34 t·hm−2·tillage pass−1, and the average water erosion rates were 1892.52, 2961.76, and 4405.93 t·hm−2·h−1 for the 5°, 10°, and 20° sloping farmland plots, respectively. The water erosion rates increased as tillage intensity increased, indicating that tillage erosion accelerates water erosion. Following these intensive tillage treatments, slope gradients gradually decreased, while the trend in slope gradients increased in runoff plots at the conclusion of the scouring experiment. Compared to the original plots (prior to our experiments), interactions between tillage and water erosion caused no obvious change in the landform structure of the runoff plots, while the height of all the runoff plots decreased. Our findings showed that both tillage erosion and water erosion caused a pseudo-steady-state landform evolutionary mechanism and resulted in thin soil layers on cultivated land composed of purple soil in China.