A horizontal mobile dielectric sensor to assess dynamic soil water content and flows: Direct measurements under drip irrigation compared with HYDRUS-2D model simulation

The HYDRUS-2D simulation software has been used for irrigation management. Its performance under realistic irrigation regimes requires evaluation with new methodologies that integrate larger soil volumes, because soil water content is highly variable in time, space and scale. We compare direct measurements in a sloping field environment under drip irrigation with simulation using HYDRUS-2D. An advanced mobile sensor technology is used to track the dynamics of soil water content, and thus of unsaturated flow, at 0.25 m and 0.50 m depth in a field plot (6 m x 3 m; 4 degrees slope) beneath two parallel (0.5 m separation; 7 emitters per delivery tube) dripper arrays. We document an asynchronous sequence of wetting fronts driven by the sloping surface and capture the field results well using HYDRUS-2D, in the spatial (R-2 = 0.935-0.963, p < 0.01, RMSE = 0.024-0.027 cm(3) cm (3)) and time (R-2 = 0.804-0.983, p < 0.01, RMSE = 0.9-1.8 h) domains. In general, the HYDRUS-2D simulation system has potentially excellent capability for characterizing temporal moisture redistribution, tracking wetting front dynamics and predicting the time required for volumetric soil water content (VSWC) to reach field capacity under drip irrigation. Moreover, our study showed that the mobile dielectric sensor is a powerful tool to monitor infiltration of drip array irrigation both in spatial and time domains. (C) 2018 IAgrE. Published by Elsevier Ltd. All rights reserved.