In many orchards, irrigation scheduling is designed based on data from meteorological networks and considering homogeneous soil properties. Such assumptions may result in inefcient irrigation, which is difcult to constrain without expensive or invasive techniques. Here we have evaluated the ability of the electrical resistivity tomography (ERT) for detecting meterscale irrigation uniformity and deep percolation during irrigation. The spatiotemporal variability of soil volumetric water content (VWC) in a vineyard located near Santiago (Chile) was inferred using ERT monitoring of two irrigation cycles. The electrical resistivity structure up to 4 m depth was estimated using two-dimensional inversion of ERT data.
ERT results were verifed by comparing resistivity models with VWC measured with soil moisture sensors, soil properties mapped in a 2 m-depth soil pit, and the spatiotemporal evolution of VWC obtained by solving numerically Richards equation. Largest temporal variations of resistivity were observed within the root depth (1 m) and are consistent with expected relative changes in VWC during irrigation. ERT images exhibit lateral changes in resistivity at these depths, likely indicating non-uniform infltration of water controlled by observed soil texture variations. Resistivity changes were also observed below the root zone, suggesting that a fraction of the irrigation water percolates downward. These fndings can be explained by an excess of irrigation water applied during the monitoring, which was planned considering regional evapotranspiration (ET) data that overestimated the actual ET measured at the vineyard. Altogether, our results suggest that ERT monitoring during irrigation is a cost-efective tool to constrain the performance of irrigation systems.