Electrical resistivity tomography for spatiotemporal variations of soil moisture in a precision irrigation experiment

Soil moisture temporal variations play a key role in the hydrological processes occurring in the unsaturated zone, which are critical for annual crop yields. The electrical resistivity tomography technique was applied in a field cultivated with cotton in northern Greece, thereby investigating its potential to serve as a reliable soil moisture-monitoring tool for precision irrigation in highly heterogeneous, clay-rich soils. Repeated surface resistivity measurements were made along two plant lines combined with soil water content measurements conducted with a reference gravimetric method and an electromagnetic sensor. Resistivity pseudo-sections were inverted to produce 2D resistivity models, and time-lapse inversion algorithms were also used, to better calculate the temporal changes in subsurface soil resistivity. The results showed clear spatial and temporal changes in resistivity transects in accordance with rainfall/irrigation and dry periods. The soil resistivity data exhibited a power model relationship with gravimetric soil moisture point measurements and a fair correlation with electromagnetic sensor profiles.