In soil science, a crucial role is played by the Soil-Plant continuum, as it is a major performer of the exchanges of mass and energy between soil and plants. However, despite its importance and its strong interconnection with human activity, the characterization of this subdomain is still in an early stage, mainly because of the lack of spatial and temporal information regarding the occurring processes. To overcome this issue, we present the combination of geophysical measurements and hydrological modeling in the framework of an hydrogeophysical approach, with the aim of characterizing the active root zone, i.e. the portion of the root system involved in the water uptake.
The water uptake is performed by root hair, the microscopic cell outgrowths whose location is difficult (if not impossible) also after the removal of the root system from the soil. Nevertheless, determining its position is fundamental not only for merely scientific purposes, but most of all for practical applications, as it affects the performing of precision irrigation. Therefore, in this work I propose the identification of the active root zone on the basis of its main effect, i.e. the reduction of soil water content over time. This is achieved by means of 3-D small-scale electrical resistivity tomography (ERT) carried out combining superficial and borehole electrodes. The datasets obtained provide interesting insights into the root system activity, given their abundance of information regarding both atmospheric and underground phenomena (i.e. transpiration and root water uptake, respectively). In particular, the ERT time-lapse approach well highlights the portions subject to a decrease in water content, which can be related to the water uptake put in place by the plants. Nevertheless, the interpretation of the resistivity patterns, although combined with agronomic information, can be rather intricate.
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