Evaluation of the effect of micro-topography of a potato field on electrical resistivity tomography measurements to assess non-uniform soil moisture patterns in Sandy oil

Abstract

In temperate areas, irrigation in sandy soil is most of the time essential. Literature on the efficiencies of irrigation has highlighted different infiltration patterns. The purpose of this study was therefore to measure infiltration pattern with new non-invasive technique such as ERT after an irrigation event to measure irrigation efficiency. To address this question, we firstly designed the best ERT protocol with the specific microtopography of a potato field using virtual ERT measurements. The best array was the Wenner-alpha + Dipole-dipole. This latter was also resilient to a micro-topography change even though WC underestimation in ridges and WC overestimation in furrows on the first 5cm were observed. After this, we used ERT on the field to follow up and explain the different infiltration patterns caused by the potato canopy and the micro-topography. After an irrigation of 25mm, we observed that water was more likely to infiltrate in furrows (+20% of VWC) rather than in ridges (+2% of VWC). This pattern was explained by the canopy effect. We also determined the root density by counting the number of roots on a framework composed of 5cm by 5cm cell. Roots were mostly present in ridges on the first 50cm with 8 roots/cell causing important RWU bulb. In furrows, less than 2 roots by cell were counted.