The use of ERT to identity irrigatation patterns and efficiency in potato fields

Potatoes often need irrigation during dry summer weeks, because of their shallow root system, high water needs, and drought sensitivity. Lack of water at crucial moments can result in low tuber yield and loss of tuber quality. Farmers typically adopt a ridge-furrow plant system in which the fate of rain and irrigation water is not well known. As the incoming water is partitioned by plant leaves and by the microtopography itself, the boundary conditions for hydrological modelling (i.e. spatial distribution of incoming water fluxes) for agricultural decision-making are uncertain. There is a need to develop a better understanding of water and nutrient fluxes, especially under irrigated conditions. Non-invasive imaging techniques, such as electrical resistivity tomography (ERT) are increasingly used in the agricultural context to characterize soil moisture dynamics. Nevertheless, non-uniqueness of the inversion, and errors induced by uncertainties related to the measurement process, still weigh on the application of ERT to high-resolution agricultural problems. In this paper, we explore the artefacts we can expect originating from uncertainties during the ERT measurement process using a virtual experiment. We then show the results of a monitoring experiment performed in a potato field in 2018. Although some artefacts are to be expected from microtopography uncertainty in potato ridge-furrow systems, timelapse ERT monitoring remains a valuable tool to reveal infiltration and soil redistribution patterns after irrigation events. As inversion artefacts due to microtopography uncertainty typically occur in places where we also expect to see rapid soil moisture changes, due to root water uptake, an assessment of the changes of microtopography over the course of the experiment is required to reach reliable and quantitative tomograms. Nevertheless, ERT is a very promising tool to better understand spatio-temporal water dynamics in irrigated potato furrow-ridge plant systems, especially when looking at time-lapse differences during infiltration or water uptake processes and in cases of minor to moderate erosion of the ridges.