Unveiling water dynamics at soil-plant level using geophysical imaging under sustainable farming practices in Mediterranean citrus groves

This study assesses the combined effects of different water regimes (full irrigation−FI versus regulated deficit irrigation−RDI) and soil management practices (with/without the use of organic soil mulching−OM) on spatiotemporal patterns of soil water content (SWC) (case study 1) and soil-plant-water dynamics (case study 2) in a citrus orchard located in Mediterranean semi-arid climate. Repeated electrical resistivity tomography (ERT) surveys were performed adopting dipole-dipole electrode arrays within two periods of the irrigation seasons 2022-2023 (both at case study 1 and 2), before and during irrigation events. Electromagnetic induction (EMI) technique was applied at case study 2 under dry conditions (no irrigation) in order to complement by spatial continuous geophysical coverage. Electrical resistivity (ER)-dependent parameters (e.g., SWC; soil temperature, Tsoil) and continuous tree water status measurements, i.e., crop transpiration (TSF) and trunk water potential (TWP), were also acquired. At case study 1, the OM reduced the ER and increased SWC by 14 % under RDI (p-value = 0.00), suggesting lower soil evaporation and enhanced moisture retention. Both ERT and EMI showed lower ER and higher apparent conductivity under mulched soils compared to bare soils at case study 2. As consequence of irrigation, ER was increased by OM up to 14 %, resulting in an inverted trend of SWC and Tsoil in contrast to the observed TSF and TWP. In conclusion, the use of geophysical imaging and complementary measurements offered practical insights by contributing to improve our understanding on key soil-hydrology related processes and soil-plant water dynamics in citrus groves under OM application.