In commercial date palm cultivation, a common pre-harvest practice involves withholding irrigation for approximately two months to reduce fruit water content, enabling packing without the need for external drying (e.g., oven treatment) and thereby enhancing profitability. However, the physiological response of the trees to reduced water availability and salt accumulation in the root zone under the resulting drought regime remains poorly understood. This study monitored root zone dynamics during the drying period by employing time-lapse Electrical Resistivity Tomography (ERT) to compare two irrigation strategies: a conventional method based on meteorological data (and a pre-determined crop coefficient), and an Irrigation on Demand (IOD) approach, which irrigates based on real-time soil matrix potential and pre-defined set points.
The field site is located at an experimental plantation near Kibbutz Gilgal (Jordan Valley). ERT surveys were conducted during August 2024. Petrophysical relations were calibrated to link the electrical signal to water content and salt concentrations. Complementary measurements included soil oxygen and moisture sensors at multiple depths, and sapflow sensors in tree stems to assess transpiration. A physics-informed machine-learning framework was applied for data integration and analysis.
Results indicate that the IOD method reduced irrigation volume by approximately 25%, while maintaining higher transpiration rates and root-zone oxygen levels throughout the drying period. ERT imaging revealed distinct differences in soil moisture and salinity patterns between the two treatments, with salinity concentrations exceeding double those observed in the conventional method under the IOD regime.
