Monitoring plant water status is relevant for the sustainable management of irrigation under water deficit conditions. Two treatments were applied to an early-maturing nectarine orchard: control (well irrigated) and precise deficit irrigation (PDI, based on soil water content thresholds). Moderate water deficits generated by PDI were assessed by comparing terrestrial: stem water potential (Ψ_stem) and gas exchange parameters, with remote: canopy temperature, normalized difference vegetation (NDVI), and soil adjusted vegetation index (SAVI), plant water status indicators. The Ψ_stem was the only indicator that showed significant differences between treatments. NDVI and SAVI at the postharvest period were appropriate indexes for estimating winter pruning, although they did not serve well as plant stress indicator. Vapor pressure deficit along with Ψ_stem values were able to predict remote sensing data. Ψ_stem and canopy to air temperature difference values registered the highest signal intensity and NDVI the highest sensitivity for detecting water deficit situations. The results suggest that care should be taken when using instantaneous remote indicators to evaluate moderate water deficits in deciduous fruit trees; more severe/longer water stress conditions are probably needed. The proposed PDI strategy promoted water saving while maintaining yield, and could be considered a promising tool for semi-arid agrosystems.

The use of hydrogeophysical methods provides insights for supporting optimal irrigation design and management. In the present study, the electrical resistivity imaging (ERI) was applied for monitoring the soil water motion patterns resulting from the adoption of water deficit scenarios in a micro-irrigated orange orchard (Eastern Sicily, Italy). The relationship of ERI with independent ancillary data of soil water content (SWC), plant transpiration (T) and in situ measurements of hydraulic conductivity at saturation (K_s, i.e., using the falling head method, FH) was evaluated. The soil water motion patterns and the maximum wet depths in the soil profile identified by ERI were quite dependent on SWC (R² = 0.79 and 0.82, respectively). Moreover, ERI was able to detect T in the severe deficit irrigation treatment (electrical resistivity increases of about 20%), whereas this phenomenon was masked at higher SWC conditions. K_s rates derived from ERI and FH approaches revealed different patterns and magnitudes among the irrigation treatments, as consequence of their different measurement scales and the methodological specificity. Finally, ERI has been proved suitable for identifying the soil wetting/drying patterns and the geometrical characteristics of wet bulbs, which represent some of the most influential variables for the optimal design and management of micro-irrigation systems.