Fostering sustainable water use in almond (Prunus dulcis Mill.) orchards in a semiarid Mediterranean environment

This work examines the long-term effects of deficit-irrigation (DI) practices in almond crop (Prunus dulcis Mill.) in agronomical and physiological terms. The trial was conducted during four-year monitoring period (2014–2017), in an experimental orchard (SW Spain), subjected to three irrigation regimes; i) a full-irrigation treatment (F_I), which received 100% of crop evapotranspiration (ET_C); ii) a regulated-deficit irrigation (RDI₅₀), which received 50% of ET_C during the kernel-filling period; and iii) a low-frequency deficit irrigation (LFDI), that was subjected to continuous periods of irrigation-restriction defined in terms of threshold values of leaf-water potential (Ψ_leaf) during the kernel-filling period. During the water stress period, there were monitored Ψ_leaf, stomatal conductance (g_s) and canopy temperature (T_C). Significant improvements in terms of water-use efficiency were found, as no differences in terms of yield between F_I and LFDI were found, leading to the conclusion that significant water savings (between 27 and 40%) can be achieved without compromising the yield. Moreover, threshold values of Ψ_leaf and thermal indicators were defined which will allow establishing future irrigation scheduling without compromising almond yield, especially when DI strategies are being applied.