Estimating Almond Crop Coefficients and Physiological Response to Water Stress in Semiarid Environments (SW Spain)

Water is the most limiting factor in irrigated agriculture, mainly in Mediterranean environments, as in the case of southwest Spain. In this area, almond is one of the most valuable crops due to its high drought tolerance. This work examines the crop coefficients (KC) based on four drainage lysimeters installed in an experimental young almond orchard. Complementary, two deficit-irrigation treatments were tested: (1) moderate deficit-irrigation (MDI), which received 100% of the crop evapotranspiration (ETC) during the irrigation period, except during the kernel-filling stage and pre-harvest, when irrigation was 50% of ETC; and (2) severe deficit irrigation (SDI), in which water was applied according to the values of leaf-water potential at midday (Ψleaf), this being maintained at between -1.6 and -2.0 MPa. The crop’s physiological response to water stress was monitored throughout the study period by assessing the leaf-water potential (Ψleaf) and canopy temperature (TC) dynamics. The KC values changed from 0.4 at the beginning of irrigation period to a maximum of 1.1 during the maximum evaporative demand period. From this stage on, the Kc gradually decreased to 0.4 at the end of the season. In physiological terms, both Ψleaf and TC showed a temporal evolution according to defined irrigation strategies. Moreover, significant relationship (r2 = 0.63, P<0.05) was obtained between Yleaf and the difference between leaf and air temperature values (AT). the difference between leaf and air temperature values; evidencing the feasibility of using TC for water-stress management. Thus, the findings highlight the importance of local KC to optimize water use and irrigation scheduling in almond orchards.