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

Abstract

Water is the most limiting factor in irrigated agric ulture, 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. T his work examines the crop coefficients (K C ) based on four drainage lysimeters installed in an experimental young almond orchard. Complementary, two deficit-irrigation trea tments were tested: (1) moderate deficit-irrigation (M DI ), which received 100% of the crop evapotranspiration (ET C ) during the irrigation period, except during the ker nel-filling stage and pre-harvest, when irrigation was 50% of ET C ; and (2) severe deficit irrigation (S DI ), in which water was applied according to the values of leaf-water poten tial at midday ( Ψ leaf ), 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 ( Ψ leaf ) and canopy temperature (T C ) dynamics. The K C 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 Ψ leaf and T C showed a temporal evolution according to defined irrigation strategies. Moreover, signifi cant relationship (r2 = 0.63, P<0.05) was obtained between Yleaf and the difference between l eaf and air temperature values (AT). the difference between leaf and air temperature val ues; evidencing the feasibility of using T C for water-stress management. Thus, the findings hi ghlight the importance of local K C to optimize water use and irrigation scheduling in almond orchards. Keywords : Almond, Deficit-irrigation, Drainage lysimeters, Leaf temperature, Water stress.