Response to moderate water stress imposed after pit hardening in mature table olive orchard cv. Azapa

Abstract

Table olive trees which grow under high evaporative demand with no rainfall in arid zones such as the Azapa Valley, Arica and Parinacota Region, Chile, depend exclusively on irrigation; a common practice recommended in areas with low water availability is regulated deficit irrigation (RDI). The aim of the study was to describe the response of olive to variable water supply after pit hardening to harvest (167–199days) in a mature orchard of cv. Azapa in a biennial cycle. Full replenishment was scheduled until the end of pit hardening (11 weeks after full bloom), then four treatments were compared: T0, 100% of crop evapotranspiration (ETc); T1, 80% ETc; T2, 60% ETc and T3, 40% ETc. The water stress imposed was considered as moderate, according to stomatal conductance data. Water relations were affected more by the level of water supply than by crop load, with a significant reduction of midday water potential in the most restrictive treatment. Vegetative growth occurred mainly during the unstressed period, while shoot growth rate was affected by crop load level. Fruit size distribution in the “on” year (12100kgha−1) were 14 and 20% higher in control and T1 (−2.0MPa), while a reduction in fruit volume was found with −2.7MPa (T3). In the “off” year, yield in RDI treatments were 49 and 67% lower than control, without differences in fruit size distributions. This response could be related to the increase in the rigidity of the cell wall and osmotic adjustment in the most restrictive treatment, as an adaptive response of the trees to arid conditions.