Impact of altitude and irrigation on sweet cherry tree water status and fruit production in the mountain agroecosystem of the Jerte valley

Abstract

High environmental variability within a valley challenges fruit production in mountain systems and requires site- specific irrigation management. This study evaluates the effects of altitude (480 m vs. 1030 m a.s.l.) and irrigation strategies (regulated deficit irrigation, RDI, vs. conventional farmer-managed irrigation, FRM) on sweet cherry trees (Prunus avium L.) in the Jerte Valley, Spain, focusing on tree water status, vegetative growth, and fruit quality. Results showed that altitude significantly impacted meteorological variables, tree water needs and water status, phenology, and fruit growth. Trees at 1030 m, under cooler, more humid conditions, exhibited a longer fruit development and less negative values of stem and trunk water potential (>-1.3 MPa), resulting in larger fruit (50% of the cherries were larger than 28 mm) compared to those at 480 m (hotter and drier environment), where fruit grew faster and high evaporative demand led to water stress (water potential below -2.0 MPa) and smaller fruit (50% of the cherries had diameters between 24 and 26 mm). RDI maintained better tree water status and enhanced fruit size, particularly at lower altitudes. Soil water content and stomatal conductance varied by altitude and irrigation treatment, with RDI helping to mitigate water deficit stress in both situations. This research highlights the importance of altitude and irrigation strategy in determining the sustainability and resilience of sweet cherry orchards under climate change. Precision irrigation, particularly RDI, offers a viable strategy to optimize water use while improving harvest value in mountain fruit systems.