Effects of complementary irrigation on carob tree (Ceratonia siliqua) physiology and productivity in a Mediterranean semi-arid orchard

Agricultural productivity is threatened by prolonged droughts and intensified desertification caused by climate change highlighting the need for adaptive cropping systems. The carob tree (Ceratonia siliqua L.) is well-adapted to Mediterranean climates and due to its unique characteristics, is a valuable crop both economically and environmentally. In this study, irrigation was applied in a carob tree orchard under two treatments: complementary irrigation (CI) and deficit complementary irrigation (DCI). Climatic parameters such as rainfall, reference evapotranspiration (ET0) and vapour pressure deficit (VPD) were recorded during the two-year experiment (2023–2024). To better understand water stress, stomatal conductance, stem water potential and canopy temperature were measured. In addition, data were retrieved from sensors and dendrometers. Yield and productivity parameters, including fruit quality, were also evaluated. Results showed, that the DCI treatment showed increased production in the second year, while CI improved fruit quality. A negative correlation was found between stem water potential and both air temperature and vapor pressure deficit (VPD). Physiological measurements proved to be a precise method for monitoring the tree´s response to environmental conditions and provide valuable information for irrigation scheduling, while continuous measurements obtained using dendrometers provided good results in monitoring the water status. These findings reveal the dynamics between the environmental conditions and the physiological measurements, paving the way for new studies in understanding and planning carob irrigation aiming to prevent water stress without loss of yield.