The irrigation surface of olive orchards has increased over recent decades. In zones affected, deficit irrigation scheduling is a must. The aim of this work was to study water stress management based on reference equations for midday stem water potential. An experiment was conducted over three seasons in Seville (Spain) from 2020 to 2022. A young hedgerow olive orchard (cv Manzanilla de Sevilla) was irrigated using three different treatments: Control (full irrigated), RDI, and Rainfed, in a completely randomized design (six replications). The midday stem water potential and leaf conductance were measured throughout the three seasons. Stem water potential was more sensitive to water stress than leaf conductance and showed a clearer impact and rehydration. Individual data of stem water potential were grouped according to leaf conductance reduction. The relationship of these stem water potentials and temperature or vapor pressure deficit was significant, linear, and aligned to published baselines. Scattering in these equations increased when the leaf conductance reduction was greater. These reference equations would be useful to define moderate water stress conditions in the most sensitive processes, such as vegetative or fruit growth. Definition of severe water stress conditions would be better established with constant values.

Endocarp development in olive trees includes three periods: growth (Period I), massive sclerification (Period II) and maximum hardening (Period III). The two first are strongly related to yield and irrigation management. Period I was reported to coincide with mesocarp cell division and thus with final fruit size. Period II was considered to be the most drought-resistant phenological stage. However, little is known in olive trees about the length of these periods and their capacity for predicting fruit size at harvest. The aim of this work was to evaluate the length of both periods in different cultivars and different location of full irrigated orchards. We also aimed to study the fruit feature impact on harvest at the end of Period I. Data from full irrigated olive orchards of cv Cornicabra, Arbequina and Manzanilla in two different locations (Ciudad Real, Central Spain, and Seville, South Spain) were used. The pattern of pit-breaking pressure throughout the season was measured with fruit samples for several years (2006 to 2022). These data and climatic data were used to compare different estimation methods for the length of Period I and II of endocarp development. Then, fruit volume and dry weight at the end of Period I were used to estimate fruit features at harvest. Results suggest that the Period I length was less temperature- and cultivar-dependent than expected. The duration of this period was almost constant at around 49 days after full bloom. Thermal time was negatively correlated with fruit size at the end of Period I. On the contrary, a lineal thermal model presented the lowest variability when estimating the Period II length, which was also affected by the cultivar. The best fit between fruit dry weight and volume at Period I vs. harvest was unique for oil cultivars (Cornicabra and Arbequina), while cv Manzanilla presented a different relationship. A temperature increase in the future would not affect the Period I length but would reduce the fruit size at the end of this period and at harvest.

Recurso audiovisual práctico centrado en la medición del potencial hídrico en cultivos leñosos (olivo, almendro y pistacho). Se muestra el uso de la cámara de Scholander y las adaptaciones de hojas según la especie. Incluye ejemplos de interpretación en función del desarrollo del cultivo. Facilita la aplicación de estrategias de riego deficitario controlado. Este recurso didáctico está dirigido a estudiantes del Grado en Ingeniería Agrícola y del Máster en Ingeniería Agronómica, en asignaturas como Cultivos leñosos, Fruticultura o Gestión de los Recursos Hídricos. Se utiliza como material de apoyo en prácticas y docencia aplicada, permitiendo al alumnado comprender la medición del potencial hídrico en especies leñosas y su interpretación en las distintas fases del cultivo. Favorece el desarrollo de competencias en manejo eficiente del agua y diseño de estrategias de riego deficitario controlado. El potencial hídrico es un indicador fisiológico clave que permite evaluar el estado hídrico de la planta. Su medición, habitualmente mediante cámara de presión de Scholander, proporciona información directa sobre el nivel de estrés hídrico del cultivo. En cultivos leñosos es una herramienta fundamental para la gestión del riego, ya que permite establecer umbrales de respuesta según la fase de desarrollo del cultivo. Este enfoque es clave en estrategias de riego deficitario controlado, donde se busca optimizar el uso del agua sin comprometer la productividad ni la calidad del cultivo.