In recent years, pistachio (Pistacia vera L.) cultivation is undergoing a great expansion in Spain, which is promising for regions where water and winter chilling are not limiting. Many areas of Castilla y León (Spain) provide suitable conditions for pistachio production, but heat requirement could be a limiting factor. The aims of this study were (i) to investigate the status of pistachios in Castilla y León and the relationships between phenology and agroclimatic conditions and (ii) to assess the performance of three pistachio cultivars (‘Kerman’, ‘Lost Hills’, and ‘Golden Hills’) in a plantation within this region. This work describes the phenological and productive behavior of three pistachio varieties in seven orchards over three years. The chilling requirements were exceeded, and heat accumulation was sufficient to complete the cycle in all seasons. Bloom and harvest occurred later in ‘Kerman’ than in ‘Golden Hills’ and ‘Lost Hills’. In general, ‘Kerman’ had higher nut yield than the other two cultivars but also had more non-split and blank nuts, aspects that should be considered for future plantations. Despite the interannual variability in yield, a trend to increase the production with water received was observed, but this also affected the quality and modified the splitting percentage.

Almond cultivation in the Mediterranean area has undergone important changes leading to the current trend of intensification. In this scenario, low-vigor rootstocks have recently been developed, such as the ‘Rootpac^®’ series, but knowledge about the rootstock’s influence on adaptation to high-density planting systems is very scarce. The objective of this work was to assess the morphological and physiological response of four almond cultivars grafted on ‘Rootpac-20’. To this end, one-year-old almond plants (Prunus dulcis (Mill) D. A. Webb.) cv ‘Penta’ (P), ‘Guara’ (G), ‘Vialfas’ (V) and ‘Soleta’ (S) were grown in pots, irrigated at field capacity (from June to September). Plant height and trunk diameter were measured periodically, and the water use efficiency of production was determined at the end of the trial. Evapotranspiration was measured throughout the experiment. The trunk diameter was greater in S and G at the end of the trial. Similarly, the tallest plants were G while the shortest ones were P. In general, G and S had a higher water use efficiency than V and P. ‘Soleta’ grafted on ‘Rootpac-20’ had higher evapotranspiration values (+25%), which is an important issue when selecting plant material, especially in the case of limited water availability for irrigation.

Stomatal traits are determinants of plant water relations and may differ among cultivars within a given species. These features have been rarely studied in tree crops, such as pistachio (Pistacia vera L.), the cultivation of which is expanding in several Mediterranean countries due to its economics revenues. Therefore, this study aims at characterizing several stomata features (length, width, surface, and density) in three pistachio cultivars (Golden Hills, Lost Hills, and Kerman) growing in Central Spain. In addition, the relationships between these traits and gas exchange and stem water potential (Ψ_s) measurements were explored over the 2025 growing season. Kerman trees had more negative Ψ_s values than the other cultivars when atmospheric demand was high, which translated into lower stomatal conductance and net photosynthesis values. This coincided with lower stomatal density and specific leaf area in Kerman. However, stomata were bigger in Kerman than in the other cultivars. When compared over the course of the day, stomatal conductance in the abaxial leaf surface was, approximately, 70% greater than that observed on the adaxial side of the leaves in the three cultivars. These findings provide relevant insights for understanding the regulation of water relations in this species, which may serve for planning new plantations.

Pistachio acreage is increasing noticeably in Spain. However, water management in these plantations still remains a challenge due to the fact that irrigation in new production regions is still not well defined. In this context, the current study aimed to assess the impact of two contrasting irrigation doses on the water relations, yield, and nut quality of pistachio trees (cv. Kerman) in La Seca (central Spain) over five years. Specifically, the high irrigation treatment (H) received 50% more water than the control (C). Soil moisture, stem water potential (Ψ_s), gas exchange parameters, growth, yield, and nut quality traits were monitored. During summer, a slight decline in Ψ_s was observed, with trees from the C treatment exhibiting the most negative values, indicating a slight dehydration. The dry weight of split nuts, with greater marketing value, was higher in H compared to C over the five-year study period. In general, the nutritional composition of the nuts did not differ between treatments. These results provide useful information for the establishment of a suitable irrigation strategy for pistachio cv. Kerman in central Spain and other regions with similar weather conditions.