Interactions between automated cooling irrigation and basal leaf removal in cv. Barbera grapevines

Over a span of two years, a study on Barbera explored the interactive effects of localized cluster nebulization compared to uncooled vines, alongside the presence or absence of late basal leaf removal, using a full factorial design. In this design, basal leaf removal was implemented in both cooled and uncooled vines. The cooling system employed foggers that delivered a water flow of 11.2 L/h, automatically activating when air temperature exceeded 33 °C and relative humidity dropped below 55%. Throughout both seasons, assessments were made on leaf gas exchange, water status, yield components, and grape composition at harvest. In 2025, additional measurements included cluster temperature, soil water potential, and the evaluation of nebulized water dripping onto the soil. While the presence or absence of basal leaf removal had a minor effect on the gas exchange of the immediately upper leaves, leaf function was positively influenced by cooling in both seasons. In 2025, a direct correlation between cooling and non-limiting pre-dawn water potential was established. On average, the presence of basal leaves around the cluster reduced their temperature by 3-4 °C, while nebulization achieved up to 12 °C of cluster cooling. Late basal defoliation had minimal impact on must composition. Conversely, cooling did not affect yield per vine but resulted in higher malic acid at harvest and significantly reduced the concentration and content of total anthocyanins and phenolics compared to uncooled vines. In the absence of cooling, maintaining leaves around the cluster is crucial for controlling sunburn. This study highlights two main and novel findings: (i) the impact on final grape composition can vary depending on how cluster cooling is achieved (e.g., through simple shading or berry wetting), particularly concerning berry pigmentation; (ii) under the chosen activation conditions, under the row soil management and weather and soil characteristics, the irrigation system effectively serves a dual function: providing the expected cooling and enhancing soil moisture with consequent benefits for leaf physiology.