A sundial vineyard: impact of row density and orientation on cv. Cabernet-Sauvignon physiology and grape composition, insights to face a climate change scenario

Abstract

An experimental vineyard with a radial array was planted in 2018, to provide valuable information on the relationship between orientation and planting density on plant physiology and cluster microclimate, and the consequent impacts on grape secondary metabolites, including aromas and polyphenols. This project will allow us to find the best combination between these factors in order to improve water use, and grape quality in our current climate scenario in the Maipo Valley, and give us insights into facing the challenges of climate change.

The vineyard has a radial layout with rows of 15 plants every 6°, starting with a row distance of 50cm and ending with 200cm, planted with Cabernet-Sauvignon cv. (https://www.youtube.com/watch?v=QWFFAvTjy6c&t=79s ). During the 2023-2024 season, evaluations of water potential, stomatal conductance, and cluster microclimate were made, measuring light in the cluster’s zone with a 1-meter photosynthetically active radiation (PPF) bar and cluster temperature with an infrared radiometer (IRT) three hours before and after the zenith. Also, leaf chlorophyll concentration was assessed on both sides of each row.

Also, PPF and IRT were measured continuously in the central plant (8th) of the rows between 180° and 342°. Simultaneously, a weather station was placed in the center of the vineyard so daily curves of environmental conditions and within the cluster zone were recorded including PPF outside the canopy.

All bunches were analyzed, for which whole plants were harvested and the incidence and severity of berry dehydration were evaluated. Additionally, analyses of acids, aromas and polyphenols were carried out in the grapes.

Differences were observed in the amount of PPF intercepted in the cluster area, (angle p < 0.01; density p < 0.05), cluster temperature (angle p < 0.01; density ns), and chlorophyll concentration (angle p < 0.01; density p < 0.01). Stomatal conductance showed significant differences due to density (p-value < 0.01), being higher in the densest zone. In contrast, no differences were found in the xylem water potential at solar noon, with values between -0.76MPa and -0.88 MPa. Relevant to say is that the radiation expected due to latitude modeling did not match our results, mainly because the canopy growth and vigor depended on the orientation, increasing the importance of actual measurements of cluster microclimate.