South Africa Wine Technical Yearbook 2025

JULY

Near-real-time characterisation of vines By Carlos Poblete-Echeverría

The importance of canopy structure and vigour assessment

advantage, as they are closely related to vine balance and plant development during the season. This opens up possibilities for implementing management practices that improve grape quality through directed canopy manipulations, irrigation scheduling and pruning, all based on reliable and concrete information. Main results Canopy characterisation For canopy characterisation (expressed as Leaf Area Index – LAI), using RGB, LiDAR and multispectral images (captured with a drone), showed strong correlations with destructive methods, with agreements of approximately 80%. Rough estimations of vigour on a large scale can be done using satellite information. However, quality-focused winegrowers are now managing premium blocks at a more detailed level, accounting for intra-block variability. Under these conditions, the techniques studied in this project could provide the precise and detailed information needed to achieve this goal. Figure 1 shows an example of the method used to process the LiDAR data. Yield estimation Yield estimation is a critical topic in viticulture, as traditional methods are complicated to implement and can generate significant errors, leading to logistical issues in the cellar. The results of this study confirm that RGB and RGB-D are effective methods for estimating bunch weight in both laboratory and field conditions (Figure 2). However, this approach has some practical limitations. In dense canopies, occlusion of bunches can lead to underestimations of the

The ability to accurately and efficiently assess canopy structure and vine vigour is essential for winegrowers aiming to optimise vineyard management. For instance, monitoring intra-block variability in canopy and vigour allows for the implementation of targeted management practices in specific areas. This approach helps reduce variability by applying management inputs where necessary. Alternatively, if winegrowers want to leverage this variability, they can implement strategies such as selective harvesting, separating the fruit into different quality classes, or selective fertilisation. These strategies can reduce costs and resources by applying nutrients only where needed. Traditional methods for assessing canopy structure and vine vigour require considerable manual effort and expertise. While remote sensing technologies like drones and satellite imagery have improved accessibility, they introduce complexities related to data processing, legal compliance and weather conditions. To address these challenges, a research project was undertaken to explore advanced image based techniques for vineyard monitoring to define canopy characteristics and vigour at the plant level. Techniques evaluated In this project, several non-destructive techniques were studied to determine canopy architecture and other key viticulture parameters (such as yield, water stress and pruning weight). The accurate and rapid quantification of these parameters can provide producers with a significant

FIGURE 1. Workflow of the methodology used to determine canopy volume from LiDAR data. This figure appears in one of the articles published as part of the project: https://www.actahort.org/books/1279/1279_34.htm.

63

TECHNICAL YEARBOOK 2025