terclim by ICS banner
IVES 9 IVES Conference Series 9 High-resolution aerial thermography for water stress estimation in grapevines

High-resolution aerial thermography for water stress estimation in grapevines

Abstract

Aerial thermography has emerged as a promising tool for water stress detection in grapevines, but there are still challenges associated with this technology, particularly concerning the methodology employed to extract reliable canopy temperature values. This consideration is relevant especially in vertically trained vineyards, due to the presence of multiple surfaces which are captured by drone thermal cameras with high-resolution. To test the technology and the data analysis required, a field study was conducted during the 2022-2023 season in a model vineyard with multiple scions-rootstock combinations trained on a vertical shoot-positioning (VSP) system. Additionally, three irrigation regimes were implemented to introduce variability in water stress levels. A commercial Unmanned aerial vehicle (UAV) equipped with an integrated RGB, and thermal camera was used to capture high-resolution aerial images over the vineyard. Eight different pixel extraction methods, considering classical and novel approaches, were tested against manual pixel extraction to determine which method performed the best. From the methods tested, the two Gaussian mixture models (GMM2) showed the best performance in terms of accuracy and precision. The average canopy temperature obtained by this method was contrasted with stem water potential measurements, showing significant differences between well-watered and dryland treatments. Aerial thermography complemented by the GMM2 method shows great potential as a tool for water stress estimation in grapevines, however, several factors play a role in method performance. These include the degree of stress in the vineyard, amount of cover crops, and canopy density amongst others. Suggestions regarding the critical aspects that need to be evaluated further to optimize the methodology and reduce the uncertainties associated to the application of this technology will be discussed in context of the results obtained.

DOI:

Publication date: June 14, 2024

Issue: Open GPB 2024

Type: Article

Authors

Carlos Poblete-Echeverria1*, Thomas Chalmers1, Melane A. Vivier1

1 South African Grape and Wine Research Institute (SAGWRI), Faculty of AgriSciences, Stellenbosch University, Matieland 7602, South Africa

Contact the author*

Keywords

Precision viticulture, Water management, Digital analysis, Pixel extraction methods, Thermal imagery

Tags

IVES Conference Series | Open GPB | Open GPB 2024

Citation

Related articles…

Climate, Viticulture, and Wine … my how things have changed!

The planet is warmer than at any time in our recorded past and increasing greenhouse emissions and persistence in the climate system means that continued warming is highly likely. Climate change has already altered the basic framework of growing grapes for wine production worldwide and will likely continue to do so for years to come. The wine sector can continue to play an important role in leading the agricultural sector in addressing climate change. From developing on…

Influence of cork density upon cork stopper resiliency after opening a sparkling wine bottle

After Champagne popping, the first consumer’s observation is the shape of the cork stopper. Consumers expect a “mushroom shape”. Nevertheless, we sometimes observe a “barrel” shape due to inappropriate cork’s elastic properties. The aim of this study was to follow the loss of cork stopper resiliency during 26 months according to the density (d) of the cork in contact with the wine. 1680 disks were weighed + measured and divided in 6 density classes: High (H1 d= 0,19 g/cm3 – H2 d= 0,21 g/cm3), Medium (M, not studied) and Low (L1 d= 0,13 g/cm3 – L2 d= 0,14 g/cm3). Then, 138 technical cork stoppers were produced for each of the 4 studied groups. These corks consisted of an agglomerated natural cork granule body to which two natural cork disks were glued. A total of 552 bottles of sparkling wine were closed with these corks and open after 13, 19 and 26 months to follow cork resiliencies. Wine bottles were stored horizontally; thus, the external natural cork disks were in contact to the wine. During the 26 months of the study, highly significant differences (ANOVA) were observed between the resiliencies of H-corks and those of L-corks, whatever the time studied. The diameters of the L-corks were statistically higher than those of the H-corks. No significant differences were observed between L1 and L2 corks. At the opposite, differences were noted between H1 and H2 at 19 and 26 months. This could be explained by the heterogeneity of the resiliency that was higher for H-corks than for L-corks. Finally, the corks were visually (12 judges) divided in 3 classes corresponding to high (expected mushroom shape, i.e high resiliency), medium (irregular shape of the disk in contact with the wine and/or low premature deterioration of the expected resiliency) and low qualities (barrel shape = premature deterioration of the resiliency). The corks were also divided in 3 categories corresponding to 0-33%, 34-66% and 67-100% resiliency. A strong correlation was noted between the visual and the instrumental categorizations. This study strongly evidenced 1) the importance of the cork density on the cork stopper behaviour when opening the bottle and 2) the interest of an instrumental approach reflecting the consumer’s perception.

Effect of terroir on the quality evolution of Cabernet-Sauvignon in Penedès A.0.C.

Le Cabernet-Sauvignon est un cépage très répandu dans la région du Penedès (Espagne) où cette variété peut bien s’adapter et donne des produits de haute qualité.

Temperature variability inside a wine production area and its effect on vine phenology and grape ripening. An example from the Saint-Emilion-Pomerol

AIM: the aim of this study was to develop a method for fine-scale temperature zoning. The effect of temperature variability on vine phenology and grape composition was assessed in the production area of Saint-Emilion

Study of the sensory dimension of the wine typicality related to a terroir and crossing with their viticultural and oenological characteristics

The typicality of a product can be characterized by properties of similarity in relation to a type, but also by the properties of distinction.