Towards an empirical model to estimate the spatial variability of grapevine phenology at the within field scale

The aim of this study is to propose an empirical spatial model to estimate the spatial variability of grapevine phenology at the within-field scale. This spatial model allows the characterization of the spatial variability of a given variable of the fields through a single measurement performed in the field (reference site) and a combination of site-specific coefficients calculated through historical information. This approach was compared to classical approaches requiring extensive sampling and phenology models based on climatic data, which do not consider the spatial variability of the field. The study was conducted on two fields of Vitis vinifera, one of cv Cabernet Sauvignon (CS, 1.56 ha) and the other one of cv Chardonnay (CH, 1.66 ha) located in Maule Valley, Chile. Date of occurrence of grapevine phenology (budburst, flowering and veraison) were observed at the within field level following a regular sampling grid during 4 seasons for cv CS and 2 seasons for cv CH. The best results were obtained with the devised spatial model in almost all cases, with a Root Mean Square Errors (RMSE) lower than 3 days. However, if the variability of phenology is low, the traditional method of sampling could lead to better results. This study is the first step towards a modeling of the spatial variability of grapevine phenology at the within-field scale. To be fully operational in commercial vineyards, the calibration process needs simplification, for example, using low cost, inexpensive ancillary information to zone vineyards according to grapevine phenology

Automatisation de la prétaille en long bois

A method of image analysis that allows one to design an automatic detection system of the long log that needs to be preserved, description of the image processing steps, of the criteria used for the decision, results of two image and decision softwares, conclusion and research axis are the topics covered in this article. / Communication qui présente une méthode d' analyse de l' image permettant la mise au point d'un système de détection automatique du long bois à préserver , description des étapes du traitement de l'image , des critères utilisés pour la décision , résultats des deux logiciels image et décision, conclusion et axe de recherche

Fuzzy reasoning for long cane pruning : a relaxation algorithm for complex vine configurations

Long cane pruning cannot be performed at present with machines which do not allow the selection and the saving of the desired wood. Research is being conducted to design a system enabling such an automatic selection. The system consists of an image processor which individualises and tracks the different woods in the image. A decision device simulates the pruner's reasoning by choosing the most appropriate long wood to save according to wood features measured on the images. This decision device is based on a fuzzy multi-criteria decision-making (FMCDM), the preference defined by th expert on the criteria values are represented by fuzzy sets. Results show that the decision system fitted with the pruner's decisions in the vineyard. The decision system which was developed is able to work an standard vine pruning cases. Sometimes, however, the vine configuration is not good (problems of frost, hail storm or mechanised operations can damage woods). In such cases, the proposed decision system is not able to choose the most appropriate long wood because it is not accurate enough to make a distinction among very bad woods. Nevertheless, the pruner always takes a decision. In such cases, the pruner's reasoning is not the same, the pruner becomes more laxist and makes a relaxation of his preferences. This paper presents the relaxation algorithm which was used to simulate the pruner's reasoning when the system faces non standard pruning cases. / Le travail a pour but de développer un système pour choisir automatiquement le long bois à préserver. Le système comprend un processeur d'images qui individualise les sarments. Le système de décision simule le raisonnement du tailleur en fonction des paramètres mesurés sur l'image : il est basé sur un système de logique floue multi-critères. Le système de décision fonctionne pour les cas de vigne standard. Dans le cas de vignes complexes, tous les sarments sont trop mauvais. Dans ce cas le raisonnement n'est plus le même. Le papier présente l'algorithme de relaxation utilisé pour simuler le raisonnement du tailleur dans ces cas

Viticulture de précision et état hydrique. II : Comportement quantitatif et qualitatif de zones intra-parcellaires définies à partir de la cartographie des potentiels hydriques

International audienceThe within field variability of grape quantitative and qualitative parameters has recently become an important issue in viticulture due to the impact that such variability has on the wine quality. Spatial, high-resolution systematic measurements of these parameters is becoming a reality in modern viticulture. A within field zoning of a Syrah vineyard located at INRA Pech Rouge (Gruissan, France) was carried out. The zoning was based on the mapping of the predawn water potential changes, measured from flowering to ripening. The aforementioned methodology, performed during 2003-04 seasons, allowed us the division of the field into four zones which were compared with an irrigated zone used as a control. Different quantitative (berry weight, yield, SFE, pruning weight, trunk diameter) and qualitative (sugars, total acids, pH, anthocyanins, IPT) parameters were measured in each zone. Each of the five zones (the 4 zones delimited and the irrigated control) was harvested individually. The results of the two different seasons show that, as long as the water restriction rises, the enrichment of the components linked with quality is reinforced. Simultaneously, vigour and yield are reduced. Yield reduction is mostly due to the reduction in berry size. Nevertheless, there is a threshold of water restriction, beyond which there are no further gains in qualitative components content, whereas yield and quantitative parameters keep on decreasing. For the most severe water deficit, all parameters (quantitative and qualitative) decrease, causing an important weakness in the vine. Such conditions, if sustained throughout time, may be negative for wine perennity. This situation requires further research aiming at determining the optimum water restriction thresholds for each variety/trellis system/"terroir" situation, and therefore, achieving the best quality/yield relation. These works finally aim at providing references to local growers to perform qualitative irrigation management. It is also necessary to study the physiological aspects that explain the adaptive mechanisms of different varieties to the water characteristics of Southern France's Mediterranean "terroirs" in relation with global warming. Finally, this research work points out the interest that site-specific management of the vineyard may present regarding quality improvement (including differential, variable irrigation for each zone and selective harvest)La variabilité intra-parcellaire des paramètres quantitatifs et qualitatifs du raisin est une problématique actuelle d’importance considérable car elle a des conséquences qualitatives sur le vin. La mesure systématique, dans l’espace, et avec des résolutions élevées, de ces paramètres commence à devenir une réalité en viticulture. Un zonage intra-parcellaire a été effectué sur une parcelle de Syrah située sur l’Unité Expérimentale INRA de Pech Rouge (Gruissan, France). Ce zonage s’appuie sur une cartographie et une classification ascendante hiérarchisée de l’évolution du potentiel foliaire de base des souches de la nouaison à la maturité. Cette méthodologie, mise en œuvre pendant les années 2003 et 2004, a permis de différencier quatre zones qui ont été comparées avec un témoin irrigué. Pour chaque zone, différents paramètres "quantitatifs" (poids des baies, rendement, surface foliaire exposée potentielle, poids de bois de taille, circonférence de tronc) et "qualitatifs" (teneur en sucre, acidité totale, PH, anthocyanes et IPT) ont été mesurés. Chacune des 5 zones (4 zones identifiées et témoin irrigué) a été récoltée et vinifiée de manière individuelle. Pour les deux millésimes étudiés, les résultats mettent en évidence que lorsque les niveaux de contrainte hydrique augmentent, la richesse en composants liés à la qualité (phénols, sucres,…) est renforcée malgré une légère réduction de vigueur et de rendement induit notamment par diminution de la taille de la bai

Viticulture de précision et état hydrique. I: Cartographie du potentiel hydrique et intérêt pour le zonage à un niveau intra-parcellaire

International audienceAn experiment was carried out over two years (2003-2004) in order to monitor the spatio-temporal variability of the predawn water potential at a within field scale. The predawn water potential was measured on 49 points within a field of 1.2 ha. Respectively 7 and 6 measurements were performed at different times in 2003 and 2004. The main results of this work showed that the within field variability of the predawn water potential was significant. It also highlighted the temporal stability of the variability. The zoning performed according to the predawn water potential values was linked to other parameters such as leaf area, trunk circumference, soil resistivity, etc. The result confirmed the temporal stability of the within field variability. It also showed the opportunity to use high resolution data (remote sensing, monitoring systems mounted on conventional machinery) as decision support system to assess a similar zoning or to perform target sampling for a better assessment of the field water statusUne expérimentation a été conduite pendant deux ans (2003-2004) afin de suivre la variabilité spatio-temporelle du potentiel hydrique de base à une échelle intra-parcellaire. Le potentiel de base a été mesuré sur 49 points à l’intérieur d’une parcelle de 1,2 ha. Ces mesures ont été répétées à 7 et 6 dates différentes respectivement en 2003 et 2004. Les principaux résultats de cette expérimentation montrent que la variabilité intra-parcellaire du potentiel de base est importante. Ils mettent également en évidence la stabilité temporelle de la variabilité observée. Le zonage effectué sur la base du potentiel hydrique était lié à d’autres paramètres tels que la SFEp, la circonférence des ceps, la résistivité du sol, etc. Ce lien confirme la stabilité temporelle de la variabilité observée. Il permet également d’envisager d’utiliser des données à hautes résolution (télédétection, capteurs embarqués sur machines) pour effectuer un zonage similaire ou pour servir d’outils d’aide à l’échantillonnage orienté pour une meilleure estimation de l’état hydrique de la parcell