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

Cell-penetrating nanobiosensors for pointillistic intracellular Ca 2+-transient detection

Small-molecule chemical calcium (Ca2+) indicators are invaluable tools for studying intracellular signaling pathways but have severe shortcomings for detecting local Ca2+ entry. Nanobiosensors incorporating functionalized quantum dots (QDs) have emerged as promising alternatives but their intracellular use remains a major challenge. We designed cell-penetrating FRET-based Ca2+ nanobiosensors for the detection of local Ca2+ concentration transients, using commercially available CANdot565QD as a donor and CaRuby, a custom red-emitting Ca2+ indicator, as an acceptor. With Ca2+-binding affinities covering the range of 3-20 μM, our CaRubies allow building sensors with a scalable affinity for detecting intracellular Ca2+ transients at various concentrations. To facilitate their cytoplasmic delivery, QDs were further functionalized with a small cell-penetrating peptide (CPP) derived from hadrucalcin (HadUF1-11: H11), a ryanodine receptor-directed scorpion toxin identified within the venom of Hadrurus gertschi. Efficient internalization of QDs doubly functionalized with PEG5-CaRuby and H11 (in a molar ratio of 1:10:10, respectively) is demonstrated. In BHK cells expressing a N-methyl-d-aspartate receptor (NMDAR) construct, these nanobiosensors report rapid intracellular near-membrane Ca2+ transients following agonist application when imaged by TIRF microscopy. Our work presents the elaboration of cell-penetrating FRET-based nanobiosensors and validates their function for detection of intracellular Ca2+ transients. © 2014 American Chemical Society

An iterative region growing algorithm to generate fuzzy management zones within fields

International audienceManagement zones are within-field spatial units that are more homogeneous than the rest of the field and that have different factors or values than other areas of the field. While most algorithms tend to delineate fixed management zone borders, it is acknowledged that within-field variations between management zones are more gradual than sharp, mainly because of smooth variations in soil and landscape characteristics. In this work, an approach is proposed to account for the transient observations between management zones by delineating within-field fuzzy management zones. Observations within transition zones could belong to more than one zone, and this perhaps should be accounted for during the delineation process. Theoretical fertilization-based case studies, i.e. high and weak environmental constraints, were considered to show the interest of membership frequencies to refine yield-based management zones when user's expertise and management decisions come into play

Découverte : étude de la qualité de l'eau au lac Split

Lié a un projet du CRDI sans en être un produit directHôte: Charles Tisseyr

Production gap analysis: an operational approach to yield gap analysis using historical high-resolution yield data sets

International audienceYield potential has major interests in agronomic modelling such as for the computation of fertilizer recommendations. Most precise estimates of this potential can be generated with crop modelling approaches. However, such potential is often theoretical because it has never been obtained in the field and requires lots of input data to be computed, e.g. soil characteristics, management practices. In this study, a decomposition of this theoretical yield potential into a series of intermediate and more realistic potentials, denoted here production potentials, is proposed. This work comes along with a simple method relying on historical high-resolution yield datasets to compute site-specific production potentials and production gaps, i.e. the differences between actual yield and production potentials. Application of the methodology to a real database of yield mapping has proved of interest to identify areas with similar production potentials but different production gaps. Advantages and concerns regarding the use of such production potentials are discussed at the end of the study

Grape inspection by machine vision

There is no mean except machine vision to objectively inspect grape visual features like general shape fruit (trapezoidal, cylindrical) and compactness. Other measurements like berry size and homogenity of berry size inside the grape may be conducted more rapidly with machine vision than classical sampling and sizing methods. An image processing which allows to extract some grape features (shape features, compactness features and berry size features) was developped. It was tested on four different grape varieties. Results are presented at the end of the document and show it is rather easy to investigate shape and berry size features. Investigation of grape compactness may involve several criteria and a complex aggregation of these criteria in order to take a decision. / La vision est le seul moyen pour une inspection visuelle objective des caractéristiques des grappes comme la forme générale (trapézoïdale, cylindrique) et la compacité. D'autres mesures comme la taille des grappes et l'homogénéité de la taille des grains dans la grappe peuvent être visualisées plus rapidement q'avec les méthodes d'échantillonnage classiques. Une analyse d'image permettant d'extraire des caractéristiques telles que la forme, la compacité et la taille des grains a été développée. Le système a été testé sur quatre variétés. Les résultats sont présentés et montrent que la forme de la taille des grains est facile à appréhender. La compacité des grappes induit plusieurs critères et une agrégation complexe de ces critères doit être réalisée pour prendre une décision

A new approach for zoning irregularly-spaced, within-field data

International audienceManagement zones can be defined as homogeneous regions for which specific management decisions are to be considered. The delineation of these management units is important because it enables or at least facilitate growers and practitioners performing site specific management. The delineation of management zones has essentially been performed by (i) clustering techniques or (ii) segmentation algorithms arising from the image processing domain. However, the first approach does not take into account the spatial relationships in the data, and is prone to generate a large number of fragmented zones while he second methodology has only been dedicated to regularly-spaced, within-field data. This work proposes a new approach to generate contiguous management zones from irregularly-spaced within-field observations, e.g. within-field yield, soil conductivity, soil samples, which are a very important source of data in precision agriculture studies. A seeded region growing and merging algorithm has been specifically designed for these irregularly-spaced observations. More specifically, a Voronoi tessellation was implemented to define spatial relationships between neighbouring observations. Seeds were automatically placed at specific locations across the fields and management zones were first expanded from these seeds. The merging procedure aimed at generating more manageable and interpretable zones. The merging algorithm was defined in a way that made it possible to incorporate machinery and technical management constraints. Experiments demonstrated that the proposed methodology was able to generate relatively compact and contiguous management zones. Furthermore, machinery and technical constraints were shown to significantly influence the results of the delineation which proved the importance of accounting for these considerations

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

Etude de la qualité de distribution des pesticides à partir de technologies DGPS et de cartographies de la distribution

Vines were located by using DGPS technology and sprayed with a solution mixed with water and Rhodamine-B instead of pesticide by air-diffusion sprayer. The Vine Leaf Samples in height and depth direction and Cotton Fabrics Samples in vine height direction and ground width direction were taken to measure the quantity of spray deposits and calculate the area of Vine Leaf. Also, the distribution curves and map were derived. Results indicated that the distribution of spray deposits varied very much in vines: most of the spray deposits distributed at the height of 500-700mm, and decreased in turn if higher or lower; as for luxuriant vines, the quantity of deposits decreased along the depth direction, but for the vines with sparse leaves, the middle part along the depth direction contained the most spray deposits; the quantity of spray deposits on the ground was very little. The results had great positive significance in choosing and adjusting vine spray instruments, and in the guidance of pesticide accurate spray in precision viticultur