Management zone delineation using a modified watershed algorithm

Le zonage intra-parcellaire est une méthode couramment utilisée pour gérer la variabilité intra-parcellaire. Ce concept consiste à partitionner une parcelle en zones de management selon une ou plusieurs caractéristiques du sol et/ou du couvert végétal de cette parcelle. Cet article propose une méthode de zonage originale, basée sur l'utilisation d'une méthode de segmentation d'image puissante et rapide : l'algorithme de ligne de partage des eaux. Cet algorithme d'analyse d'image a été adapté aux spécificités de l'agriculture de précision. Les performances de notre méthodes ont été testées sur des cartes biophysiques haute résolution de plusieurs champs de blé situés en Bourgogne. / Site-specific management (SSM) is a common way to manage within-field variability. This concept divides fields into site-specific management zones (SSMZ) according to one or several soil or crop characteristics. This paper proposes an original methodology for SSMZ delineation which is able to manage different kinds of crop and/or soil images using a powerful segmentation tool: the watershed algorithm. This image analysis algorithm was adapted to the specific constraints of precision agriculture. The algorithm was tested on high-resolution bio-physical images of a set of fields in France.ZONAGE;PARCELLE;TELEDETECTION;BLE;SEGMENTATION D'IMAGE;AGRICULTURE DE PRECISION;FRANCE;BOURGOGNE;PRECISION AGRICULTURE;MANAGEMENT ZONES;REMOTE SENSING;IMAGE ANALYSIS;WATERSHED SEGMENTATION

Yield sensing technologies for perennial and annual horticultural crops: a review

Yield maps provide a detailed account of crop production and potential revenue of a farm. This level of details enables a range of possibilities from improving input management, conducting on-farm experimentation, or generating profitability map, thus creating value for farmers. While this technology is widely available for field crops such as maize, soybean and grain, few yield sensing systems exist for horticultural crops such as berries, field vegetable or orchards. Nevertheless, a wide range of techniques and technologies have been investigated as potential means of sensing crop yield for horticultural crops. This paper reviews yield monitoring approaches that can be divided into proximal, either direct or indirect, and remote measurement principles. It reviews remote sensing as a way to estimate and forecast yield prior to harvest. For each approach, basic principles are explained as well as examples of application in horticultural crops and success rate. The different approaches provide whether a deterministic (direct measurement of weight for instance) or an empirical (capacitance measurements correlated to weight for instance) result, which may impact transferability. The discussion also covers the level of precision required for different tasks and the trend and future perspectives. This review demonstrated the need for more commercial solutions to map yield of horticultural crops. It also showed that several approaches have demonstrated high success rate and that combining technologies may be the best way to provide enough accuracy and robustness for future commercial systems

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

Linking the transpirable soil water content of a vineyard to predawn leaf water potential measurements

International audienceA new expression of the time derivative of predawn leaf water potential was proposed by equalizing two expressions of the grapevine transpiration. This expression was established when transpiration is the only driver of the vineyard water balance. Under Mediterranean climate, this condition is met for long periods of drought i.e. most of the summer time under the hypothesis that there is no water movement (capillary rise) from the deep layers of the soil. The proposed approach showed that changes in predawn leaf water potential (?pd) values are in inverse relation with the Total Transpirable Soil Water (TTSW) which characterizes the maximal water stock of the soil and in direct relation with reference evapotranspiration (ETo) and the basal crop coefficient (kcb) of the vine. The relation between ?pd changes and cumulated ETo is linear with a slope related to the ratio of 'kcb to TTSW'. This ratio can be therefore estimated from field measurements and climatic data. This approach was tested on two year observations performed by Acevedo-Opazo et al. (2010) in vineyards cultivated with cv. Shiraz and Mourvedre, without any irrigation. Analysis of the data obtained in 49 sites per vineyard for several dates in the very dry summers of 2003 (Shiraz) and 2005 (Mourvedre) showed strong and significant adjustments of the model. These results proved the linear relationship between the sum of ETo and ?pd. For each site of the vineyard, the approach demonstrated the possibility to provide site-specific estimates of the ratio of kcb to TTSW. This theoretical and practical development could have applications for water management and soil studies in Mediterranean vineyards

Is a systematic two-dimensional EMI soil survey always felevant for vineyard production management? A test on two pedologically contrasting mediterranean vineyards

1. Global Workshop on High Resolution Digital Soil Sensing and Mapping, Univ Sydney Fac Agr, Food & Nat Resources, Sydney, AUSTRALIA, 2008. Contacts: [email protected], [email protected], [email protected] audienceThanks to recent technological developments, apparent soil electrical conductivity (ECa) can now be mapped over large areas, providing new data for precision agriculture. However, in Mediterranean vineyards, rooting depth can be greater than usual and the volume of soil that needs to be explored is greater. This study examined two vineyard blocks in southern France and looked at the ability of an ECa map, derived from a commercial mobile EMI system, to predict water-related vineyard variability [defined by variation in a normalised difference vegetation index (NDVI) map of the canopy]. To validate the ECa-canopy relationship, electrical resistivity tomography (ERT) profiles and soil observations (42 soil cores sampled to 4 m depth) were made over seven representative transects across the two blocks. In one of the blocks, the ECa map and the NDVI map were correlated, whereas only weak correlations were found for the other block. The examination of ERT data and soil observations in the first block showed a clear relation between soil electrical properties and soil properties known to influence vine water supply (e.g. bedrock depth) and a good discrimination of ERT measures at the measurement depth explored by EM38. In contrast, the second block showed lower ERT measurements and they were not directly related to any soil property that could cause variations in plant water. The contrasting responses between the two blocks demonstrate, as a prerequisite to ECa survey, the importance of prior and local knowledge of soil pattern

Is systematic EMI two dimensional soil survey suitable for vineyard production management? A test on two pedologically-contrasted Mediterranean vineyards

International audienceThanks to recent technological developments, apparent soil electrical conductivity (ECa) can now be mapped over large areas which provides new data for precision agriculture. However, in Mediterranean vineyards rooting depth can be greater than usual crop and the volume of the soil cover that needs to be explored is more important. This study examined the ability of an ECa map from mobile EM38 to predict water related vineyard variability on two fields. To depict ECa -vineyard relations, Electrical Resistivity Tomography (ERT) profiles and soil observations, (42 boreholes 4 meters deep) were made over 7 representative transects of both fields. In one of the fields, ECa map and NDVI map were found correlated whereas only weak correlations were found for the other one. The examination of ERT measures and soil observations in the former field showed a clear relation between soil electrical properties and soil properties known as influencing vine water supply (e.g. bedrock depth) and a good discrimination of ERT measures at the measurement depth explored by EM38. Conversely the later field showed that the ERT measurements are lower and not directly in relation with any of the soil differentiations that may causes variations in plant water. The contrasted performances between the two fields demonstrates the importance of a prior knowledge of soil patterns as a prerequisite to ECa surve