References of "Tychon, Bernard"
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See detailSensitivity of simulated surface wetness duration to meteorological variations in three different regions of Grand-Duchy of Luxembourg
Mahtour, Abdeslam ULg; El Jarroudi, Moussa ULg; Hoffmann, Lucien et al

Poster (2010, November 23)

Surface wetness duration (SWD) is an important factor influencing the occurrence of winter wheat diseases. For this reason, SWD is extremely important for the management of crop protection activities. In ... [more ▼]

Surface wetness duration (SWD) is an important factor influencing the occurrence of winter wheat diseases. For this reason, SWD is extremely important for the management of crop protection activities. In order to understand the SWD variability and its influence on winter wheat disease, the objective of this study was to (i) determine the sensitivity of our model on varying input plant parameters and (ii) to evaluate the influence of simulated SWD to meteorological variations in three different climatic regions of the Grand-Duchy of Luxembourg (EVERLANGE, OBERCORN and SCHIMPACH). In this work, an agrometeorological model known as the Surface Wetness Energy Balance (SWEB) was applied for the simulation of SWD. The model was previously applied in another study for winter wheat cultivars and was adapted for use with agrometeorological data easily available from standard meteorological monitoring stations. Based on weather data and simulated SWD data, sensitivity analyses were performed to compare the effects of relative humidity, air temperature, wind speed and net radiation on wetness duration over one growing season (March-July) at three test sites. The results indicated that the sensitivities were very similar at three sites and there was no spatial trend (i.e. difference between locations) in the sensitivities. However, the model is most sensitive to relative humidity and differences between 0.5 and 25 h (per month) SWD were found when increasing/decreasing relative humidity by 10%. The model was least sensitive to changes in air temperature, showing differences of only 0.5–2 h (per month) in SWD. Intermediate sensitivity is found for rainfall, net radiation and wind speed. Among the input plant parameters values, SWD was most sensitive to the maximum fraction of canopy allowed as wet surface area, leaf area index, maximum water storage per unit area and least sensitive to crop height. The sensitivity to parameter values was less important compared to the sensitivity to the meteorological variable relative humidity. [less ▲]

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See detailSensitivity of simulated surface wetness duration to meteorological variations in three different regions of the Grand-Duchy of Luxembourg
Mahtour, Abdeslam; El Jarroudi, Moussa ULg; Hoffmann, Lucien et al

Poster (2010, November 22)

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See detailRouille brune du blé, un modèle pour évaluer les risques
El Jarroudi, Moussa ULg; Giraud, Frédéric; Tychon, Bernard ULg et al

in Phytoma-la défense des végétaux (2010), 637

L’article présente un outil de prévision de la rouille brune au G.-D. de Luxembourg. De 2000 à 2003, cette maladie apparaissait à la fin de l’épiaison, mais depuis 2003, elle apparaît de plus en plus tôt ... [more ▼]

L’article présente un outil de prévision de la rouille brune au G.-D. de Luxembourg. De 2000 à 2003, cette maladie apparaissait à la fin de l’épiaison, mais depuis 2003, elle apparaît de plus en plus tôt (GS45 stade gonflement). Cette apparition précoce est probablement liée à des températures printanières supérieures par rapport à la normale 1971-2000. Une analyse des données météorologiques nocturnes et des données d’observation de la maladie sur quatre sites expérimentaux (Everlange, Christnach, Burmerange et Reuler) entre 2000 et 2003 a révélé une forte corrélation positive entre la prédiction de la maladie basée sur le critère d’au moins 12 heures consécutives avec une température comprise entre 8 et 16°C et une humidité supérieure à 60% et la maladie observée sur la F1 (R = 0.93 ; P < 0.05) et sur la F2 (R = 0.87 ; P < 0.05). Les sorties de ce modèle qui a été développé sur base d’une approche stochastique ont été utilisées dans les bulletins d’avertissements diffusés conjointement par le Centre de Recherche Public – Gabriel Lippmann et l’Université de Liège-Campus d’Arlon à partir de 2004. La mise en application de ce modèle a montré un taux de réussite oscillant entre 80 et 85% pour la simulation de la rouille brune au G.-D. de Luxembourg. L’effort se poursuit pour spatialiser les sorties du modèle sur tout le territoire luxembourgeois et faciliter son utilisation par tous les vulgarisateurs agricoles. [less ▲]

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See detailKnowledge-based approaches for degradation mapping in arid rangeland
Mahyou, Hamid ULg; Tychon, Bernard ULg; balaghi, Riad

Poster (2010, September 28)

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See detailBulletin agrométéorologique - Situation au 1er septembre 2010
Tychon, Bernard ULg; Djaby, Bakary ULg; Denis, Antoine ULg et al

in Bulletin Agrométéorologique (2010), 8(4), 1-4

La période d’avril à août 2010 fut marquée par une forte alternance de périodes sèches et humides avec des épisodes froids succédant à des vagues de chaleur. La période sèche de mi-juin à mi-juillet fut ... [more ▼]

La période d’avril à août 2010 fut marquée par une forte alternance de périodes sèches et humides avec des épisodes froids succédant à des vagues de chaleur. La période sèche de mi-juin à mi-juillet fut particulièrement remarquable et la fin de cette période s’est accompagnée de températures très élevées accentuant encore les besoins en eau des plantes. Les cultures à système racinaire superficiel ou situées dans des terrains peu profond ont largement souffert de cette période. Cependant le mois d’août très pluvieux a permis à la plupart des cultures de printemps de récupérer leur retard de croissance. Les rendements prévus par nos modèles sont bons pour les cultures de betterave sucrière, pomme de terre et maïs. [less ▲]

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See detailWheat Yield Estimates at NUTS-3 level using MODIS data: an approach based on the decreasing curves of green area index temporal profiles
Kouadio, Amani Louis ULg; Duveiller, Gregory; Djaby, Bakary ULg et al

in Cawkwell, Fiona (Ed.) Proceedings of RSPSoc2010 Annual Conference. 1st-3rd September 2010, Cork, Ireland (Nottingham: RSPSoc) (2010, September)

Wheat is the most widely-grown food crop in the world and the most important cereal crop traded on international markets. An early prediction of its yield prior to harvest at regional, national and ... [more ▼]

Wheat is the most widely-grown food crop in the world and the most important cereal crop traded on international markets. An early prediction of its yield prior to harvest at regional, national and international scales can play a crucial role in global markets, policy and decision making. Many models for yield forecasting are available with varying levels of complexity and empiricism. The use of remote sensing technology for monitoring crop condition and predicting crop yields at regional scales have been studied extensively during these last decades. Earth observation data, owing to their synoptic, timely and repetitive coverage, have been recognized as a valuable tool for yield and production forecasting. At field level, studies on crop breeding showed that a close correlation exists between green leaf area during maturation and grain yield in wheat. Thus, the onset and rate of senescence appeared as important factors for determining grain yield of this crop. The aim of this research is to explore a simplified approach for wheat yield forecasting at the European NUTS-3 administrative level, based on metrics derived from the senescence phase of green area index (GAI) estimated from remote sensing data. This study takes advantage of considerable recent improvements in sensor technology and data availability through the opportunity of applying medium/coarse spatial resolution data for deriving crop specific GAI time series by selecting pixels whose ground-projected instantaneous field of view is constituted by a high cover fraction of winter wheat. This approach is tested on 2 crop growing season over a 300 by 300 km study site comprising Belgium and northern France within the framework of the GLOBAM (GLObal Agricultural Monitoring systems by integration of earth observation and modelling techniques) project. The validation of such an approach will involve the comparison with official wheat yield data at NUTS-3 level. [less ▲]

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See detailModelling plant diseases impact with the Belgium Crop Growth Monitoring System.
El Jarroudi, Moussa ULg; Kouadio, Amani Louis ULg; Martin, Bertrand ULg et al

in Wery, Jacque; Shili-Touzi, I.; Perrin, A. (Eds.) PROCEEDING OF AGRO2010 the XIth ESA Congress (2010, September)

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See detailTime spray strategies for Septoria Leaf Blotch disease progress on winter wheat: the use of forecasting model
El Jarroudi, Moussa ULg; Giraud, Frédéric; Delfosse, Philippe et al

Conference (2010, August 07)

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See detailBulletin agrométéorologique - Situation au 30 juin 2010
Tychon, Bernard ULg; Djaby, Bakary ULg; Denis, Antoine ULg et al

in Bulletin Agrométéorologique (2010), 8(2), 1-6

A la fin du mois de juin, les conditions météorologiques peuvent être qualifiées de globalement bonnes sur la plus grande partie du territoire belge. De bons rendements sont annoncés sans toutefois ... [more ▼]

A la fin du mois de juin, les conditions météorologiques peuvent être qualifiées de globalement bonnes sur la plus grande partie du territoire belge. De bons rendements sont annoncés sans toutefois atteindre les rendements exceptionnels comme ceux du blé de l’an dernier. Les analyses spatiales dérivées de la télédétection confirment cette tendance favorable tout en indiquant une hétérogénéité importante dans certaines régions du pays qui peut être mise sur le compte de précipitations orageuses localisées. Les conditions climatiques des prochaines semaines seront déterminantes pour conserver tous les bons potentiels de rendement des cultures et éviter que la situation ne se dégrade pour les zones à plus faible potentiel. [less ▲]

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See detailSpatial heterogeneity of leaf wetness duration in winter wheat canopy and its influence on plant disease epidemiology
Mahtour, Abdeslam ULg; El Jarroudi, Moussa ULg; Giraud et al

in Phytopathology (2010)

Leaf wetness duration (LWD) is an important factor influencing the occurrence of plant disease epidemiology. Despite considerable efforts to determine LWD, little attention has been given to study its ... [more ▼]

Leaf wetness duration (LWD) is an important factor influencing the occurrence of plant disease epidemiology. Despite considerable efforts to determine LWD, little attention has been given to study its variability within the canopy. The objective of this study was to evaluate its spatiotemporal variability in wheat fields in a heterogeneous landscape. The spatiotemporal variability of LWD was evaluated in a site close to Arlon (Belgium) during the period May to July 2006 and 2007. LWD measurements were made using a set of flat plate sensors deployed at five different distances from a 18 m high hedge (5, 10, 20, 50, 100 m). Each set of two sensors was placed horizontally close the flag leaf. In addition, we collected the amount of dew water that deposited on rigid epoxy plates placed next to each sensors. Experimental results showed that LWD measurements revealed substantial heterogeneity among sensor positions. LWD is longer for sensors closer to the hedge mainly because of its shadowing effect. 3 to 4 hours of difference was observed between sensors located at 5 m and those located at 100 m, and besides, a significant quantitative difference (p < 0.0001) of dew deposit was observed between area beside hedge and those placed at 100 m. In summary, this study provides new information on how wetness is distributed on wheat leaves according to the distance from a hedge. This leads to local microclimate conditions that will contribute to the disease spatial heterogeneity. [less ▲]

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See detailAssessment Of The Night Weather Parameters And Their Use In Forecasting Model Of Wheat Leaf Rust.
El Jarroudi, Moussa ULg; Giraud, Frédéric; Delfosse, Philippe et al

in Phytopathology (2010), (100), 32

A stochastic model was developed to predict the wheat leaf rust (Puccinia triticina Eriks.) severity (percentage of leaf area with symptoms showing uredinia) in four-replicated field experiments located ... [more ▼]

A stochastic model was developed to predict the wheat leaf rust (Puccinia triticina Eriks.) severity (percentage of leaf area with symptoms showing uredinia) in four-replicated field experiments located in three villages (Diekirch district: Reuler; Grevenmacher district: Burmerange and Christnach), representative of the different agroclimatological zones of Luxembourg. The model was elaborated by the analysis of the night weather and leaf rust incidence. Statistical validation using regression analysis reports a strong correlation between the number of hours with specific meteorological conditions and the percentage leaf area covered by brown rust lesions for the two upper and youngest leaves, which are mostly responsible for photosynthesis activity and assimilates production filling the grains. The development of the brown rust requires a period of at least twelve consecutive hours with temperatures between 8 and 16°C and a relative humidity (RH) greater than 60%, with optimal values lying between 12 and 16°C and RH greater than 80%. <br />During the 2004 to 2009 period, at four sites, the linear regression between simulated and observed values for Puccinia triticina was highly significant (P < 0.01) and R2 (coefficient of determination) explained 80 to 85% of the variability. Efforts are now being developed to better define thresholds for fungicide applications and to spatialize the outputs of the model over the entire Luxembourg territory. [less ▲]

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See detailTime spray strategies for Septoria leaf blotch disease progress on winter wheat: The use of forecasting model
El Jarroudi, Moussa ULg; Giraud, Frédéric; Delfosse, Philippe et al

in Phytopathology (2010), 100

A mechanistic model, PROCULTURE, for assessing in real time the risk of progression of Septoria tritici (teleomorph Mycosphaerella graminicola) on winter wheat (Triticum aestivum L.) was used in Grand ... [more ▼]

A mechanistic model, PROCULTURE, for assessing in real time the risk of progression of Septoria tritici (teleomorph Mycosphaerella graminicola) on winter wheat (Triticum aestivum L.) was used in Grand-Duchy of Luxemburg over 2003 to 2009 to simulate disease progression in the canopy at four-replicated field experiments located in three villages (Diekirch district: Reuler; Grevenmacher district: Burmerange and Christnach), representative of the different agroclimatological zones of Luxembourg. This model has been developed in order to guide field observations on the different leaf layers and to find the optimum time of fungicide spray in fields. The model provides information which explains disease progression on the upper leaves. The relationship between disease control by fungicides and yield loss varies from site-to-site and from season-to-season. A weekly PROCULTURE recalibration is routinely done using actual disease levels observed on site. On average, no spray of fungicides or only one application is required to control efficiently the septoria leaf blotch disease. The PROCULTURE forecasts have been validated to be correct in about 85% of all cases. The treatment defined with the simulation model over 2003 to 2009 gave an earning grain yield (80%) more than the other treatments tested and as important as the double treatment for Everlange, Christnach and Burmerange. At Reuler, over 2003 to 2009, treatments based on the Septoria risk simulation model were recommended only in 2007. The climatic conditions of this site tend to favour organic farming in this region where the evolution of the foliar disease is very weak. [less ▲]

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See detailOptimisation de l'utilisation des ressources en eau du bassin du Kou pour des usages agricoles
Traore, Farid ULg; Dembélé, Youssouf; Tychon, Bernard ULg

Scientific conference (2010, May 28)

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See detailBulletin agrométéorologique - Situation au 30 avril 2010
Tychon, Bernard ULg; Djaby, Bakary ULg; Denis, Antoine ULg et al

in Bulletin Agrométéorologique (2010), 8(1), 1-4

La période hivernale fut caractérisée par des températures inférieures aux moyennes des 20 dernières années. L’hiver fut également marqué par d’abondantes chutes de neige. Les sommes de températures ... [more ▼]

La période hivernale fut caractérisée par des températures inférieures aux moyennes des 20 dernières années. L’hiver fut également marqué par d’abondantes chutes de neige. Les sommes de températures calculées depuis le début du mois de janvier sont inférieures d’environ 170 degrés.jours par rapport à la situation moyenne, ce qui signifie un retard moyen des cultures d’une bonne semaine, voire davantage. Les images satellites montrent cependant que ce retard calculé à partir du cumul de températures serait en grande partie rattrapé fin avril. En dehors du retard phénologique calculé par une de nos deux méthodes, aucun autre élément agrométéorologique important n’est à signaler. Aucune prévision de rendement n’est faite à ce stade. [less ▲]

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See detailClimatological characteristics of NDVI time series: challenges and constraints
Horion, Stéphanie; Tychon, Bernard ULg; Cornet, Yves ULg

in Bulletin de la Société Géographique de Liège (2010), 54

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Low resolution satellite imagery is one of the main sources of ... [more ▼]

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Low resolution satellite imagery is one of the main sources of information. In this paper, we describe a strategy to improve the quality of 10-daily time series of Normalized Difference Vegetation Index derived from SPOT-VEGETATION. A specifi c methodology was also defi ned in order to identify optimal test sites for the analysis of climate control on intra-annual dynamic of croplands. Finally two cases studies are presented to illustrate this research and in particular the non linear relationship between NDVI and meteorological parameters during the growing season. [less ▲]

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See detailUtilisation des prises de vue aérienne à basse altitude pour le suivi des activités hydro-agricoles. Cas du bassin du Kou.
Wellens, J.; Diallo, M.; Dakouré, D. et al

Conference (2010, March)

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See detailPromouvoir des approches innovantes de recherche-développement en matière de GIRE au Burkina Faso.
Wellens, J.; Diallo, M.; Gardin, N. et al

Conference (2010, March)

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See detailRemote sensing assessement of irrigated areas extension in the Kou watershed
Traore, Farid ULg; Tychon, Bernard ULg

Scientific conference (2010, January 12)

The Kou watershed is a geographical space having important water resources, whose are used between: drinking water supply of Bobo-Dioulasso city (Burkina-Faso’s second most important city) and surrounding ... [more ▼]

The Kou watershed is a geographical space having important water resources, whose are used between: drinking water supply of Bobo-Dioulasso city (Burkina-Faso’s second most important city) and surrounding localities; agriculture through very important irrigated surfaces; industry; fauna and flora preservation, through a minimal sanitary debit guaranteed. Since some decades, one observes more and more increased pressure on Kou water resources. From an agricultural point of view, a comparative visual observation of irrigated surfaces during the years 1980 and during years 2000 shows an increase of surfaces. It would be then appropriate to establish a potential of irrigation of the set of available water resources in order to estimate maximal irrigable surfaces by water resources. Thus, this study has for goal the evaluation of Kou watershed irrigated zones surface, with the help of remote sensing. In order to facilitate irrigated zones detection, the study will focused on the period between January and June, where all cultures are irrigated with Kou watershed surface water and/or groundwater. The chosen methodology is images classification in order to extract irrigated zones surface. We had for this study a set of images and various data: Landsat-4 TM, Landsat-5 TM, Landsat-7 ETM+, SPOT 5, aerial views, agro meteorological data, cartographic data (GIS), data investigation reports, etc. Because of images various origins, we conducted images pretreatment that essentially consisted in image reflectance calibration. This operation appears to be indispensable when working with images from coming different sensors. Classification methods that we used are: a maximum likelihood classification, then a decision tree classification applied to images for which vegetation index (NDVI) has been calculated. The later classification method has been introduced in order to permit a better discrimination between natural vegetation and crops which can often react in similar spectral ranges. This method is based on threshold detection of vegetation classes. Classification methods used allowed us to estimate until a certain point irrigated surfaces, without having, however, a finer information. With 30 m spatial resolution images covering a survey zone with "reduced" to "mean" agricultural lands size, it is sometimes enough difficult to discern natural vegetation pixels from crop pixels. So, we should have considered mixed classes of pixels that strongly skewed our final results. The overall accuracy of our classifications are between 70% and 90%, with Kappa coefficients between 0.4 and 0.85. These Kappa coefficients our results between "tolerable" and "good". However, our evaluations seem to be near enough of those gotten by the means of hydro agricultural inventories led on the same zone. The committed mistakes remain in an interval of +/-20%. [less ▲]

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