References of "Tychon, Bernard"
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See detailSoil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy
Bartholomeus, Harm; Kooistra, Lammert; Stevens, Antoine et al

in International Journal of Applied Earth Observation and Geoinformation (2011), 13(1), 81-88

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping ... [more ▼]

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation. [less ▲]

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See detailPrévision des rendements agricoles. Guide d'utilisation.
Bronne, Charles-Emmanuel; Wellens, Joost ULg; Midekor, Akoly Agblévi et al

Learning material (2011)

Manuel présentant une méthode, développée par l'Université de Liège, de prévision de la production agricole. Cette méthode se base sur l'utilisation de différents programmes informatiques, et a pour but ... [more ▼]

Manuel présentant une méthode, développée par l'Université de Liège, de prévision de la production agricole. Cette méthode se base sur l'utilisation de différents programmes informatiques, et a pour but de prévoir le rendement agricole à partir de données météorologiques, agrométéorologiques, et NDVI (télédétecté). Elle est appliquée dans ce manuel sur les cultures du coton et du maïs au Burki Faso. [less ▲]

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See detailSite-specific Septoria Leaf Blotch Risk Assessment in Winter Wheat using Weather-Radar Rainfall Estimates
Mahtour, Abdeslam ULg; El Jarroudi, Moussa ULg; Delobbe, Laurent et al

in Plant Disease (2011), 10.1094/PDIS-07-10-0482

The Septoria leaf blotch prediction model PROCULTURE was used to assess the impact on simulated infection rates when using rainfall estimated by radar instead of rain gauge measurements. When comparing ... [more ▼]

The Septoria leaf blotch prediction model PROCULTURE was used to assess the impact on simulated infection rates when using rainfall estimated by radar instead of rain gauge measurements. When comparing infection events simulated by PROCULTURE using radar- and gauge-derived data, the probability of detection (PODs) of infection events was high (0.83 on average), and the false alarm ratio (FARs) of infection events was not negligible (0.24 on average). For most stations, FARso of infection events decreased to 0 and PODso increased (0.85 on average) when the model outputs for both datasets were compared against visual observations of disease symptoms. An analysis of 148 infection events over three years at four locations showed no significant difference in the number of infection events of simulations using either dataset, indicating that, for a given location, radar estimates were as reliable as rain gauges for predicting infection events. Radar also provided better estimates of rainfall occurrence over a continuous space than weather station networks. The high spatial resolution provides radar with an important advantage that could significantly improve existing warning systems. [less ▲]

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See detailRegional-based typology of the main fungal diseases affecting winter wheat in the Grand-Duchy of Luxembourg
El Jarroudi, Moussa ULg; Giraud, Frédéric; Delfosse, Philippe et al

in Phytopathology (2011), 101

Despite its small territory size, the Grand-Duchy of Luxembourg (GDL) has several microclimates that result in a variability of disease severity between the South (Gutland) and the North (Oesling ... [more ▼]

Despite its small territory size, the Grand-Duchy of Luxembourg (GDL) has several microclimates that result in a variability of disease severity between the South (Gutland) and the North (Oesling). Septoria leaf blotch disease of wheat is an important disease in the GDL. Over 2003–2009, the severity was strong in Gutland (51% on average over the last two upper leaves at the late milk growth stage) and low in the Oesling (16% for the same leaves). For the years 2006, 2008 and 2009, the disease severity was less than 6% in the Oesling while it exceeded 40% in the Gutland. The second fungal disease that has become economically important is the wheat leaf rust. Over the same period, the Gutland and the Oesling showed consistently the highest and lowest disease severity respectively. In 2003 and 2007, the Gutland showed the highest disease severity with 66% and 57% respectively, whereas the lowest severity (<1%) was observed in the Oesling. Another important disease is wheat powdery mildew. The 2003 and 2009 cropping seasons showed the highest disease severity with 15% and 40%, respectively, in the Oesling whereas less than 1% severity was registered in the Gutland. Fusarium head blight was also present in the eastern part of the Gutland showing the highest prevalence and severity in 2007 and 2008 (8.5% and 8.3% respectively). These prevalence and severity percentages were significantly higher compared to the Oesling (% prevalence % severity, p = 0.049 and p = 0.012, respectively, Tukey’s test). [less ▲]

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See detailSITE – SPECIFIC MONITORING FOR DISEASE FORECASTING IN WINTER WHEAT.
El Jarroudi, Moussa ULg; Giraud, Frédéric; Delfosse, Philippe et al

in Journal of Plant Pathology [=JPP] (2011), 93(Supplement 1), 19-20

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See detailFirst report of the breakdown of the YR17 resistance gene to wheat stripe rust in the Grand Duchy of Luxembourg
El Jarroudi, Moussa ULg; Giraud, Frédéric; Tychon, Bernard ULg et al

in Journal of Plant Pathology [=JPP] (2011), 93(1), 243

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See detailDune rehabilitation using a mechanical fixation technique : effect on sediment fluxes and on the quantitative and qualitative recovery of the herbaceous groundcover.
Tidjani, Adamou Didier; Bielders, Charles; Ambouta, Karimou et al

in Geophysical Research Abstracts (2011)

This research shows the potentialities of mechanical windbreaks to rapidly stabilize dunes in the north sahelian area (Niger) thanks to the recovery of herbaceous groundcover.

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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 <br />epidemiology. Despite considerable efforts to determine LWD, little attention has been given to <br ... [more ▼]

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