References of "Destain, Marie-France"
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See detailExamining wheat yield sensitivity to temperature and precipitation changes for a large ensemble of crop models using impact response surfaces"
Pirttioja, N.; Fronzek, S.; Bindi, Marco et al

in Rotter, Reimund; Ewert, Frank (Eds.) Modelling climate change impacts on crop production for food security - Abstract book (2014, February)

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See detailBayesian methods for predicting and modelling winter wheat biomass
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

Poster (2014, February)

The objectives of this paper are threefold. The first objective is to propose to use an Improved Particle Filtering (IPF) based on minimizing Kullback-Leibler divergence for crop models' predictions. The ... [more ▼]

The objectives of this paper are threefold. The first objective is to propose to use an Improved Particle Filtering (IPF) based on minimizing Kullback-Leibler divergence for crop models' predictions. The performances of the proposed technique are compared with those of the conventional Particle Filtering (PF) for improving nonlinear crop model predictions. The main novelty of this task is to develop a Bayesian algorithm for nonlinear and non-Gaussian state and parameter estimation with better proposal distribution. The second objective is to investigate the effects of practical challenges on the performances of state estimation algorithms PF and IPF. Such practical challenges include (i) the effect of measurement noise on the estimation performances and (ii) the number of states and parameters to be estimated. The third objective is to use the state estimation techniques PF and IPF for updating prediction of nonlinear crop model in order to predict winter wheat biomass. PF and IPF are applied at a dynamic crop model with the aim to predict a state variable, namely the winter wheat biomass, and to estimate several model parameters. Furthermore, the effect of measurement noise (e.g., different signal-to-noise ratios) on the performances of PF and IPF is investigated. The results of the comparative studies show that the IPF provides a significant improvement over the PF because, unlike the PF which depends on the choice of sampling distribution used to estimate the posterior distribution, the IPF yields an optimum choice of the sampling distribution, which also accounts for the observed data. [less ▲]

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See detailParameter identification of the STICS crop model, using an accelerated formal MCMC approach
Dumont, Benjamin ULg; Leemans, Vincent ULg; Mansouri, Majdi ULg et al

in Environmental Modelling & Software (2014), 52

This study presents a Bayesian approach for the parameters’ identification of the STICS crop model based on the recently developed Differential Evolution Adaptive Metropolis (DREAM) algorithm. The ... [more ▼]

This study presents a Bayesian approach for the parameters’ identification of the STICS crop model based on the recently developed Differential Evolution Adaptive Metropolis (DREAM) algorithm. The posterior distributions of nine specific crop parameters of the STICS model were sampled with the aim to improve the growth simulations of a winter wheat (Triticum aestivum L.) culture. The results obtained with the DREAM algorithm were initially compared to those obtained with a Nelder-Mead Simplex algorithm embedded within the OptimiSTICS package. Then, three types of likelihood functions implemented within the DREAM algorithm were compared, namely the standard least square, the weighted least square, and a transformed likelihood function that makes explicit use of the coefficient of variation (CV). The results showed that the proposed CV likelihood function allowed taking into account both noise on measurements and heteroscedasticity which are regularly encountered in crop modelling [less ▲]

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See detailPredicting Winter Wheat Biomass And Grain Protein Content
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

in Proceedings of the 12th International Conference on Precision Agriculture (2014)

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See detailAssessing the potential of an algorithm based on mean climatic data to predict wheat yield
Dumont, Benjamin ULg; Leemans, Vincent ULg; Ferrandis, Salvador et al

in Precision Agriculture (2014), 15(3)

The real-time non-invasive determination of crop biomass and yield prediction is one of the major challenges in agriculture. An interesting approach lies in using process-based crop yield models in ... [more ▼]

The real-time non-invasive determination of crop biomass and yield prediction is one of the major challenges in agriculture. An interesting approach lies in using process-based crop yield models in combination with real-time monitoring of the input climatic data of these models, but unknown future weather remains the main obstacle to reliable yield prediction. Since accurate weather forecasts can be made only a short time in advance, much information can be derived from analyzing past weather data. This paper presents a methodology that addresses the problem of unknown future weather by using a daily mean climatic database, based exclusively on available past measurements. It involves building climate matrix ensembles, combining different time ranges of projected mean climate data and real measured weather data originating from the historical database or from real-time measurements performed in the field. Used as an input for the STICS crop model, the datasets thus computed were used to perform statistical within-season biomass and yield prediction. This work demonstrated that a reliable predictive delay of 3-4 weeks could be obtained. In combination with a local micrometeorological station that monitors climate data in real-time, the approach also enabled us to (i) predict potential yield at the local level, (ii) detect stress occurrence and (iii) quantify yield loss (or gain) drawing on real monitored climatic conditions of the previous few days. [less ▲]

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See detailNitrogen fertilisation recommendations : could they be improved using stochastically generated climates in conjunction with crop models ?
Dumont, Benjamin ULg; Basso, Bruno; Meza Morales, Walter ULg et al

in Proceedings of the 12th ICPA (2014)

Accurate determination of optimal Nitrogen (N) recommendations which ensure maximization of farmer's revenue while minimizing the environmental constraint is maybe among the major challenges in ... [more ▼]

Accurate determination of optimal Nitrogen (N) recommendations which ensure maximization of farmer's revenue while minimizing the environmental constraint is maybe among the major challenges in agriculture. Crop models have the potential to deal with such aspects and could thus be used to develop decision support systems. However unknown future weather conditions remains the key point of accurate yield forecast. This paper presents the results of a preliminary study that aims to supply the unknown future with stochastically generated climatic conditions. Coupling the methodology with appropriate decision rules led to a generic decision support system able to guide the N management practices. [less ▲]

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See detailLa compaction des sols agricoles en Wallonie
Destain, Marie-France ULg

Book published by SPW (2014)

Dans nos pays industrialisés, l’agriculture fait appel à des machines de plus en plus lourdes. Lorsque des charges élevées sont appliquées sur des sols sensibles, une compaction du sol peut se produire ... [more ▼]

Dans nos pays industrialisés, l’agriculture fait appel à des machines de plus en plus lourdes. Lorsque des charges élevées sont appliquées sur des sols sensibles, une compaction du sol peut se produire conduisant à des diminutions de rendements suite aux difficultés que rencontrent les racines pour prélever l’eau et les nutriments et à la perturbation de l’activité de la pédofaune. Au niveau environnemental, du fait de la compaction, l’infiltration de l’eau dans le sol est réduite, principalement dans l’horizon superficiel. Une accumulation de l’eau à la surface du sol avec un accroissement des écoulements latéraux et du ruissellement peut apparaître. Il en résulte une augmentation des risques d’inondation et de pollution de surface provenant de l’application d’intrants. Le risque d’érosion sur des sols en pente, même faible, est également accru. En Europe, on estime que 32 % des couches profondes de sol sont largement dégradées. A l’inverse de l’érosion ou de la salinisation qui montrent des signes visibles de dégradation, les effets néfastes de la compaction ne sont pas immédiatement perceptibles. Du fait que la compaction des horizons profonds (au-delà de 30 cm) est un phénomène difficilement réversible par régénération naturelle et que les méthodes de restauration artificielles ne sont pas toujours couronnées de succès, l’Union Européenne considère la compaction comme l’un des facteurs majeurs de la dégradation physique des sols. Le projet de Directive européenne COM(2006)232 amendé par la note 16157/07 du 14 décembre 2007 établit un cadre général pour la protection des sols. Ce projet prévoit notamment que les Etats membres, dont fait partie la Belgique, identifient sur leur territoire les zones susceptibles de présenter des processus de dégradation du sol (érosion, perte de matière organique, compaction, salinisation, contamination et perte de biodiversité). Une fois les zones à risque identifiées, les Etats membres doivent proposer des objectifs de réduction des risques ainsi que des mesures concrètes permettant de les atteindre. Ils sont libres de fixer leurs propres objectifs et de décider comment et quand les atteindre. Le projet SoCo a établi une cartographie de la sensibilité des sols européens à la compaction. Cependant, étant donné sa faible résolution, cette carte ne permet pas de se faire une idée précise de la situation en Wallonie. La Direction générale opérationnelle Agriculture, Ressources naturelles et Environnement du SPW a donc décidé de mettre en œuvre une étude pour analyser de manière plus précise les risques de compaction des sols en Wallonie. [less ▲]

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See detailLa compaction des sols forestiers en Wallonie
Destain, Marie-France ULg

Book published by SPW (2014)

Dans nos pays industrialisés, l’exploitation forestière fait appel à des machines de plus en plus lourdes pour assurer la vidange des coupes et le débardage des grumes. Lorsque des charges élevées sont ... [more ▼]

Dans nos pays industrialisés, l’exploitation forestière fait appel à des machines de plus en plus lourdes pour assurer la vidange des coupes et le débardage des grumes. Lorsque des charges élevées sont appliquées sur des sols sensibles, une compaction du sol peut se produire entraînant une réduction de porosité, avec des conséquences néfastes sur la vitalité des peuplements. Au niveau environnemental, du fait de la compaction, l’infiltration de l’eau dans le sol est réduite, principalement dans l’horizon superficiel. Une accumulation de l’eau à la surface du sol avec un accroissement des écoulements latéraux et du ruissellement peut apparaître. Il en résulte une augmentation des risques d’inondation et de pollution de surface provenant de l’application d’intrants. Le risque d’érosion sur des sols en pente, même faible, est également accru. En Europe, on estime que 32 % des couches profondes de sol sont largement dégradées. A l’inverse de l’érosion ou de la salinisation qui montrent des signes visibles de dégradation, les effets néfastes de la compaction ne sont pas immédiatement perceptibles. Du fait que la compaction des horizons profonds (au-delà de 30 cm) est un phénomène difficilement réversible par régénération naturelle et que les méthodes de restauration artificielles ne sont pas toujours couronnées de succès, l’Union Européenne considère la compaction comme l’un des facteurs majeurs de la dégradation physique des sols. Le projet de Directive européenne COM(2006)232 amendé par la note 16157/07 du 14 décembre 2007 établit un cadre général pour la protection des sols. Ce projet prévoit notamment que les Etats membres, dont fait partie la Belgique, identifient sur leur territoire les zones susceptibles de présenter des processus de dégradation du sol (érosion, perte de matière organique, compaction, salinisation, contamination et perte de biodiversité). Une fois les zones à risque identifiées, les Etats membres doivent proposer des objectifs de réduction des risques ainsi que des mesures concrètes permettant de les atteindre. Ils sont libres de fixer leurs propres objectifs et de décider comment et quand les atteindre. Le projet SoCo a établi une cartographie de la sensibilité des sols européens à la compaction. Cependant, étant donné sa faible résolution, cette carte ne permet pas de se faire une idée précise de la situation en Wallonie. Par ailleurs, le Code Forestier Wallon entré en vigueur le 13 septembre 2008 prévoit explicitement l’interdiction d’occasionner des dégâts au sol qui pourraient avoir des conséquences à long terme sur la vitalité des peuplements. Dans ce cadre, la Direction générale opérationnelle Agriculture, Ressources naturelles et Environnement du SPW a décidé de mettre en œuvre une étude pour analyser de manière plus précise les risques de compaction des sols en Wallonie. [less ▲]

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See detailBayesian methods for predicting LAI and soil water content
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Leemans, Vincent ULg et al

in Precision Agriculture (2014), 15(2), 184-201

LAI of winter wheat (Triticum aestivum L.) and soil water content of the topsoil (200 mm) and of the subsoil (500 mm) were considered as state variables of a dynamic soil-crop system. This system was ... [more ▼]

LAI of winter wheat (Triticum aestivum L.) and soil water content of the topsoil (200 mm) and of the subsoil (500 mm) were considered as state variables of a dynamic soil-crop system. This system was assumed to progress according to a Bayesian probabilistic state space model, in which real values of LAI and soil water content were daily introduced in order to correct the model trajectory and reach better future evolution. The chosen crop model was mini STICS which can reduce the computing and execution times while ensuring the robustness of data processing and estimation. To predict simultaneously state variables and model parameters in this non-linear environment, three techniques were used: Extended Kalman Filtering (EKF), Particle Filtering (PF), and Variational Filtering (VF). The significantly improved performance of the VF method when compared to EKF and PF is demonstrated. The variational filter has a low computational complexity and the convergence speed of states and parameters estimation can be adjusted independently. Detailed case studies demonstrated that the root mean square error (RMSE) of the three estimated states (LAI and soil water content of two soil layers) was smaller and that the convergence of all considered parameters was ensured when using VF. Assimilating measurements in a crop model allows accurate prediction of LAI and soil water content at a local scale. As these biophysical properties are key parameters in the crop-plant system characterization, the system has the potential to be used in precision farming to aid farmers and decision makers in developing strategies for site-specific management of inputs, such as fertilizers and water irrigation. [less ▲]

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See detailULTRASONIC WAVES THROUGH AGRICULTURAL SOILS TO DETERMINE THEIR COMPACTION AND POROSITY LEVEL 
Luong, Jeanne ULg; Mercatoris, Benoît ULg; Destain, Marie-France ULg

Poster (2014)

Compaction is one of the major causes of the physical degradation of agricultural soils. The traffic of more and more heavy machines leads to a decrease of the porosity at both the topsoil and subsoil ... [more ▼]

Compaction is one of the major causes of the physical degradation of agricultural soils. The traffic of more and more heavy machines leads to a decrease of the porosity at both the topsoil and subsoil levels. This has negative impacts in agricultural and environmental contexts such as the reduction of soil fertility and water infiltration. This project aims at characterizing in a fast and non-destructive way the state of compaction of an agricultural soil at a local scale using ultrasonic wave propagation. Acoustic signatures of soil samples will be correlated to their compaction level and their porosity distribution. This should allow a better comprehension of the compaction process and help to define critical threshold. As a result, this methodology could assist in taking restrictive measures such as load limitation of agricultural engines and implementing remedial methods. This poster presents the experimental protocol implement for this research. [less ▲]

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See detailASSESSMENT OF PLANT LEAF AREA MEASUREMENT BY USING STEREO- VISION
Leemans, Vincent ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

in 2013 International Conference on 3D Imaging (IC3D) - Proceedings (2013, December)

The aim of this study is to develop an alternative measurement for the leaf area index (LAI), an important agronomic parameter for plant growth assessment. A 3D stereo-vision technique was developed to ... [more ▼]

The aim of this study is to develop an alternative measurement for the leaf area index (LAI), an important agronomic parameter for plant growth assessment. A 3D stereo-vision technique was developed to measure both leaf area and corresponding ground area. The leaf area was based on pixel related measurements while the ground area was based on the mean distance from the leaves to the camera. Laboratory and field experiments were undertaken to estimate the accuracy and the precision of the technique. Result showed that, though the leaves-camera distance had to be estimated precisely in order to have accurate measurement, the precision of the LAI evaluation, after regression, was equivalent to the reference measurements, that is to say around 10% of the estimated value. This shows the potential of the 3D measurements compared with tedious reference measurements. [less ▲]

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See detailA comparison of within-season yield prediction methodologies
Dumont, Benjamin ULg; Basso, Bruno; Bodson, Bernard ULg et al

Conference (2013, November)

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See detailLeaf area and leaf orientation measurement by using stereo-vision
Leemans, Vincent ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

Conference (2013, September 03)

This paper presents a 3D stereo-vision system aiming at the measurement of plant characteristics. The method is intended to be used in an Ecotron where the availability of plant material is limited and ... [more ▼]

This paper presents a 3D stereo-vision system aiming at the measurement of plant characteristics. The method is intended to be used in an Ecotron where the availability of plant material is limited and where crop should be characterised non destructively. The plants were not considered as individuals, it was the crop as a whole that was characterised. The leaf area index (LAI) was measured. It is an important property of vegetation, since it determines the photosynthetic primary production, the plant evaporation and characterises the plant growth. The average leaf angle (ALA) was also measured. For the computation, leaf pixels were differentiated from soil pixels by using linear discriminant analysis. The stereo vision system computed the distance to the camera of each pixel in the image in the region where the pixels are present in both images. The observed area was computed on the basis of the average distance of the leaf pixels in the region. The leaf area was evaluated for each triplet of adjacent pixels by computing the cross product of the vectors defined by those three points. The sum gave the leaf area for the same region. The area of these triangles was summed for all the pixels in the region and the ratio to the observed area gave the LAI. The ALA was the mean orientation of the pixel triplets. After calibration, the method was found to present a coefficient of correlation of 0.93 with destructive reference measurements and a precision of 0.12 for the LAI. It was possible to measure the LAI and the ALA from the germination up to the ripening stage with a minimum of work load. [less ▲]

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See detailYield variability linked to climate uncertainty and nitrogen fertilisation
Dumont, Benjamin ULg; Basso, Bruno; Leemans, Vincent ULg et al

in Stafford, John V. (Ed.) Precision agriculture '13 (2013, July)

At the parcel scale, crop models such as STICS are powerful tools to study the effects of variable inputs such as management practices (e.g. nitrogen (N) fertilisation). In combination with a weather ... [more ▼]

At the parcel scale, crop models such as STICS are powerful tools to study the effects of variable inputs such as management practices (e.g. nitrogen (N) fertilisation). In combination with a weather generator, we built up a general methodology that allows studying the yield variability linked to climate uncertainty, in order to assess the best N practice. Our study highlighted that, applying the Belgian farmer current N practice (60 60 60 kgN.ha-1), the yield distribution was found to be very asymmetric with a skewness of -1.02 and a difference of 5% between the mean (10.5 t.ha-1) and the median (11.05 t.ha-1) of the distribution. Which implied that, under such practice, the probability for farmers to achieve decent yields, in comparison of the mean of the distribution, was the highest. [less ▲]

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See detailPrediction of non-linear time-variant dynamic crop model using bayesian methods
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

in John Stafford (Ed.) Precision agriculture '13 (2013, July)

This work addresses the problem of predicting a non-linear time-variant leaf area index and soil moisture model (LSM) using state estimation. These techniques include the extended Kalman filter (EKF ... [more ▼]

This work addresses the problem of predicting a non-linear time-variant leaf area index and soil moisture model (LSM) using state estimation. These techniques include the extended Kalman filter (EKF), particle filter (PF) and the more recently developed technique, variational filter (VF). In the comparative study, the state variables (the leaf-area index LAI, the volumetric water content of the layer 1, HUR1 and the volumetric water content of the layer 2, HUR2) are estimated from noisy measurements of these variables, and the various estimation techniques are compared by computing the estimation root mean square error with respect to the noise-free data. The results show that VF provides a significant improvement over EKF and PF. [less ▲]

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