Satellite remote sensing priorities for better assimilation in crop growth models : winter wheat LAI and grassland mowing dates case studies

In a context of markets globalization, early, reliable and timely estimations of crop yields at regional to global scale are clearly needed for managing large agricultural lands, determining food pricing and trading policies but also for early warning of harvest shortfalls. Crop growth models are often used to estimate yields within the growing season. The uncertainties associated with these models contribute to the uncertainty of crop yield estimations and forecasts. Satellite remote sensing, through its ability to provide synoptic information on growth conditions over large geographic extents and in near real-time, is a key data source used to reduce uncertainties in biophysical models through data assimilation methods. This thesis aims at assessing possible improvements for the assimilation of remotely-sensed biophysical variables in crop growth models and to estimate their related errors reduction on modelled yield estimates. Assimilated observations are winter wheat leaf area index (LAI) and grassland mowing dates derived respectively from optical (MODIS) and microwave (ERS-2) data. These observations have been assimilated in WOFOST and LINGRA growth models. Observing System Simulation Experiments (OSSE) allowed assessing errors reduction on yield estimates after assimilation for different situations of accuracy and frequency of remotely-sensed estimates and for different assimilation strategies, indicating expected improvements with the currently available and forthcoming sensors; it supports also guidelines for future satellite missions. A main finding is the fact that yield estimate improvements are only possible for assimilation strategies able to correct the possible phenological discrepancies between the remotely-sensed and the simulated data. These phenological shifts arise mainly from uncertainties on the parameters and initial states driving the phenological stages in the models but are also due, in some situations, to lack of pixel purity because of the medium resolution of sensors such as MODIS. This thesis also identifies some of the main sources of uncertainties and assesses their impact on assimilation performances. The impact of water content and biomass on SAR backscattering of grasslands is specifically assessed. The backscattering of grasslands increases with the increases of water content and decreases with the biomass in dry conditions. Based on these results, methodologies to classify grasslands according to land use (mowing or grazing) and to detect mowings are designed and demonstrated. A good classification accuracy is observed (overall accuracy around 80%). Results for mowings detection are a bit lower as half of the mowings are correctly identified but the methodology can be considered as promising in particular in the perspective of very dense SAR time series as currently acquired operationally by Sentinel-1.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201

Bulletin agrométéorologique - Situation au 30 septembre 2007

Les conditions météorologiques depuis le 20 août dernier, date du dernier bulletin, ont été très proches des conditions normales. Mis à part quelques orages locaux, aucun phénomène météorologique particulier n’est à signaler. Les rendements satisfaisants à bons annoncés dans le dernier bulletin pour les cultures de maïs, betterave et pomme de terre sont confirmés

AquaCrop and the Belgian collaborative agriculture monitoring (BELCAM) platform

peer reviewe

Crop Phenology Modelling Using Proximal and Satellite Sensor Data

peer reviewedUnderstanding crop phenology is crucial for predicting crop yields and identifying potential risks to food security. The objective was to investigate the effectiveness of satellite sensor data, compared to field observations and proximal sensing, in detecting crop phenological stages. Time series data from 122 winter wheat, 99 silage maize, and 77 late potato fields were analyzed during 2015–2017. The spectral signals derived from Digital Hemispherical Photographs (DHP), Disaster Monitoring Constellation (DMC), and Sentinel-2 (S2) were crop-specific and sensor-independent. Models fitted to sensor-derived fAPAR (fraction of absorbed photosynthetically active radiation) demonstrated a higher goodness of fit as compared to fCover (fraction of vegetation cover), with the best model fits obtained for maize, followed by wheat and potato. S2-derived fAPAR showed decreasing variability as the growing season progressed. The use of a double sigmoid model fit allowed defining inflection points corresponding to stem elongation (upward sigmoid) and senescence (downward sigmoid), while the upward endpoint corresponded to canopy closure and the maximum values to flowering and fruit development. Furthermore, increasing the frequency of sensor revisits is beneficial for detecting short-duration crop phenological stages. The results have implications for data assimilation to improve crop yield forecasting and agri-environmental modeling

Modelling responses of forages to climate change with a focus on nutritive value

European livestock agriculture is extraordinarily diverse, and so are the challenges it faces. This diversity has contributed to the development of a fragmented set of research communities. As a result, livestock research is often under-represented at policy level, despite its high relevance for the environment and food security.Understanding livestock systems and how they can sustainably adapt to global change requires inputs across research areas, including grasslands, nutrition, health, welfare and ecology. It also requires experimental researchers, modellers and stakeholders to work closely together.Networks and capacity building structures are vital to enable livestock research to meet the challenges of climate change. They need to maintain shared resources and provide non-competitive arenas to share and synthesize results for policy support.  Long term strategic investment is needed to support such structures. Their leadership requires very different skills to those effective in scientific project coordination

Meteorological risks as drivers of environmental innovation in agro-ecosystem management

The extreme weather events, projected to increase both in frequency and magnitude with climate change have significant impact on agro-ecosystem services and pose severe limitations to sustainable agricultural land management. The proposed activities start from the hypothesis that these meteorological risks act as drivers of environmental innovation in agro-ecosystem management. These activities deal with risks associated with extreme weather phenomena and with risks of biological origin (e.g. pests and diseases). In order to reach this objective, the following elements of the chain of risk should be considered: • Hazard (assessment of the likely frequency and magnitude of extreme meteorological events)• Impact (analysis of the potential bio-physical and socio-economic impact of extreme weather events on agro-ecosystems)• Vulnerability (identification of the most vulnerable agro-ecosystems)• Risk Management (uncovering innovative risk management and adaptation options)These activities will concentrate on promoting a robust and flexible framework by demonstrating its performance across Belgian agro-ecosystems, and by ensuring its relevance to policy makers and practitioners. Impacts developed from physically based models will not only provide information on the state of the damage at any given time, but also assist in understanding the links between different factors causing damage and determining bio-physical vulnerability. Socio-economic impacts will enlarge the basis for vulnerability mapping, risk management and adaptation options. A strong expert and end-user network will be established to help exploiting project results to meet user need

Relative efficiency of alternative methods to evaluate wood stiffness in the frame of hybrid larch (Larix × eurolepis Henry) clonal selection

This study compares the efficiency of 3 indirect techniques that evaluate Young's modulus all along the sawing leading to the production of normalised specimens of hybrid larch trees from a clonal test. Ultrasonic speed is demonstrated as an interesting method for clone classification regarding Young's modulus in a clonal selection programme, whatever the sawing stage. However, the quality of results is reduced with standing tree measurements. The use of both the Pilodyn and resonance frequency measures is confirmed as a possibility.Efficacité relative de méthodes alternatives d'évaluation de la rigidité du bois de mélèze hybride (Larix × eurolepis Henry) dans le cadre d’une sélection clonale. L'efficacité relative de 3 techniques d'évaluation du module d'élasticité par voie indirecte a été testée sur différents types d'échantillons au cours des étapes de la découpe de mélèzes hybrides, issus d'un test clonal, depuis l'arbre debout jusqu'aux éprouvettes normalisées selon la norme NF B 51-016. Cette étude fait apparaître que la mesure de la vitesse ultrasonore s'avère une méthode satisfaisante de classement des clones pour le module d'élasticité dans le cadre d'un programme de sélection clonale, quel que soit le type d'échantillon utilisé. La qualité des résultats se réduit cependant avec l'augmentation de la taille des échantillons pour devenir minimale lorsque la mesure est réalisée sur arbre debout. Les résultats positifs des mesures à l'aide du Pilodyn, effectuées sur arbre debout, ainsi que les mesures de la fréquence de résonance, réalisées sur éprouvettes normalisées et barreaux, confirment et justifient l'intérêt qui leur est porté par de nombreux auteurs

Among and within provenance variability for decay resistance of Larch wood to fungi

Decay resistance of Larch wood was examined at the species, provenance and tree levels. To realise this study, 313 trees were harvested in 13 contrasting populations of different ages derived from 2 natural stands (France, Austria) and 4 provenance/progeny trials (Germany, Belgium, France and Great-Britain). The material includes 11 European, 1 japanese and 2 hybrid larch origins.Improvement of larch (Larix sp.) for better growth, stem form and wood qualit