References of "Garré, Sarah"
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See detailWater, essentieel voor de landbouwsector in Vlaanderen
Garré, Sarah ULiege

Conference given outside the academic context (2020)

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See detailWater and agriculture in a context of climate change
Garré, Sarah ULiege

Poster (2020, June 15)

If you want to know more about the role of water used for Flemish agriculture in the context of climate change, you've come to the right place. With this interactive poster I present the importance of ... [more ▼]

If you want to know more about the role of water used for Flemish agriculture in the context of climate change, you've come to the right place. With this interactive poster I present the importance of water in agriculture for today and tomorrow. How can Flemish agriculture adapt to the consequences of a changing climate on water availability and quality? What are the challenges and especially, what are possible solutions? [less ▲]

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See detailVARIABLE RATE IRRIGATION AND NITROGEN FERTILIZATION IN POTATO; ENGAGE THE SPATIAL VARIATION (POTENTIAL)
Garré, Sarah ULiege; Janssens, Pieter; Reynaert, Sofie et al

Report (2020)

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See detailHow do we obtain the data driving precision farming applications?
Garré, Sarah ULiege

Learning material (2020)

The interactive, digital lift-the-flap poster shows you which techniques are used to generate the data necessary for precision farming.

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See detailGeophysics for agriculture? To the roots! (invited talk RWTH Aachen)
Garré, Sarah ULiege

Scientific conference (2019, December 18)

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See detailGeophysics for agriculture? To the roots!
Garré, Sarah ULiege

Conference (2019, November 12)

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See detailCalibration, Conversion, and Quantitative Multi-Layer Inversion of Multi-Coil Rigid-Boom Electromagnetic Induction Data
Von Hebel, Christian ULiege; van der Kruk, Jan; Huisman, Johan A. et al

in Sensors (2019)

Multi-coil electromagnetic induction (EMI) systems induce magnetic fields below and above the subsurface. The resulting magnetic field is measured at multiple coils increasingly separated from the ... [more ▼]

Multi-coil electromagnetic induction (EMI) systems induce magnetic fields below and above the subsurface. The resulting magnetic field is measured at multiple coils increasingly separated from the transmitter in a rigid boom. This field relates to the subsurface apparent electrical conductivity (σa), and σa represents an average value for the depth range investigated with a specific coil separation and orientation. Multi-coil EMI data can be inverted to obtain layered bulk electrical conductivity models. However, above-ground stationary influences alter the signal and the inversion results can be unreliable. This study proposes an improved data processing chain, including EMI data calibration, conversion, and inversion. For the calibration of σa, three direct current resistivity techniques are compared: Electrical resistivity tomography with Dipole-Dipole and Schlumberger electrode arrays and vertical electrical soundings. All three methods obtained robust calibration results. The Dipole-Dipole-based calibration proved stable upon testing on different soil types. To further improve accuracy, we propose a non-linear exact EMI conversion to convert the magnetic field to σa. The complete processing workflow provides accurate and quantitative EMI data and the inversions reliable estimates of the intrinsic electrical conductivities. This improves the ability to combine EMI with, e.g., remote sensing, and the use of EMI for monitoring purposes. [less ▲]

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See detailImpact of Maize Roots on Soil–Root Electrical Conductivity: A Simulation Study
Sathyanarayan, Rao; Meunier, Félicien; Ehosioke, Solomon ULiege et al

in Vadose Zone Journal (2019)

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See detailUse of precision farming practices and crop modelling for enhancing water and phosphorus efficiency
El-Mejjaouy, Yousra ULiege; Mamassi, Achraf ULiege; Chtouki, Mohamed ULiege et al

Poster (2019, October 07)

In a context of climate change, African agriculture aims at developing new approaches to face multiple constraints related to water scarcity, soil degradation or nutrients depletion. Nonrenewable ... [more ▼]

In a context of climate change, African agriculture aims at developing new approaches to face multiple constraints related to water scarcity, soil degradation or nutrients depletion. Nonrenewable resources such as phosphorus are of concern. Precision farming, as a new alternative to conventional agriculture, aims to improve crop productivity through the optimization of water and nutrients use efficiency. It considers the spatiotemporal variability of fields related to soil heterogeneity, plant nutrient needs and meteorological conditions through the growing season. For an effective management of soil and crop system, several new technologies have emerged, including soil-plant sensing, innovative crop management practices, and crop growth simulation and yield forecasting models. Regarding phosphorus management, use efficiency can be improved through the accurate assessment of phosphorus status in soil and plant. Proximal sensing based on visible near-infrared spectroscopy seems to be a promising alternative to manage soil fertility, understand phosphorus dynamics and enhance crop productivity. These aims can be also achieved by adopting hyper-frequent drip fertigation as an efficient agricultural practice, combined to hydrogeophysics to monitor water and nutrient fluxes in the soil-plant continuum. In addition, based on the interactions between meteorological conditions, soil properties and crop management, the use of agrometeorological models in simulation of crop growth parameters and forecasting crop production levels may allow assessing soil fertility and potential, ensuring an optimal future exploitation of farmland through the improvement of fertilization practices in an integrated management cropping system. [less ▲]

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See detailGeo-phy-quoi?!
Garré, Sarah ULiege

Diverse speeche and writing (2019)

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See detailTwo-dimensional monitoring of soil water content in fields with plastic mulching using electrical resistivity tomography
Chen, Baoqin; Garré, Sarah ULiege; Liu, Haitao et al

in Computers and Electronics in Agriculture (2019), 159

Plastic mulching (PM) has become an important agricultural practice to improve crop yields worldwide, while there is still a lack of methods to quantify the complex spatial variations of soil water ... [more ▼]

Plastic mulching (PM) has become an important agricultural practice to improve crop yields worldwide, while there is still a lack of methods to quantify the complex spatial variations of soil water content (SWC) in the PM field. In this study, a methodology for using Electrical Resistivity Tomography (ERT) to get SWC information in the PM field was presented. Its performance in monitoring SWC was validated, and the spatial variation of SWC was analyzed using the ERT results. A simplified Waxman and Smits model was selected to calibrate the pedo-physical relationship, and it showed good performance (coefficient of determination > 0.92). With the calibrated model, the SWC obtained using ERT showed good agreement with soil moisture sensors in different soil layers (RMSE < 0.027 cm3 cm−3). The ERT results showed that rainfall and drying events have different effects on SWC at different growing stages. At the early stage, rainfall and drying events mainly influenced SWC on the bare strip, while at the later stage, rainfall and drying events had more obvious effects on the zone near the planting hole. On a seasonal scale, a higher SWC was not only found in the middle part of the mulched strip, but also in the bare strip, while a lower SWC was found in positions near the planting hole. At the same time, a high-resolution ERT measurement revealed that the SWC was also largely influenced by the soil heterogeneity. As such, SWC in the mulched strip was not necessarily higher than in the bare strip as we had supposed, but showed a high degree of irregularity in two dimensions. Considering the irregularity of SWC in two dimensions, our study calls for replacing point-scale measurement with two-dimensional monitoring methods when acquiring SWC information in a field with PM. [less ▲]

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See detailFunctional-structural root system model validation using soil MRI and tracer experiment
Koch, Axelle; Meunier, Félicien; Vanderborght, Jan et al

in Journal of Experimental Botany (2019)

Functional-structural root system models simulate the relations between root system architectural and hydraulic properties, and the spatio-temporal distributions of water and solute in the root zone. Such ... [more ▼]

Functional-structural root system models simulate the relations between root system architectural and hydraulic properties, and the spatio-temporal distributions of water and solute in the root zone. Such models might help identify optimal plant properties for breeding and contribute to increased water use efficiency. However, it must be first demonstrated that they accurately reproduce the processes they intend to describe. This is challenging because the flow and transport processes towards individual roots are hard to observe. We demonstrate how this deadlock could be broken by combining co-registered root and tracer distributions obtained from magnetic resonance imaging with a root system model in an inverse modeling scheme. The main features in the tracer distributions were well reproduced by the model using realistic root hydraulic parameters. By combining functional-structural root system model with 4D tracer observations, we were able to quantify the water uptake distribution of a growing root system. We showed that 76% of the transpiration was extracted through 3 rd order roots. The simulations also demonstrated that accurate water uptake distribution cannot be directly derived neither from observations of tracer accumulation nor from water depletion. However, detailed tracer experiments combined with process-based models help decipher mechanisms underlying root water uptake. [less ▲]

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See detailHow far can consumer grade UAV RGB imagery describe crop production? A 3D and multi-temporal modelling approach applied to Zea mays
Michez, Adrien ULiege; Bauwens, Sébastien ULiege; Brostaux, Yves ULiege et al

in Remote Sensing (2018), 10(11), 1798

In recent decades, remote sensing has increasingly been used to estimate the spatio-temporal evolution of crop biophysical parameters such as the above-ground biomass (AGB). On a local scale, the advent ... [more ▼]

In recent decades, remote sensing has increasingly been used to estimate the spatio-temporal evolution of crop biophysical parameters such as the above-ground biomass (AGB). On a local scale, the advent of unmanned aerial vehicles (UAVs) seems to be a promising trade-off between satellite/airborne and terrestrial remote sensing. This study aims to evaluate the potential of a low-cost UAV RGB solution to predict the final AGB of Zea mays. Besides evaluating the interest of 3D data and multitemporality, our study aims to answer operational questions such as when one should plan a combination of two UAV flights for AGB modeling. In this case, study, final AGB prediction model performance reached 0.55 (R-square) using only UAV information and 0.8 (R-square) when combining UAV information from a single flight with a single-field AGB measurement. The adding of UAV height information to the model improves the quality of the AGB prediction. Performing two flights provides almost systematically an improvement in AGB prediction ability in comparison to most single flights. Our study provides clear insight about how we can counter the low spectral resolution of consumer-grade RGB cameras using height information and multitemporality. Our results highlight the importance of the height information which can be derived from UAV data on one hand, and on the other hand, the lower relative importance of RGB spectral information. [less ▲]

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See detailThe ecotron as a surrogate for reality. Too good to be true? (invited talk)
Garré, Sarah ULiege; Longdoz, Bernard ULiege; Leemans, Vincent ULiege

Conference (2018, October 11)

Finding solutions to adapt to the impact of global change is still one of the most important challenges of the 21st century. While huge modelling advances have been made and experimental methods to study ... [more ▼]

Finding solutions to adapt to the impact of global change is still one of the most important challenges of the 21st century. While huge modelling advances have been made and experimental methods to study the earth system are diversifying, a major problem to find those solutions remains: the unclosed gap between spatial and temporal scales. Results from controlled experiments in pots or greenhouses are sometimes difficult to relate to observations at the field and landscape scale due to the complex interplay of various processes. In addition, it has been hard to reproduce the future effects of climate change experimentally, leading to an inevitable extrapolation of model predictions to zones where no validation is possible. Ecotrons provide unprecedented possibilities to study the soil-vegetation-microbiome-atmosphere continuum in highly controlled conditions and this under any climate scenario of interest. In this presentation, we will present the new Ecotron facility of the TERRA Research Center in Gembloux, Belgium designed to submit six mesocosms (small ecosystems) installed on lysimeters (2m² X 1,5m), to any climatic conditions desired and see how it can reproduce (or not) the current and future in-nature reality. In addition to the controlled variables, instrumentation is set up to monitor energy and water budget and ecosystem functions (yield and production quality, GHG mitigation and C storage, water retention capacity and leaching quality, soil fertility,…) In the first experiment planned, we will compare the behavior of winter wheat plots submitted to present and future climatic conditions. The present conditions will mimic the situation already recorded on the Lonzee ICOS site. The future scenario will represent a typical year of the 2050-2070 period (drift of the mean annual value and increase of the temporal variabiity) and chosen for its ability to produce a contrasting crop yield. The results will also give us information about the ability of ecotrons to reproduce a realistic ecosystem functionning and expose which aspects of plant growth and soil behavior are well and not well reproduced in the artificially generated climatic conditions. This phase is essential to demonstrate the actual potential and shortcomings of this cross-cutting research infrastructure [less ▲]

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See detailUse and challenges of electrical resistivity tomography to study processes in agro-ecosystems
Garré, Sarah ULiege; Javaux, Mathie; Manhaeghe, Thibault et al

Scientific conference (2018, September 25)

Sustainable management of agro-ecosystems requires a thorough understanding of the interaction between physical, chemical and biological processes at play. In addition, processes at pore scale are linked ... [more ▼]

Sustainable management of agro-ecosystems requires a thorough understanding of the interaction between physical, chemical and biological processes at play. In addition, processes at pore scale are linked to field scale phenomena, but this connection is often poorly understood. Electrical resistivity tomography (ERT) is increasingly used in the context of agriculture since the measured resistivity distribution can be linked to soil moisture, soil structural characteristics or pore water salinity. Due to its minimally invasive character, its spatial coverage and its monitoring abilities, ERT can be used to study field heterogeneity and competition between plants, quantify water fluxes throughout a growing season or distinguish preferential flow pathways in soils. Is resolution is well-below classical soil imaging techniques such as X-ray CT or MRI, but its spatial coverage much larger. This highlights the potential of ERT to link our knowledge obtained from pore scale data to field scale processes. Nevertheless, a lot of challenges still remain. A Tikhonov-type regularization approach is often used to solve the ill-posed, inverse problem linked to ERT, resulting in a smoothed resistivity distribution. However, in reality strong contrasts can exist due to e.g. compacted soil layers due to ploughing, water infiltration fronts, etc. and in that case other operators have been proposed to regularize the inversion. Taking into account spatial heterogeneity of petrophysical characteristics and providing a realistic uncertainty estimation are additional challenges, which can be addressed using stochastic approaches. Monitoring data provides further elements to constrain the inverse problem: data can be replaced by data difference and regularization may incorporate the temporal dimension for instance. However, such constraints require their compatibility with the studied temporal process, which is not always straightforward. Several alternative strategies are being developed, such as coupled hydrogeophysical inversion, or stochastic approaches using a prior falsification/validation method following a Popper-Bayes philosophy. In this talk, we will address some of these challenges and give some recent applications in the field of agro-geophysics. [less ▲]

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See detailEvaluation of the Effect of Micro-Topography of a Potato Field on ERT to Assess Soil Moisture Patterns in Sandy Soil
Manhaeghe, Thibault ULiege; Wagner, Florian; Dumont, Gaël ULiege et al

in Earthdoc (2018, September 09)

Electrical resistivity tomography is a method that provides a spatial-temporal characterization of the subsurface. In this project, the method is used to monitor a potato field, characterized by a ... [more ▼]

Electrical resistivity tomography is a method that provides a spatial-temporal characterization of the subsurface. In this project, the method is used to monitor a potato field, characterized by a microtopography composed of furrows and ridges. Nevertheless, changes of this micro-topography due to erosion during the growing season could lead to artefacts in the inverted resistivity distribution. To quantify this effect, we first used a hydraulic model with non-uniform infiltration patterns and converted the obtained soil moistures in bulk resistivities. We then conducted a forward modelling with a decrease of the ridge height in the mesh. Afterwards, we used the initial microtopography of the start of the growing season in the inversion and compared the retrieved resistivity distributions to the ones of the hydraulic model. We also compared different array configurations to assess which array is most suitable to retrieve the expected infiltration pattern. Gradient and Wenner configuration were performing best with a coefficient determination coefficient close to 0.9 and a RMS close to 1. The change of ridge height highly impacted the coefficient of determination once the decrease is above 6 cm. Nevertheless, pattern between furrows and ridges can still be retrieved qualitatively up until a decrease of 10 cm. [less ▲]

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See detailElectrical resistivity tomography: basic lecture (invited lecture)
Garré, Sarah ULiege

Conference (2018, August 28)

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See detailA new method for characterizing the complex electrical properties of root segments
Ehosioke, Solomon ULiege; Garré, Sarah ULiege; Kremer, Thomas ULiege et al

Conference (2018, July 09)

The application of geophysical methods to root investigation is increasing in recent years because of the limitations associated with the use of traditional methods (root excavation, monoliths ... [more ▼]

The application of geophysical methods to root investigation is increasing in recent years because of the limitations associated with the use of traditional methods (root excavation, monoliths, minirhizotron etc.). Point sampling is only partially satisfactory as a result of the spatial variability and dynamics of the roots zone. Geophysical methods address these limitations by offering high resolution and non-invasive approaches to root investigation due to their ability to infer properties and structures of the subsurface as well as the flow and transport processes occurring in the shallow subsurface, at various spatial scales. Recent studies (Weigand and Kemna 2017; Mary et al. 2017) have reported a low frequency polarization of root systems and have shown that SIP/EIT holds a promising future for root system characterization. Despite these significant improvements, there is still a knowledge gap regarding the electrical response of fine roots at the segment scale which is essential to enable us to account for the effect of roots in the estimation of soil moisture content of rooted soils or to exploit electromagnetic methods to characterize certain root system characteristics. We hereby propose a method for the characterization of electrical properties of single root segments of various plants resulting from an externally applied electrical field. A sample holder was designed and tested on ideal resistors and root segments, and was found to be suitable for assessing the electrical properties of root segments of 1-5 cm length and 2 mm diameter at a frequency range of 1Hz – 45 KHz. The system was then used to obtain complex electrical responses of the root segments of the target plants in the laboratory. This enabled us to study different root properties and their effects on the root electrical signals. Our results suggest that fine roots could be differentiated from soils because they show lower resistivity and polarizes more than soils. [less ▲]

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See detailSugar beet development under dynamic shade environments in temperate conditions
Artru, Sidonie ULiege; Lassois, Ludivine ULiege; Vancutsem, Francoise et al

in European Journal of Agronomy (2018), 97

In Wallonia (Belgium) almost half of the arable land undergoes a four-year crop rotation. Winter crops often follow spring crops within the rotation scheme. This is a challenging context to implement ... [more ▼]

In Wallonia (Belgium) almost half of the arable land undergoes a four-year crop rotation. Winter crops often follow spring crops within the rotation scheme. This is a challenging context to implement silvoarable agroforestry (AF) systems, in terms of species choice, plot design, and tree management, since the periods of crop resource capture clearly differ. AF is defined here as the deliberate introduction of trees in the cropped area. Combining spring crops with trees induces an important overlap of the growing period of both plants which has an impact on one of the primary resources for both plants: light. In this study, we monitored an important spring crop for the region, sugar beet (Beta vulgaris L.). We quantified the impact of the shade environment on sugar beet morphology, growth dynamic, productivity and quality. We used artificial shade to isolate the impact of shade from other possible interactions in agroforestry systems. The field experiment was conducted over two consecutive years (2015 and 2016) on the experimental farm of Gembloux Agro-Bio Tech, Belgium. We installed the shade structures so as to reproduce a North-South and East-West tree line orientation. The experiment simulated canopy shade of late-flushing hybrid walnut by overlapping military camouflage netting. In 2015, the North-South orientation induced two distinct shade conditions: periodic shade (PS) and continuous shade (CS). In 2016, the East-West orientation created two periodic shade treatments, one during the morning (PSam) and one in the afternoon (PSpm). In both experimental years, shading was imposed from mid-June until harvest, resulting in 132 days of shade in 2015, and 140 days in 2016 on a growing season of 192 (2015) and 188 (2016) days in total. Sugar beet under shade tended to produce longer petioles. In 2015, at the first sampling date, we observed a higher specific leaf area and single leaf area under the CS and PS treatment, while there were no differences in 2016. All the shade treatments significantly changed the dry matter partitioning between the sugar beets compartments. Under the shade treatments, the quantity of biomass allocated to the leaves was significantly reduced as compared to the proportion of biomass for the petioles. Likewise, quantity of root dry matter formed per gram of shoot dry matter was reduced under shade. Thus, at harvest, all the shade treatments significantly reduced the final root dry matter and sugar yield. Furthermore, sugar beet quality, and more specifically sugar extractability, was affected by shading but to a lesser extent than for the final root dry matter and sugar yield [less ▲]

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See detailImpact of crop residue management on crop production and soil chemistry after seven years of crop rotation in temperate climate, loamy soils
Hiel, Marie-Pierre ULiege; Barbieux, Sophie; Pierreux, Jérome ULiege et al

in PeerJ (2018), 6(e4836),

Society is increasingly demanding a more sustainable management of agro-ecosystems in a context of climate change and an ever growing global population. The fate of crop residues is one of the important ... [more ▼]

Society is increasingly demanding a more sustainable management of agro-ecosystems in a context of climate change and an ever growing global population. The fate of crop residues is one of the important management aspects under debate, since it represents an unneglectable quantity of organic matter which can be kept in or removed from the agro-ecosystem. The topic of residue management is not new, but the need for global conclusion on the impact of crop residue management on the agro-ecosystem linked to local pedo-climatic conditions has become apparent with an increasing amount of studies showing a diversity of conclusions. This study specifically focusses on temperate climate and loamy soil using a seven-year data set. Between 2008 and 2016, we compared four contrasting residue management strategies differing in the amount of crop residues returned to the soil (incorporation vs. exportation of residues) and in the type of tillage (reduced tillage (10 cm depth) vs. conventional tillage (ploughing at 25 cm depth)) in a field experiment. We assessed the impact of the crop residue management on crop production (three crops—winter wheat, faba bean and maize—cultivated over six cropping seasons), soil organic carbon content, nitrate (NO−3), phosphorus (P) and potassium (K) soil content and uptake by the crops. The main differences came primarily from the tillage practice and less from the restitution or removal of residues. All years and crops combined, conventional tillage resulted in a yield advantage of 3.4% as compared to reduced tillage, which can be partly explained by a lower germination rate observed under reduced tillage, especially during drier years. On average, only small differences were observed for total organic carbon (TOC) content of the soil, but reduced tillage resulted in a very clear stratification of TOC and also of P and K content as compared to conventional tillage. We observed no effect of residue management on the NO−3 content, since the effect of fertilization dominated the effect of residue management. To confirm the results and enhance early tendencies, we believe that the experiment should be followed up in the future to observe whether more consistent changes in the whole agro-ecosystem functioning are present on the long term when managing residues with contrasted strategies. [less ▲]

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