References of "Garré, Sarah"
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See detailCrop residue management in arable cropping systems under a temperate climate. Part 2: Soil physical properties and crop production. A review
Hiel, Marie-Pierre ULg; Chelin, Marie ULg; Parvin, Nargish ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (in press)

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See detailAre crop models able to efficiently simulate crop growth under shade?
Artru, Sidonie ULg; Dumont, Benjamin ULg; Lassois, Ludivine ULg et al

in Gosme, Marie (Ed.) 3rd European Agroforestry conference 2016 - Book of abstracts (2016, May)

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See detailAssessment of a design to monitor the influence of crop residue management on the dynamics of soil water content with ERT
Chelin, Marie ULg; Hiel, Marie-Pierre ULg; Hermans, Thomas ULg et al

Poster (2016, April 21)

Choices related to crop residue management affect the soil structure. As a consequence, they may determinethe spatio-temporal dynamics of water content and eventually the crop yields. In order to better ... [more ▼]

Choices related to crop residue management affect the soil structure. As a consequence, they may determinethe spatio-temporal dynamics of water content and eventually the crop yields. In order to better understand the influence of these strategies on hydraulic processes occurring at the plot scale, we opted for the use electrical resistivity tomography (ERT). This approach presents the advantage to limit soil disturbance but is still faced to important challenges when applied in an agricultural field context. Especially changing soil-electrode contact has to be considered, as it can lead to bad quality data, especially for setups with small electrodes and small inter-electrode distance. The objective of this study was to test the efficiency of a high-resolution 3-D field measurement design to properly assess the dynamics of soil water content. ERT measurements were conducted in a Cutanic Siltic Luvisol in Gembloux, Belgium, on two plots of 2m^2 ploughed in Oct 2014 at a depth of 25 cm and sown with maize in April 2015. The plants were removed on one of the plots in order to obtain a bare soil reference. A grid of 98 surface stainless steel electrodes was layed-out on each plot and four sticks supporting each eight stainless steel electrodes were vertically inserted into the soil up to 1.20 m to get more detailed information in depth. The experiments were performed between Jul and Oct 2015, in order to get measurements both in dry and wet periods. For surface and borehole monitoring, a dipole-dipole array configuration including in-line and cross-line measurements was adopted. Normal and reciprocal measurements were performed systematically to assess the data quality: only the datasets with a mean reciprocal error lower than 3% were considered for the data inversion. This contribution will show the first inverted results showing the complexity of experimental design and data analysis for high-resolution, timelapse ERT in field conditions. Based on these results, we will draw conclusions about a minimal data set to be obtained in our upcoming field experiments. [less ▲]

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See detailTime lapse imaging of water content with geoelectrical methods: on the interest of working with absolute water content data
Dumont, Gaël ULg; Pilawski, Tamara ULg; Robert, Tanguy et al

Poster (2016, April 21)

The electrical resistivity tomography is a suitable method to estimate the water content of a waste material and detect changes in water content. Various ERT profiles, both static data and time-lapse ... [more ▼]

The electrical resistivity tomography is a suitable method to estimate the water content of a waste material and detect changes in water content. Various ERT profiles, both static data and time-lapse, where acquired on a landfill during the Minerve project. In the literature, the relative change of resistivity ( Delta rho/rho ) is generally computed. For saline or heat tracer tests in the saturated zone, the Delta rho/rho can be easily translated into pore water conductivity or underground temperature changes (provided that the initial salinity or temperature condition is homogeneous over the ERT panel extension). For water content changes in the vadose zone resulting of an infiltration event or injection experiment, many authors also work with the Delta rho/rho or relative changes of water content Delta theta /theta (linked to the change of resistivity through one single parameter: the Archie’s law exponent “m”). This parameter is not influenced by the underground temperature and pore fluid conductivity ( rho_w) condition but is influenced by the initial water content distribution. Therefore, you never know if the loss of / signal is representative of the limit of the infiltration front or more humid initial condition. Another approach for the understanding of the infiltration process is the assessment of the absolute change of water content ( Delta theta ). This requires the direct computation of the water content of the waste from the resistivity data. For that purpose, we used petrophysical laws calibrated with laboratory experiments and our knowledge of the in situ temperature and pore fluid conductivity parameters. Then, we investigated water content changes in the waste material after a rainfall event ( Delta theta = Delta theta /theta * theta ). This new observation is really representatives of the quantity of water infiltrated in the waste material. However, the uncertainty in the pore fluid conductivity value may influence the computed water changes ( Delta theta =k*m*(rho_w)^1/2 ; where “m” is the Archie’s law exponent). Using these two complementary approaches, we analyzed the effect a major rainfall (20-30 mm in 2 hours) that occurred on the test site, characterized by a vegetalized and relatively dry zone and a devegatelized and humid zone. We intended to prove that most of the information contained in the Delta theta /theta distribution is the initial water content distribution in the ground.Water addition in dry zones resulting in large relative changes. The computation of the Delta theta is necessary to demonstrate preferential infiltration through the capping in a restricted zone of the vegetalized area. [less ▲]

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See detailImpact of tillage practices on soil moisture dynamics in a temperate climate: potential of 3-D electrical resistivity tomography (ERT)
Chelin, Marie ULg; Hiel, Marie-Pierre ULg; Blanchy, Guillaume et al

Poster (2016, April 12)

Adapted agricultural soil management practices can enhance soil health by providing improved aggregate stability and soil structural quality. Hence water infiltration may be improved and plant water ... [more ▼]

Adapted agricultural soil management practices can enhance soil health by providing improved aggregate stability and soil structural quality. Hence water infiltration may be improved and plant water availability increased. In this study, we aim at quantifying the effect of tillage practices on the water dynamics in a loamy soil under temperate climate (Gembloux, Belgium). Therefore, we evaluated the ability of electrical resistivity tomography to estimate the water content at the field scale and under complex field conditions: varying pore water conductivity, rainfall, crop water uptake, root growth, varying temperature and changing soil structure due to tillage practices. During the summer of 2015, we studied four different treatments: conventional spring and winter tillage, strip tillage and a bare soil. We used ERT to estimate the spatio-temporal distribution of soil moisture. In each of the plots, 2 time-domain reflectometry (TDR) probes and 2 suction cups were installed. A calibration trench was constructed with 4 electrodes, 1 TDR probe and 1 temperature sensor at 4 different depths. We quantified changes of porosity over the growing season using X-ray tomography. Combining these data, we will investigate and quantify the effect of simultaneously changing pore water conductivity, soil porosity, soil temperature and soil moisture on the effectiveness of time-lapse ER measurements as a proxy for soil moisture changes under different tillage practices. [less ▲]

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See detailSoil apparent conductivity measurements for planning and analysis of agricultural experiments: A case study from Western-Thailand
Rudolph, Sebastian; Wongleecharoen, Chalemchart; Lark, Murray et al

in Geoderma (2016), 267

In experimental trials, the success or failure of agricultural improvements is commonly evaluated on the agronomic response of crops, using proper experimental designs with sufficient statistical power ... [more ▼]

In experimental trials, the success or failure of agricultural improvements is commonly evaluated on the agronomic response of crops, using proper experimental designs with sufficient statistical power. Since fine-scale variability of the experimental site can reduce statistical power, efficiency gains in the experimental design can be achieved if this variation is known and used to design blocking, or some proxy variable is used as a covariate. Near-surface geophysical techniques such as electromagnetic induction (EMI), which describes subsurface properties non-invasively by measuring soil apparent conductivity (ECa), may be one source of this information. The motivation of our study was to investigate the effectiveness of EMI-derived ECa measurements for planning and analysis of agricultural experiments. ECa and plant height measurements (the response variable) were taken from an agroforestry experiment in Western Thailand, and their variability was quantified to simulate multiple realizations of ECa and the residuals of the response variable from treatment means. These were combined to produce simulated data from different experimental designs and treatment effects. The simulated data were then used to evaluate the statistical power by detecting three orthogonal contrasts among the treatments in the original experiment. We considered three experimental designs, a simple random design (SR), a complete randomized block design (CRB), and a complete randomized block design with spatially adjusted blocks on plot means of ECa (CRBECa). Using analysis of variance (ANOVA), the smallest effect sizes could be detected with the CRBECa design, which indicates that ECa measurements could be used in the planning phase of an experiment to achieve efficiencies by improved blocking. In contrast, analysis of covariance (ANCOVA) demonstrated that substantial power improvements could be gained when ECa was considered as a covariate in the analysis. We therefore recommend that ECa measurements should be used to characterize subsurface variability of experimental sites and to support the statistical analysis of agricultural experiments. [less ▲]

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See detailInfluence of plant roots on electrical resistivity measurements of cultivated soil columns
Maloteau, Sophie ULg; Blanchy, Guillaume ULg; Javaux, Mathieu et al

Poster (2016, April)

The goals of this experiment are to quantify the effect of plant roots on electrical resistivity of the soil subsurface and to map a plant roots system in space and time with ERT technique in a soil ... [more ▼]

The goals of this experiment are to quantify the effect of plant roots on electrical resistivity of the soil subsurface and to map a plant roots system in space and time with ERT technique in a soil column. For this research, it is assumed that roots system affect the electrical properties of the rhizosphere. Indeed the root activity (by transporting ions, releasing exudates, changing the soil structure,…) will modify the rhizosphere electrical conductivity (Lobet G. et al, 2013). This experiment is included in a bigger research project about the influence of roots system on geophysics measurements. Measurements are made on cylinders of 45 cm high and a diameter of 20 cm, filled with saturated loam on which seeds of Brachypodium distachyon (L.) Beauv. are sowed. Columns are equipped with electrodes, TDR probes and temperature sensors. Experiments are conducted at Gembloux Agro-Bio Tech, in a growing chamber with controlled conditions: temperature of the air is fixed to 20°C, photoperiod is equal to 14 hours, photosynthetically active radiation is equal to 200 µmol m-2s-1, and air relative humidity is fixed to 80 %. Columns are fully saturated the first day of the measurements duration then no more irrigation is done till the end of the experiment. [less ▲]

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See detailTowards sustainable food systems: the concept of agroecology and how it questions current research practices. A review
Hatt, Séverin ULg; Artru, Sidonie ULg; Brédart, David ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016), 20(Special issue 1), 215-224

Introduction. Multiple environmental and socio-economic indicators show that our current agriculture and the organization of the food system need to be revised. Agroecology has been proposed as a ... [more ▼]

Introduction. Multiple environmental and socio-economic indicators show that our current agriculture and the organization of the food system need to be revised. Agroecology has been proposed as a promising concept for achieving greater sustainability. This paper offers an overview and discussion of the concept based on existing literature and case studies, and explores the way it questions our current research approaches and education paradigms. Literature. In order to improve the sustainability of agriculture, the use of external and chemical inputs needs to be minimized. Agroecological farming practices seek to optimize ecological processes, thus minimizing the need for external inputs by providing an array of ecosystem services. Implementing such practices challenges the current structure of the food system, which has been criticized for its lack of social relevance and economic viability. An agroecological approach includes all stakeholders, from field to fork, in the discussion, design and development of future food systems. This inclusion of various disciplines and stakeholders raises issues about scientists and their research practices, as well as about the education of the next generation of scientists. Conclusions. Agroecology is based on the concept that agricultural practices and food systems cannot be dissociated because they belong to the same natural and socio-economic context. Clearly, agroecology is not a silver-bullet, but its principles can serve as avenues for rethinking the current approaches towards achieving greater sustainability. Adapting research approaches in line with indicators that promote inter- and transdisciplinary research is essential if progress is to be made. [less ▲]

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See detailCaractérisation des propriétés hydrauliques de sols caillouteux
Pichault, Mathieu; Garré, Sarah ULg

Conference (2015, November 24)

La détermination des propriétés hydrauliques du sol est une préoccupation majeure dans différents domaines d’études. Bien que les sols caillouteux soient répandus dans le monde entier, la plupart des ... [more ▼]

La détermination des propriétés hydrauliques du sol est une préoccupation majeure dans différents domaines d’études. Bien que les sols caillouteux soient répandus dans le monde entier, la plupart des études ne caractérisent que la fraction fine des sols, si bien que la littérature décrivant l’impact des cailloux sur les propriétés hydrauliques du sol est encore rare. Certains modèles ayant pour but de caractériser ces propriétés hydrauliques reposent sur la même hypothèse simplificatrice, qui stipule que le seul effet des cailloux est de diminuer le volume disponible pour l’écoulement de l’eau. L’objectif de cette étude est de vérifier cette hypothèse et, le cas échéant, d’identifier les facteurs déterminant ou non son respect. L’effet des cailloux sur la conductivité hydraulique à saturation effective du sol a été testé au moyen d’expériences de laboratoire et d’expériences numériques, impliquant différentes quantités et types de fragments grossiers. Nos résultats montrent que plusieurs facteurs supplémentaires, non considérés par ces modèles, peuvent affecter significativement la conductivité hydraulique à saturation. D’une part, la forme et la taille des inclusions altèrent de manière substantielle la conductivité hydraulique. D’autre part, la présence de cailloux peut contrer -voire dominer- les effets liés à la réduction du volume disponible pour l’écoulement en conditions saturantes. Nous attribuons cela à la création de macropores à l’interface entre la terre fine et les cailloux. [less ▲]

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See detailERT monitoring of water infiltration process through a landfill cover layer
Dumont, Gaël ULg; Pilawski, Tamara ULg; Robert, Tanguy et al

in Berichte der Geologischen Bundesanstalt, 112 (2015, November)

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See detailLes sols, richesses cachées de la planète
Garré, Sarah ULg; Carnol, Monique ULg; Cornelis, Jean-Thomas ULg

Speech/Talk (2015)

Toute forme de vie sur terre doit beaucoup aux sols. Aussi discrets que dynamiques, vitaux que complexes, les sols sont des réacteurs bio-physico-chimiques, situés à l’interface entre les roches, la ... [more ▼]

Toute forme de vie sur terre doit beaucoup aux sols. Aussi discrets que dynamiques, vitaux que complexes, les sols sont des réacteurs bio-physico-chimiques, situés à l’interface entre les roches, la végétation, l’air et l’eau. L’étude de cette ressource non renouvelable, soumise à des pressions croissantes, requiert une approche interdisciplinaire, indispensable pour une gestion raisonnée et durable des écosystèmes. Comment sont définis les sols, comment les étudions-nous, comment aborder leur diversité et leurs fonctionnalités ? Quels secrets ont-ils à nous livrer ? La leçon inaugurale abordera la formation des sols, leur diversité ainsi que leurs fonctions écologiques. La variété des organismes au sein des sols et la notion de qualité des sols seront évoquées à travers la triangulation biodiversité – fonctions – services écosystémiques. Des techniques innovantes, permettant d’étudier cette interface extrêmement complexe et diversifiée, seront présentées et le fonctionnement ainsi que l’intérêt des sols seront illustrés par des exemples concrets issus de recherches récentes. [less ▲]

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See detailGeophysics for the quantification of water fluxes in the soil-plant system
Garré, Sarah ULg; Binley, Andrew

Conference (2015, September 17)

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See detailAgroecology: Unity into diversity
Hatt, Séverin ULg; Artru, Sidonie ULg; Boeraeve, Fanny ULg et al

Poster (2015, May 21)

What does agroecology suggest ? Next to the theoretical agroecological principles, we present illustrative examples from farming practices, through the food system, up to the way of carrying agricultural ... [more ▼]

What does agroecology suggest ? Next to the theoretical agroecological principles, we present illustrative examples from farming practices, through the food system, up to the way of carrying agricultural research and education. [less ▲]

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See detailEvaluation of soil structural changes through macroscopic and microscopic measurement
Parvin, Nargish ULg; Degré, Aurore ULg; Chelin, Marie ULg et al

Poster (2015, April 16)

The heterogeneity of soil structure and pore size distribution are highly influenced by external factors like tillage systems and other agricultural management practices. However, changes in soil ... [more ▼]

The heterogeneity of soil structure and pore size distribution are highly influenced by external factors like tillage systems and other agricultural management practices. However, changes in soil hydrodynamic behavior are not fully understood and are still under research. Also, researchers have explained the impact of tillage practices on soil hydraulic properties related to pore size distribution, connectivity and orientation are involved but the characterization of these modifications and consequences remains a challenge. Furthermore, the relation between macroscopic measurements and microscopic investigation of the soil structure remains scarce. Recently, X-ray tomography (X- μCT) has been used in order to characterize changes in soil pore size distribution in various contexts and the method is able to link microtomography information to hydrodynamic measurement. In our study, X-μCT has been used in order to characterize changes in soil pore system. Since, tomography does not count most of the micropores, Richards’ pressure plate and evaporation method was also combined to get complete range of pore size distribution. We found good match between evaporation data with X-μCT at the macropore scale and evaporation data with pressure plate method at micropore scale. X-μCT data refines retention and hydraulic curves near saturation where Richards’ data alone can lead to numerous sets of fitted parameters. On the otherhand, evaporation data (Hyprop apparatus ©) provide comparable datasets with X-μCT. Combining micro and macroscopic measurements allows us to validate X-μCT information, which is otherwise not so obvious. [less ▲]

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See detailExperimental design to monitor the influence of crop residue management on the dynamics of soil water content
Chelin, Marie ULg; Parvin, Nargish ULg; Hiel, Marie-Pierre ULg et al

Poster (2015, April 15)

Choices related to crop residue management affecting soil structure determine spatio-temporal dynamics of water content and eventually crop yields. In this contribution, we discuss the experimental design ... [more ▼]

Choices related to crop residue management affecting soil structure determine spatio-temporal dynamics of water content and eventually crop yields. In this contribution, we discuss the experimental design we adopted to study the influence of three different agricultural management strategies (tillage and residue management) on the soil water dynamics under maize in a Cutanic Siltic Luvisol in Gembloux, Belgium. In order to limit soil disturbance, we opted for the use electrical resistivity tomography (ERT) and we use the bulk electrical conductivity as a proxy for soil moisture content. ERT is collected every week on a surface of two square meters corresponding to three rows of seven maize plants through surface stainless steel electrodes. Four additional sticks with stainless steel electrodes will be vertically inserted into the soil up to 1.20 m to get more detailed information near to the central maize row. In each of the monitoring plots, two time-domain reflectometry (TDR) probes will be installed for data validation. In order to calibrate the relationship between electrical resistivity and soil water content under highly variable field conditions (changes in soil structure, variable weather conditions, plant growth, fertilization), a trench will be dug, in which a set of four electrodes, one TDR probe and one temperature sensor will be placed at four different depths. In addition, two suction cups will be installed in each of the plots to quantify changes in ion composition and electrical conductivity of the soil solution at two different depths. Within the framework of the multidisciplinary research platform AgricultureIsLife, regular assessment of pore structure and crop developement will be conducted using X-ray images. Combining this wide range of data, we will be able to investigate and quantify the effect of simultaneously changing pore water conductivity, soil porosity, soil temperature and soil moisture on the effectiveness of time-lapse ER measurements as a proxy for soil moisture changes. [less ▲]

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See detailCombining δ13C measurements and ERT imaging: improving our understanding of competition at the crop-soil-hedge interface
Hussain, Khalid; Wongleecharoen, Chalemchart; Hilger, Thomas et al

in Plant and Soil (2015)

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See detailSoil porosity in agricultural context: A review of measurement techniques at various scales
Garré, Sarah ULg; Chelin, Marie ULg; Luong, Jeanne ULg et al

Poster (2015, April 13)

Soil compaction was identified by European Commission as one of the eight main threats for agricultural soils. In order to address this issue, measurements of soil porosity are critical. However, there ... [more ▼]

Soil compaction was identified by European Commission as one of the eight main threats for agricultural soils. In order to address this issue, measurements of soil porosity are critical. However, there are as many techniques to measure as there are definitions of porosity. A single method is not sufficient to obtain a complete image of the soil porosity at various scales and encompassing different levels of complexity. Each existing method is characterized by a unique combination of a specific level of complexity, resolution and scale of measurement. In this review, we started by defining the basic terms linked to soil porosity in an agricultural context. Then we give an overview of relevant measurement techniques, from classical methods to recent advances. We present their advantages and disadvantages, the scales of measurement, the resolution, the expected accuracy and the susceptibility to errors. This work aims at guiding the choice for the best (combination of) technique(s) to answer questions related to agricultural soil porosity, categorizing techniques according to the parameters they focus on: from total porosity over pore size distribution, structure and connectivity up to the quantification of spatio-temporal dynamics. [less ▲]

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