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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; Marchant, B. et al

E-print/Working paper (2013)

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See detailParameterizing a Dynamic Architectural Model of the Root System of Spring Barley from Minirhizotron Data
Garré, Sarah ULg; Pagès, Loïc; Laloy, Eric et al

in Vadose Zone Journal (2012)

The development of models describing water and nutrient fluxes to and through 3-D spatially resolved root structures in soils brings along the need to predict or describe the root architecture and root ... [more ▼]

The development of models describing water and nutrient fluxes to and through 3-D spatially resolved root structures in soils brings along the need to predict or describe the root architecture and root growth in detail. However, detailed data to calibrate and validate such architecture and growth models is typically not available. Here, we investigate the sensitivity of the root architecture model RootTyp (Pagès et al., 2004) to changes in its model parameters and reconstructed the root system architecture of barley growing in an undisturbed lysimeter using minirhizotron images at four different depths. Root arrival curves from a series of minirhizotron images were used to parameterize RootTyp using a range of realistic architectures. We adjusted a simple architecture to the data, which contained only long primary roots starting from the seed. This simple model unfortunately could not reproduce the observed increase of root density with depth. The model was subsequently improved by allowing root branching and elongation to be horizon-dependent and by making reiteration of root tips possible. Reiteration is an alternative form of branching, where secondary roots can become as long and thick as primary roots. Our results show that minirhizotron data do not contain enough information to warrant identification of the parameters governing these processes, as the additional parameters act similarly on data characteristics as the initial ones. Therefore, different experimental techniques should be combined to constrain the model parameters better in the future. [less ▲]

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See detailParameterizing the root system development of summer barley using minirhizotron data
Garré, Sarah ULg; Pagès, Loïc; Javaux, Mathieu et al

Poster (2011, April)

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See detailThree-Dimensional Electrical Resistivity Tomography to Monitor Root Zone Water Dynamics
Garré, Sarah ULg; Javaux, Mathieu; Vanderborght, Jan et al

in Vadose Zone Journal (2011), 10(1), 412-424

Knowledge of soil moisture dynamics and its spatial variability is essential to improve our understanding of root water uptake and soil moisture redistribution at the local scale and the field scale. We ... [more ▼]

Knowledge of soil moisture dynamics and its spatial variability is essential to improve our understanding of root water uptake and soil moisture redistribution at the local scale and the field scale. We investigated the potential and limitations of electrical resistivity tomography (ERT) to measure three-dimensional soil moisture changes and variability in a large, undisturbed, cropped soil column and examined the interactions between soil and root system. Our analysis sustained the value of ERT as a tool to monitor and quantify water contents and water content changes in the soil, as long as the root biomass does not influence the observed resistivity. This is shown using a global water mass balance and a local validation using time domain reflectometry (TDR) probes. The observed soil moisture variability was rather high compared to values reported in the literature for bare soil. The measured water depletion rate, being the result of combined effects of root water uptake and soil water redistribution, was compared with the evaporative demand and root length densities. We observed a gradual downward movement of the maximum water depletion rate combined with periods of redistribution when there was less transpiration. Finally, the maximum root length density was observed at −70 cm depth, pointing out that root architecture can strongly depend on soil characteristics and states. [less ▲]

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See detailThe role of soil-root interface for transport processes in soils
Vanderborght, Jan; Schröder, Nathalie; Garré, Sarah ULg et al

in Abstracts AGU (2011)

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See detailThe dynamic interplay between roots and soil moisture
Garré, Sarah ULg; Vanderborght, Jan; Javaux, Mathieu et al

in Geophysical Research Abstracts (2010, May)

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See detailComparison of Heterogeneous Transport Processes Observed with Electrical Resistivity Tomography in Two Soils
Garré, Sarah ULg; Koestel, Johannes; Günther, Thomas et al

in Vadose zone journal (2010), 9(2), 336-349

Preferential flow in soils can manifest itself in several ways. To illustrate this, we analyzed solute transport during a step tracer experiment in two soils expected to differ in their governing ... [more ▼]

Preferential flow in soils can manifest itself in several ways. To illustrate this, we analyzed solute transport during a step tracer experiment in two soils expected to differ in their governing transport processes: a loamy sand and a silty soil. By combining electrical resistivity tomography (ERT), time domain reflectometry, and effluent measurements, we observed different preferential flow phenomena. The transport process was characterized using voxel- and column-scale effective convective–dispersive equation (CDE) parameters, local velocities, and leaching surfaces. At the column scale, transport in the loamy sand was dominated by a homogenous convective–dispersive transport behavior, but at the scale of the voxel, preferential transport was observed. Transport in the silty soil was considerably more heterogeneous. Preferential flow was identified using ERT, voxel- and column-scale effective CDE parameters, local velocities, and leaching surfaces. In these soils, a clear influence of soil layering on solute transport was observed. [less ▲]

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See detailA generalized frequency domain reflectometry forward and inverse modeling technique for soil electrical properties determination
Minet, Julien ULg; Lambot, Sébastien; Delaide, Géraldine et al

in Vadose Zone Journal (2010), 9(4)

We have developed a generalized frequency domain reflectometry (FDR) technique for soil characterization that is based on an electromagnetic model decoupling the cable and probe head from the ground using ... [more ▼]

We have developed a generalized frequency domain reflectometry (FDR) technique for soil characterization that is based on an electromagnetic model decoupling the cable and probe head from the ground using frequency-dependent reflection and transmission transfer functions. The FDR model represents an exact solution of Maxwell’s equations for wave propagation in one-dimensional multilayered media. The benefit of the decoupling is that the FDR probe can be fully described by its characteristic transfer functions, which are determined using only a few measurements. The soil properties are retrieved after removing the probe effects from the raw FDR data by iteratively inverting a global reflection coefficient. The proposed method was validated under laboratory conditions for measurements in water with different salt concentrations and sand with different water contents. For the salt water, inversions of the data led to dielectric permittivity and electrical conductivity values very close to the expected theoretical or measured values. In the frequency range for which the probe is efficient, a good agreement was obtained between measured, inverted and theoretically predicted signals. For the sand, results were consistent with the different water contents and also in close agreement with traditional time domain reflectometry measurements. The proposed method offers great promise for accurate soil electrical characterization because it inherently permits maximization of the information that can be retrieved from the FDR data and shows a high practicability. [less ▲]

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See detailDetecting preferential flow and transport in soils using electrical resistivity tomography
Vanderborght, Jan; Oberdoerster, Christoph; Garré, Sarah ULg et al

Conference (2009)

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See detailElectrical resistivyt tomography as tool to image preferential flow pathways in soils
Kasteel, Roy; Garré, Sarah ULg; Koestel, Johannes et al

Conference (2009)

Detailed reference viewed: 11 (2 ULg)