In soil physics, water retention and hydraulic conductivity are key parameters for predicting wat... more In soil physics, water retention and hydraulic conductivity are key parameters for predicting water fluxes in soils. Determination of these hydrodynamic characteristics in the lab, particularly unsaturated hydraulic conductivity, is most often complicated, time consuming and error-prone. These difficulties often prohibit the examination of numerous soil samples for determining these parameters as would be necessary to get a good estimation of the field variability. In this case, an indirect and easy to measure variable, closely linked to water retention or hydraulic conductivity, would be helpful in the assessment of these parameters. Electrical conductivity (EC) is a good candidate for such a variable because, in a porous medium, its magnitude is largely determined by the number of water filled pores and their connectivity. Relationships between water content (or saturation) and EC have been established both from empirical or theoretical point of view for some time. However, relationships between EC and unsaturated hydraulic conductivity are much more scarce, as are experimental data. We present relationships between EC and water content or water potential for three soil types: a clay loam, a sandy loam and a sand. We also present experimental relationship between EC and unsaturated hydraulic conductivity for the sandy loam. The soil were cored in the field with PVC tubes 9.5 cm inner diameter × 3 cm height. Water retention was measured using sand boxes and pressure plates apparatus. Hydraulic conductivity was calculated from the Wind evaporation method and from steady state measurements for low suctions. For each suction, the EC of the bulk was calculated from complex impedance measurements at various frequencies using two circular stainless steal electrodes located above and at the bottom of the soil core. Mercury porosimetry measurements were also performed after the experiments. Water saturation reasonably follows a power-law relationship with relative EC (EC/ECsat). Exponents of the power law being around 3--3.5 for the clay loam, 1.1--1.7 for the sandy loam and 8--12 for the sand (for matric potentials between 0 and -80 cm in the latter case). Variation of the relative EC with the log of water potential shows a S-shape, with an almost linear part in a range potential depending on the soil type. The hydraulic conductivity is a decreasing function of the relative EC, the saturated hydraulic conductivity being in agreement with the model of Katz and Thomson.
In soil physics, water retention and hydraulic conductivity are key parameters for predicting wat... more In soil physics, water retention and hydraulic conductivity are key parameters for predicting water fluxes in soils. Determination of these hydrodynamic characteristics in the lab, particularly unsaturated hydraulic conductivity, is most often complicated, time consuming and error-prone. These difficulties often prohibit the examination of numerous soil samples for determining these parameters as would be necessary to get a good estimation of the field variability. In this case, an indirect and easy to measure variable, closely linked to water retention or hydraulic conductivity, would be helpful in the assessment of these parameters. Electrical conductivity (EC) is a good candidate for such a variable because, in a porous medium, its magnitude is largely determined by the number of water filled pores and their connectivity. Relationships between water content (or saturation) and EC have been established both from empirical or theoretical point of view for some time. However, relati...
An evaluation of the effects of soil structural heterogeneity on maize (Zea maysL.) root system a... more An evaluation of the effects of soil structural heterogeneity on maize (Zea maysL.) root system architecture was carried out on plants grown in boxes containing fine soil and clods. The clods were prepared at two levels of moisture (0.17 and 0.20 g/g) and bulk density (ranges 1.45–1.61 g/ml and 1.63–1.79 g/ml). Soil moisture directly affected the probability of clod penetration by maize roots. Primary roots inside the clods manifested morpholo-gical deformations in the form of bends. We observed a significant increase of bends per root length at lower soil moisture (P = 0.02). Root diameter and branching density increased, and lateral root length decreased considerably inside the clods. However, once emerging out of the clods and into free soil, values of all three characteristics re-mained low. While changes in root diameter were caused mainly by clod moisture (P < 0.05), length of lateral roots was related to bulk density (P < 0.01). Branching density was modified exclusivel...
An experimental investigation was undertaken to study the ability of Spectral Induced Polarizatio... more An experimental investigation was undertaken to study the ability of Spectral Induced Polarization (SIP) method to monitor the water infiltration in a silty clay loam soil. It was based on the coupled acquisition of tensiometer data and Spectral Induced Polarization (SIP) spectra (1.46 Hz to 12 kHz) during the infiltration event created by an artificial constant rainfall rate of about 15 mm/hr. This approach that was applied both in the field and in a soil column confirms the existence of a significant phase drop in the high-frequency domain (typically greater than 1 kHz) during the first infiltration cycles. The interpretation of tensiometer data and SIP data show that this phase drop is correlated with the water filling of pores in the (30-85) m diameter range. This study suggests strongly that the SIP method would be able to give valuable information about the water filling of bigger pores (i.e., structural pores or fast draining pores). This original result should be validated i...
A 2D physically based framework is proposed to analyze the effect of a non-uniform water supply a... more A 2D physically based framework is proposed to analyze the effect of a non-uniform water supply at the soil surface generated by rainfall interception and stemflow on soil-root water transport in the case of heterogeneous distribution of the roots in the soil profile. To model soil-root water transport, the root water potential of two plants placed in two adjacent rows
... eg, Gex, 1980), CO2 seques-tration (Moore et al., 2004; Moore and Glaser, 2004), and ... We c... more ... eg, Gex, 1980), CO2 seques-tration (Moore et al., 2004; Moore and Glaser, 2004), and ... We consider here the fundamental mechanisms of natural polarization in the ground from a ... fundamental properties of electrical properties in the quasi-static limit of the Maxwell equations. ...
In soil physics, water retention and hydraulic conductivity are key parameters for predicting wat... more In soil physics, water retention and hydraulic conductivity are key parameters for predicting water fluxes in soils. Determination of these hydrodynamic characteristics in the lab, particularly unsaturated hydraulic conductivity, is most often complicated, time consuming and error-prone. These difficulties often prohibit the examination of numerous soil samples for determining these parameters as would be necessary to get a good estimation of the field variability. In this case, an indirect and easy to measure variable, closely linked to water retention or hydraulic conductivity, would be helpful in the assessment of these parameters. Electrical conductivity (EC) is a good candidate for such a variable because, in a porous medium, its magnitude is largely determined by the number of water filled pores and their connectivity. Relationships between water content (or saturation) and EC have been established both from empirical or theoretical point of view for some time. However, relationships between EC and unsaturated hydraulic conductivity are much more scarce, as are experimental data. We present relationships between EC and water content or water potential for three soil types: a clay loam, a sandy loam and a sand. We also present experimental relationship between EC and unsaturated hydraulic conductivity for the sandy loam. The soil were cored in the field with PVC tubes 9.5 cm inner diameter × 3 cm height. Water retention was measured using sand boxes and pressure plates apparatus. Hydraulic conductivity was calculated from the Wind evaporation method and from steady state measurements for low suctions. For each suction, the EC of the bulk was calculated from complex impedance measurements at various frequencies using two circular stainless steal electrodes located above and at the bottom of the soil core. Mercury porosimetry measurements were also performed after the experiments. Water saturation reasonably follows a power-law relationship with relative EC (EC/ECsat). Exponents of the power law being around 3--3.5 for the clay loam, 1.1--1.7 for the sandy loam and 8--12 for the sand (for matric potentials between 0 and -80 cm in the latter case). Variation of the relative EC with the log of water potential shows a S-shape, with an almost linear part in a range potential depending on the soil type. The hydraulic conductivity is a decreasing function of the relative EC, the saturated hydraulic conductivity being in agreement with the model of Katz and Thomson.
In soil physics, water retention and hydraulic conductivity are key parameters for predicting wat... more In soil physics, water retention and hydraulic conductivity are key parameters for predicting water fluxes in soils. Determination of these hydrodynamic characteristics in the lab, particularly unsaturated hydraulic conductivity, is most often complicated, time consuming and error-prone. These difficulties often prohibit the examination of numerous soil samples for determining these parameters as would be necessary to get a good estimation of the field variability. In this case, an indirect and easy to measure variable, closely linked to water retention or hydraulic conductivity, would be helpful in the assessment of these parameters. Electrical conductivity (EC) is a good candidate for such a variable because, in a porous medium, its magnitude is largely determined by the number of water filled pores and their connectivity. Relationships between water content (or saturation) and EC have been established both from empirical or theoretical point of view for some time. However, relati...
An evaluation of the effects of soil structural heterogeneity on maize (Zea maysL.) root system a... more An evaluation of the effects of soil structural heterogeneity on maize (Zea maysL.) root system architecture was carried out on plants grown in boxes containing fine soil and clods. The clods were prepared at two levels of moisture (0.17 and 0.20 g/g) and bulk density (ranges 1.45–1.61 g/ml and 1.63–1.79 g/ml). Soil moisture directly affected the probability of clod penetration by maize roots. Primary roots inside the clods manifested morpholo-gical deformations in the form of bends. We observed a significant increase of bends per root length at lower soil moisture (P = 0.02). Root diameter and branching density increased, and lateral root length decreased considerably inside the clods. However, once emerging out of the clods and into free soil, values of all three characteristics re-mained low. While changes in root diameter were caused mainly by clod moisture (P < 0.05), length of lateral roots was related to bulk density (P < 0.01). Branching density was modified exclusivel...
An experimental investigation was undertaken to study the ability of Spectral Induced Polarizatio... more An experimental investigation was undertaken to study the ability of Spectral Induced Polarization (SIP) method to monitor the water infiltration in a silty clay loam soil. It was based on the coupled acquisition of tensiometer data and Spectral Induced Polarization (SIP) spectra (1.46 Hz to 12 kHz) during the infiltration event created by an artificial constant rainfall rate of about 15 mm/hr. This approach that was applied both in the field and in a soil column confirms the existence of a significant phase drop in the high-frequency domain (typically greater than 1 kHz) during the first infiltration cycles. The interpretation of tensiometer data and SIP data show that this phase drop is correlated with the water filling of pores in the (30-85) m diameter range. This study suggests strongly that the SIP method would be able to give valuable information about the water filling of bigger pores (i.e., structural pores or fast draining pores). This original result should be validated i...
A 2D physically based framework is proposed to analyze the effect of a non-uniform water supply a... more A 2D physically based framework is proposed to analyze the effect of a non-uniform water supply at the soil surface generated by rainfall interception and stemflow on soil-root water transport in the case of heterogeneous distribution of the roots in the soil profile. To model soil-root water transport, the root water potential of two plants placed in two adjacent rows
... eg, Gex, 1980), CO2 seques-tration (Moore et al., 2004; Moore and Glaser, 2004), and ... We c... more ... eg, Gex, 1980), CO2 seques-tration (Moore et al., 2004; Moore and Glaser, 2004), and ... We consider here the fundamental mechanisms of natural polarization in the ground from a ... fundamental properties of electrical properties in the quasi-static limit of the Maxwell equations. ...
Uploads