Compost application tends to increase soil fertility and is likely to modify soil hydrodynamic properties by acting on soil structural porosity. Two composts, a municipal solid waste compost (MSW) and a co-compost of green wastes and sewage sludge (SGW), have been applied every other year for 6 yr to cultivated plots located on a silt loam soil in the Parisian Basin, France. Four soil zones were defined in the topsoil after plowing: the plowpan located at the base of the plowed layer, compacted (Delta) or noncompacted (Gamma) zones located within the plowed layer, and interfurrows created by plowing and containing a large quantity of crop residues together with the recently-applied compost. To assess the effect of compost application on the near-saturated soil hydraulic conductivity, infiltration rates were measured using a tension disc infiltrometer at three water pressure potentials -0.6, -0.2, and -0.05 kPa in the various zones of the soil profile. Compost addition decreased K((sat)) in the interfurrows after plowing by almost one order of magnitude with average values of 5.6 x 10(-5) m.s(-1) in the MSW plot and 4.1 x 10(-5) m.s(-1) in the SGW plot, against 2.2 x 10(-4) m.s(-1) in the control plot. This effect had disappeared 6 mo after plowing when the average K((sat)) in the control plot had decreased to 1.9 x 10(-5) m.s(-1) while that in the compost-amended plots remained stable.

Ground-Penetrating Radar (GPR) was tested to monitor water infiltration in sand. Water was injected down an 81 cm long tubed hole, with a piezometer recording the depth of water and a tap valve used to adjust it to 15 cm ± 2 cm above the bottom of the tube. During the 20 minutes of infiltration a GPR system recorded a trace every second with its transmitter and receiver antennae at a fixed offset position on the surface. The signal, enhanced by differential correction, allows for tracing the evolution of top and bottom limits of the water bulb in space and time. Comparison with hydrodynamic model of the infiltration process and simulated radargrams prove that the GPR reflections trace the wetting front and the saturation bulb. A quantified estimation of the evolution of the top border of the wetting zone is provided.

To progress in the monitoring and understanding of soil water processes, geophysical methods can be helpful because they are noninvasive and as such do not disturb either the structure or the water dynamics of the soil. In this study we attempt to image water infiltration dynamics under a tension infiltrometer in a vertical two‐dimensional (2D) plane using electrical resistivity tomography (ERT). Two‐dimensional images of soil electrical resistivity at different times were obtained using a Wenner array with 32 electrodes and a 10‐cm spacing during the infiltration of a Cl− or Br− solution at 0.36 and 0.34 M, respectively. This procedure allowed monitoring the development of the infiltration bulb through time. Both unipotential and multipotential infiltrations were performed and used to derive soil hydraulic conductivity and sorptivity values. Anion concentrations in soil samples taken after infiltration were compared with resistivity values obtained with ERT measurements. The axisymetrical pattern of the multipotential infiltration exhibited large distortions, well detected and imaged by the ERT and consistent with the anion concentration data. In general, images derived from 2D inversions of ERT measurements underestimated the depth of the infiltration bulb. Axisymetrical inversion software would be helpful for the interpretation of ERT data taken below tension disc infiltrometers. The ERT on a small scale seems a helpful and promising tool for deriving in situ soil hydraulic parameters and for monitoring infiltration processes without the need for placing sensors into the soil.