Ground Conductivity Meter Research Articles

Temporal and Spatial Assessment of Soil Salinity Post-Flood Irrigation: A Guide to Optimal Cotton Sowing Timing

Flood irrigation is often applied in the arid regions of Northwest China to facilitate the leaching of salts accumulated in the soil during cotton growth in the previous season. This will, in turn, affect the temporal and spatial patterns of soil salinity, and thus cotton germination. To reveal the salinity of the two soil layers (0–20 cm and 20–60 cm), so as to determine the optimal cotton sowing timing, an electronic ground conductivity meter (EM38-MK2) was employed to measure the soil apparent electrical-conductivity (ECa) on different days: 4 days prior to flood irrigation, and, respectively, 6, 10, 15, 20, and 45 days after flood irrigation. Moreover, geostatistical analysis and block kriging interpolation were employed to analyze the spatial-temporal variations of soil salinity introduced by flood irrigation. Our results indicate that: (1) soil salinity in the two layers on different days can be well inverted from binary first-order equations of ECa at two coils (i.e., ECa1.0 and ECa0.5), demonstrating the feasibility of applying EM38-MK2 to estimate soil salinity in the field; and (2) soil salinity in the 0–20 cm layer significantly decreased during the first 15 days after flood irrigation with the greatest leaching rate of 88.37%, but tended to increase afterwards. However, the salinity in the 20–60 cm layer was persistently high before and after flood irrigation, with merely a brief decrease during the first 10 days after flood irrigation at the highest leaching rate of 40.74%. (3) The optimal semi-variance models illustrate that, after flood irrigation, the sill value (C0 + C) in the 0–20 cm layer decreased sharply, but the 20–60 cm Range of the layer significantly increased, suggesting that flood irrigation not only reduces the spatial variability of surface soil salinity, but also enhances spatial dependence in the 20–60 cm layer. (4) The correlation of the soil salinity between the two soil layers was very poor before flood irrigation, but gradually enhanced during the first 15 days after flood irrigation. Overall, for the study year, the first 15 days after flood irrigation was an optimal timing for cotton sowing when the leaching effects during flood irrigation were most efficient, and overrode the effects of evaporation and microtopography. Although not directly applicable to other years or regions, the electromagnetic induction surveys and spatiotemporal analysis of soil salinity can provide a rapid and viable guide to help determine optimal cotton sowing timing.

The Potential Use of Ground Conductivity Meters to Identify the Location of Seepages—Case Study of the Maniów Levee near Krakow, Poland

This paper presents an assessment of the potential usefulness of the Ground Conductivity Meter (GCM) method to locate seepage pathways in the Maniow levee zone near Kraków, Poland. We have realized this aim through geological recognition of the study area, which requires the implementation of GCM data inversion measured in the sounding version. The GCM measurements were performed along with the net of profiles using combined data from CMD Mini Explorer and CMD Explorer equipment. The methodology of the one-dimensional (1D) inversion of the GCM soundings located along profiles is presented in the article. The legitimacy of the inversion and the relationship of the results obtained in the form of conductivity sections along profiles with geology have been verified in detail. The inversion procedures were tested on the synthetic GCM soundings obtained from modeling processes, by using the electrical conductivity and thicknesses, known from the drilled formations and additionally based on DC-R sounding data. These soundings were performed at some selected reference points in the levee zone. We have used our software and IX1D Interpex software to calculate the forward modeling. Quantitative interpretation processed along the profiles has been proceeded by 1D inversion of GCM data at several referential points located close to boreholes and DC soundings. It was done to verify the correctness of the quantitative interpretation. The geoelectrical models, obtained in a section form, were correlated with the borehole lithology data, providing a reference geological structure in some places. As a result of the work mentioned above, the potential seepage zones were located on the conductivity sections. The thickness of the cohesive silty clay layer, lying near to the surface, in the seepage zones, was thin enough and less than a meter. When the water level in the Vistula river was high enough, water can flow in the noncohesive gravel layer occurring directly below the silty clays and lead to flooding on the landward side of the dams in the Maniow region.

FDEMtools: a MATLAB package for FDEM data inversion

Electromagnetic induction surveys are among the most popular techniques for non-destructive investigation of soil properties in order to detect the presence of either ground inhomogeneities or of particular substances. This work introduces a MATLAB package for the inversion of electromagnetic data collected by a ground conductivity meter. Based on a nonlinear forward model used to describe the interaction between an electromagnetic field and the soil, the software reconstructs either the electrical conductivity or the magnetic permeability of the soil with respect to depth, by a regularized damped Gauss-Newton method. The regularization part of the algorithm is based on a low-rank approximation of the Jacobian of the nonlinear model. Both the relaxation parameter and the regularization parameter are chosen by automatic procedures. The package allows the user to experiment with synthetic data sets and different regularization strategies, in order to compare them and draw conclusions.

Application of the conductive method in the engineering geology: Ruczaj district in Krak\xf3w, Poland, as a case study

The Ruczaj district in Kraków is the potential building area of high flat blocks for inhabitants. This area is built of the gypsum basement covered by the soil and impermeable clay beds with several meters of thickness. The flat blocks must be set on the textured gypsum layer. In the result of the rainfall and static pressure of the blocks, the water with SO42− increases up to the groundwater level, become the great threat for the flat blocks. The water creates specific hydrogeological conditions occurring in the zone of the building’s foundations. To eliminate the mentioned threat, we should determine precisely the thickness of the soil and impermeable clay as well as the depth of the gypsum basement. Based on the electromagnetic parameters of the geological formations, the Ground Conductivity Meter and DC resistivity methods were used to solve the mentioned problems.

Electromagnetic induction mapping at varied soil moisture reveals field-scale soil textural patterns and gravel lenses

Knowledge of the spatial distribution of soil textural properties is important for determining soil moisture storage and soil hydraulic transport properties. Capturing field heterogeneity without exhaustive sampling and costly sample analysis is difficult. Our objective was to employ electromagnetic induction (EMI) mapping in low apparent electrical conductivity (ECa) soils at varying soil water contents to capture time invariant properties such as soil texture. Georeferenced ECa measurements were taken using a ground conductivity meter on six different days where volumetric water content (θv) varied from 0.11 to 0.23. The 50 m × 50 m field included a subsurface gravelly patch in an otherwise homogeneous silt-loam alluvial soil. Ordinary block kriging predicted ECa at unsampled areas to produce 1-m resolution maps. Temporal stability analysis was used to divide the field into three distinct ECa regions. Subsequent ground-truthing confirmed the lowest conductivity region correlated with coarse textured soil parent materials associated with a former high-energy alluvial depositional area. Combining maps using temporal stability analysis gives the clearest image of the textural difference. These maps could be informative for modeling, experimental design, sensor placement and targeted zone management strategies in soil science, ecology, hydrology, and agricultural applications.

Frequency Management for Electromagnetic Continuous Wave Conductivity Meters.

Ground conductivity meters use electromagnetic fields for the mapping of geological variations, like the determination of water amount, depending on ground layers, which is important for the state analysis of embankments. The VLF band is contaminated by numerous natural and artificial electromagnetic interference signals. Prior to the determination of ground conductivity, the meter’s working frequency is not possible, due to the variable frequency of the interferences. Frequency management based on the analysis of the selected band using track-before-detect (TBD) algorithms, which allows dynamical frequency changes of the conductivity of the meter transmitting part, is proposed in the paper. Naive maximum value search, spatio-temporal TBD (ST-TBD), Viterbi TBD and a new algorithm that uses combined ST-TBD and Viterbi TBD are compared. Monte Carlo tests are provided for the numerical analysis of the properties for a single interference signal in the considered band, and a new approach based on combined ST-TBD and Viterbi algorithms shows the best performance. The considered algorithms process spectrogram data for the selected band, so DFT (Discrete Fourier Transform) could be applied for the computation of the spectrogram. Real–time properties, related to the latency, are discussed also, and it is shown that TBD algorithms are feasible for real applications.

Regularized solution of a nonlinear problem in electromagnetic sounding*

Non destructive investigation of soil properties is crucial when trying to identify inhomogeneities in the ground or the presence of conductive substances. This kind of survey can be addressed with the aid of electromagnetic induction measurements taken with a ground conductivity meter. In this paper, starting from electromagnetic data collected by this device, we reconstruct the electrical conductivity of the soil with respect to depth, with the aid of a regularized damped Gauss–Newton method. We propose an inversion method based on the low-rank approximation of the Jacobian of the function to be inverted, for which we develop exact analytical formulae. The algorithm chooses a relaxation parameter in order to ensure the positivity of the solution and implements various methods for the automatic estimation of the regularization parameter. This leads to a fast and reliable algorithm, which is tested on numerical experiments both on synthetic data sets and on field data. The results show that the algorithm produces reasonable solutions in the case of synthetic data sets, even in the presence of a noise level consistent with real applications, and yields results that are compatible with those obtained by electrical resistivity tomography in the case of field data.

Improving Quality Agricultural Practices in Tropical Environments through Integrated Geophysical Methods

Often, much attention is paid to things that do not majorly sustain life while the main pre requisite to living is usually left unattended to. Geoscience has been a tool used in solving the Earth's challenges both directly and indirectly. For instance, mining processes as well as hydrocarbon exploration has been aided extensively by the application of Geoscience, whereas Geophysics as a branch of Geoscience, which has proven worthwhile with so much importance in solving societal major need - Agriculture, is not gaining much attention.For agricultural application of geophysical methods, the three of all methods predominantly used are Electrical resistivity, Electromagnetic induction, and Ground Penetrating Radar (GPR). All these three methods are active, requiring artificial application of energy.Electrical resistivity method measures the electrical resistance for a bulk volume of soil which lies beneath the surface. This method basically reveals the subsurface electric field produced by the artificial application of electric current into the ground. An electromagnetic induction method measures the electrical conductivity for a bulk volume of soil directly beneath the surface. An instrument called ground conductivity meter is commonly employed for shallow electromagnetic induction investigations. With the Ground-penetrating radar method, an electromagnetic radio energy pulse is directed into the subsurface, followed by measurement of the elapsed time taken by the radar signal as it travels downward from the transmitting antenna, partially reflects off a buried feature, and eventually when it returns to the surface as it is picked up by a receiver. Past research indicates a wide range of indispensable uses for these three major geophysical methods employed in agriculture. Starting from soil water content monitoring using apparent soil electrical conductivity (ECa) measurements and Soil salinity assessment obtained with electrical resistivity and electromagnetic induction methods, followed by the use of GPR for updating and improving soil survey maps. These are used to evaluate soil property spatial variation.Agricultural geophysical measurements often tend to exhibit substantial variability by measuring soil electrical conductivity, soil dielectric constant (Water Content), spatial, horizontal and vertical changes. The Soil Water Content (SWC) controls important physical, chemical and biological processes such as plant growth, solute transport, rainfall, runoff, erosion, and ultimately pedogenesis. An understanding of the spatial and temporal variability in the soil properties (precision farming) using Geophysical methods will enhance the agricultural produce as well as soil management.Agricultural geophysics is the simplest and the most rapid method of identifying the nature of soil

Investigating the source of contaminated plumes downstream of the Alborz Sharghi coal washing plant using EM34 conductivity data, VLF-EM and DC-resistivity geophysical methods

Coal washing factories may create serious environmental problems due to pyrite oxidation and acid mine drainage generation from coal waste piles on nearby land. Infiltration of pyrite oxidation products through the porous materials of the coal waste pile by rainwater cause changes in the conductivity of underground materials and groundwater downstream of the pile. Electromagnetic and electrical methods are effective for investigation and monitoring of the contaminated plumes caused by coal waste piles and tailings impoundments. In order to investigate the environmental impact from a coal waste pile at the Alborz Sharghi coal washing plant, an EM34 ground conductivity meter was used on seven parallel lines in an E–W direction, downstream of the waste pile. Two-dimensional resistivity models obtained by the inversion of EM34 conductivity data identified conductive leachate plumes. In addition, quasi-3D inversion of EM34 data has confirmed the decreasing resistivity at depth due to the contaminated plumes. Comparison between EM34, VLF and DC-resistivity datasets, which were acquired for similar survey lines, agree well in identifying changes in the resistivity trend. The EM34 and DC-resistivity sections have greater similarity and better smoothness rather than those of the VLF model. Two-dimensional inversion models of these methods have shown some contaminated plumes with low resistivity.

Erratum to “Low induction number, ground conductivity meters: A correction procedure in the absence of magnetic effects” [Journal of Applied Geophysics, 75 (2011) 244–253

Erratum to “Low induction number, ground conductivity meters: A correction procedure in the absence of magnetic effects” [Journal of Applied Geophysics, 75 (2011) 244–253

Low induction number, ground conductivity meters: A correction procedure in the absence of magnetic effects

Abstract Ground conductivity meters, comprising a variety of coil–coil configurations, are intended to operate within the limits provided by a low induction number (LIN), electromagnetic condition. They are now routinely used across a wide range of application areas and the measured apparent conductivity data may be spatially assembled and examined/correlated alongside information obtained from many other earth science, environmental, soil and land use assessments. The theoretical behaviour of the common systems is examined in relation to both the prevailing level of subsurface conductivity and the instrument elevation. It is demonstrated that, given the inherent high level of accuracy of modern instruments, the prevailing LIN condition may require operation in environments restricted to very low (

Inversion of electrical conductivity data with Tikhonov regularization approach: some considerations

Electromagnetic induction measurements, which are generally used to determine lateral variations of apparent electrical conductivity, can provide quantitative estimates of the subsurface conductivity at different depths. Quantitative inference about the Earth's interior from experimental data is, however, an ill-posed problem. Using the generalised McNeill's theory for the EM38 ground conductivity meter, we generated synthetic apparent conductivity curves (input data vector) simulating measurements at different heights above the soil surface. The electrical conductivity profile (the Earth model) was then estimated solving a least squares problem with Tikhonov regularization optimised with a projected conjugate gradient algorithm. Although the Tikhonov approach improves the conditioning of the resulting linear system, profile reconstruction can be surprisingly far from the desired true one. On the contrary, the projected conjugate gradient provided the best solution without any explicit regularization ( a= 0) of the objective function of the least squares problem. Also, if the initial guess belongs to the image of the system matrix, Im(A), we found that it provides a unique solution in the same subspace Im(A).

Height-above-ground effects on penetration depth and response of electromagnetic induction soil conductivity meters

Ground conductivity meters such as the Geonics EM-31 and EM-38 are used to measure apparent soil conductivity. Various agriculturally useful soil properties can be estimated from these readings. For most surveys the instruments are placed as close to the ground as possible. One of the advantages of increasing the instrument height is that the depth of penetration of the instrument increases. However, increasing the height of the instruments also reduces the magnitude of the apparent conductivity readings. If conductivity varies in a field, the decrease in amplitude will decrease the size of the conductivity differences. This makes it harder to discriminate between soils with different conductivities when the conductivity differences are small. Creating a map of conductivity ratios which divide conductivity values throughout a field by a typical conductivity in one area of the field avoids this problem. Conductivity ratio maps make it easy to map spatial variations in conductivity. Increasing the instrument height has little effect on the ratio maps, even at heights of 1 m. This technique is most useful under non-saline conditions when conductivity differences between soil types may be small.

Mapping an Eighteenth-Century Wichita Village Site

Originally located in a Cross Timbers/short grass prairie ecotone on the Brazos River in central Texas, the Stone site (41ML38), the archaeological site of the late eighteenth-century Wichita (Tawakoni) village of Quiscat’s band, was investigated by Baylor University between 1999 and 2002. A 10 hectare geophysical survey (EM31 ground conductivity meter using a 1m grid interval) produced a village plan showing 75 circular anomalies (10-15 m in diameter), corresponding to the locations of round, grass-thatched lodges, arranged in three concentric ring clusters with outlying parallel rows. Archaeological excavation of one anomaly recovered post-molds arranged in a pattern that corresponded exactly in format (with three concentric rings: fireplace, 12 support posts, and outer walls) and size (9 m diameter) to the pattern derived from analysis of early twentiethcentury ethnographic photographs from Anadarko. The Wichita house served as a model for the layout of the village, and the pattern of house construction persisted from the 1770s–1905.

Assessment of diesel contamination in groundwater using electromagnetic induction geophysical techniques

Determining hydrocarbon plumes in groundwater is typically accomplished through the installation of extensive monitoring wells. Issues of scale and site heterogeneities tend to introduce errors in delineating the extent of contamination and environmental impact. In this study, electromagnetic induction survey was investigated as an alternative technique for mapping petroleum contaminants in the subsurface. The surveys were conducted at a coal mining site near Gillette, Wyoming, using the EM34-XL ground conductivity meter. Data from this survey were validated with known concentrations of diesel compounds detected in groundwater from the study site. Groundwater data correlated well with the electromagnetic survey data, which was used to generate a site model to identify subsurface diesel plumes. To our knowledge, this is one of the first studies to use electromagnetic survey techniques for mapping hydrocarbon contamination in groundwater. Results from this study indicate that this geophysical technique can be an effective tool for assessing subsurface petroleum hydrocarbon sources and plumes at contaminated sites.

The influence of soil moisture on magnetic susceptibility measurements

An important methodological question for magnetic susceptibility measurements is if a variation of the soil conductivity, as a result of a change in soil moisture, influences the measured susceptibility values. An answer to this question is essential because an accurate magnetic susceptibility mapping requires a grid of comparable magnetic susceptibility values, which indicate the magnetic iron-mineral contents of the soils. Therefore, in the framework of the MAGPROX project (EU-Project EVK2-CT-1999-00019), the study aims at investigating the influence of soil moisture and the possible correlation between magnetic susceptibility and electric conductivity. This approach was realised by model experiments in the laboratory and a field monitoring experiment, which was performed in an analogical manner as the model. For the laboratory experiment, a plastic tub with a water in- and outflow system and installed lines of electrodes was used. The measurements were carried out with layers of different magnetic material within the experimental sand formation under varying water saturation conditions. For the field experiment, which was carried out from July to December 2003, two test sites were selected. The magnetic susceptibility was measured by means of the recently developed vertical soil profile kappa meter SM400 and a commonly used Bartington MS2D probe. The electric resistivity was recorded using a 4-point light system (laboratory) and a ground conductivity meter EM38 (field). The knowledge of the resistivity of the sand formation enabled an estimation of porosity and water saturation in consideration of the Archie equations. The laboratory experiment results showed a very slight variation of measured magnetic susceptibility under different degrees of moisture, indicating mainly the influence from the diamagnetic contribution of the water volume. A measurement error in connection with the measurement method, for example caused by an interfering effect of soil conductivity variations, was not found. The authors conclude, that in practical use of the investigated instruments for topsoil magnetic susceptibility mapping in the field, the influence of soil moisture and resulting soil conductivity can be neglected, especially compared to the influence of the contact between measurement loop and soil. The study presented here verifies the magnetic susceptibility data reproducibility and comparability, which provides the basis for magnetic susceptibility monitoring. Additionally, new application approaches of magnetic susceptibility measurements were proposed, which show again the versatility and the potential of the method.

Golf Course Applications of Near-Surface Geophysical Methods: A Case Study

As of the year 2000, there were over 15,000 golf course facilities in the U.S.A. alone. The upkeep of these facilities requires continual maintenance and occasional remodeling. The superintendents and architects responsible for the maintenance and remodeling efforts need non-destructive tools for obtaining information on shallow subsurface features within parts of the golf course, particularly tees and greens. The subsurface features of importance include, but are not limited to, constructed soil layer characteristics and drainage system infrastructure. Near-surface geophysical methods can potentially provide a non-destructive means for golf course superintendents and architects to obtain the shallow subsurface information required to address their maintenance and remodeling concerns. This case study assessment of near-surface geophysical methods in regard to golf course applications focused on electromagnetic induction (EMI) and ground penetrating radar (GPR) techniques. The investigation employed two different EMI ground conductivity meters. Two GPR systems were also tested including the evaluation of antenna center frequencies ranging from [Formula: see text]. The study incorporated three separate sites. Measurements with both EMI and GPR were collected on a tee and a green at the Muirfield Village Golf Club in Dublin, Ohio, U.S.A. and on a practice green at the Golf Club of Dublin in Dublin, Ohio, U.S.A. GPR was also tested on a golf course green at the Guelph Turfgrass Institute & Environmental Research Centre in Guelph, Ontario, Canada. Results indicate that use of the appropriate EMI equipment can provide information on spatial changes of shallow apparent electrical conductivity [Formula: see text] within golf course green constructed soil layers. This [Formula: see text] data could potentially be employed to gauge constructed soil layer conditions, including wetness, salinity, etc., within different areas of a green. GPR proved quite capable of obtaining useful information on the golf course tee and greens that were studied, at least in regard to constructed soil layer thicknesses∕depths or their areal extent and in locating the subsurface drainage pipe systems present. For the GPR center antenna frequencies evaluated, ranging from [Formula: see text], all seemed to work relatively well for mapping tee and green constructed soil layer areal extent and drainage pipe locations. The higher frequency 900 and [Formula: see text] antennas appeared to work best for resolving thicknesses∕depths of constructed soil layers within the tee and greens investigated. In addition, computer modeling of synthetic GPR profiles provide valuable insight and help considerably with data interpretation. While more research is certainly warranted, near-surface geophysical methods, especially EMI and GPR, appear to show promise with respect to acquiring the data needed in golf course maintenance and remodeling applications.

Environmental geophysics investigations in urban areas

Dr John M. Reynolds, managing director and principal geophysicist at Reynolds Geo- Sciences, presents some case histories illustrating how the obstacles of noisy urban sites have been overcome to produce highly useful interpretable data sets, often far exceeding the expectations of the clients involved. Urban areas represent some of the most challenging environments in which to undertake geophysical investigations. Restricted space, the necessity for traffic management, high ambient noise (electrical and vibration), underground utilities, etc. all help to complicate the design and setting out of the geophysical profiles or grids. In many cases, such sites could not be investigated as the acquisition methods, the type of equipment and subsequent data processing software were not readily available. Over the last few years, significant changes in the capabilities of the equipment and software have permitted geophysical surveys to be undertaken in these hitherto inappropriate areas. The first case history at Field Road, Reading, Berkshire, was by far the largest, most complex and technically challenging. It shows how with very careful survey design, particular attention to data acquisition, and specialist data reduction and modelling, a labyrinth of shallow chalk mine galleries were mapped successfully using micro-gravity. The second involved a housing development in northwest London where the intrusive investigations had failed to satisfy the requirements of the Environment Agency, the environmental regulator in England and Wales (Scotland has a separate but similar regulatory body). Furthermore, the client and his engineering advisers were sceptical about the use of geophysics. Despite the technical difficulties of a complex partially developed site, the geophysical investigation demonstrated clearly the benefits of such a survey when integrated with intrusive investigations targeted on the basis of the geophysical survey. The client and his advisers became keen advocates of the use of geophysics once the results were made known. The third example is a complete contrast to the first two in that, despite the site being in a town, it comprised open space. The method used was the tried and tested and now very well established technique using a Geonics EM31 ground conductivity meter. (Detailed descriptions of geophysical methods discussed here have been presented by Reynolds (1997)). It demonstrates that even simple, long established techniques used very simply can produce some very clear and graphic results. The last case history involved the development of a former landfill site in south Wales. The 12.6 ha site was being cleared and earthworks to level the site were well in progress. At this late stage, it was suggested that steel drums might have been buried on the site but their location was unknown. A detailed geophysical investigation on the extremely busy construction site was undertaken using predominantly magnetic gradiometry and drum graves were located successfully and proven by excavation. The additional feature of all these case histories has been the involvement of what has subsequently become known as an ‘Engineering Geophysics Adviser’, an extremely experienced geophysicist (or group of geophysicists) independent of the geophysical contractor. This role has been advocated within the most recent guidelines for the use of engineering (and environmental) geophysics (McDowell et al., 2002).

Soil Water Content Monitoring Using Electromagnetic Induction

The use of electromagnetic (EM) induction measurements was evaluated to predict water content in the upper 1.50 m of a prototype engineered barrier soil profile designed for waste containment. Water content was monitored with a neutron probe, and bulk soil electrical conductivity was monitored with a Geonics EM38 ground conductivity meter at ten locations at approximately monthly intervals over a three-year period. A simple linear regression model accurately predicted average volumetric water content of the profile at any location at any time (R2=0.80,σ=0.009) and spatially averaged volumetric water content over the entire area at any time (R2=0.99,σ=0.003). Although some temporal drift was present in the model residual values, the impact on predicted water content was negligible. Therefore, once the model is calibrated with the neutron probe over a sufficient range of water contents, further neutron probe measurements may not be necessary. EM induction has several advantages over traditional water conten...

Inversion of Soil Conductivity Profiles from Electromagnetic Induction Measurements

Noninvasive electromagnetic (EM) induction techniques are used for salinity monitoring of agricultural lands and contaminant detection in soils and shallow aquifers. This study has four objectives. The first objective is to summarize an earlier linear model of the response of the EM38 ground conductivity meter and to discuss a more accurate nonlinear response model. The second objective is to verify experimentally whether the linear and nonlinear models derived for homogeneous media are valid in heterogeneous soil profiles. The third objective is to present an inverse procedure that combines the nonlinear model with Tikhonov regularization. The fourth objective is the experimental verification of inverse procedures with the linear and nonlinear models for inversion of soil conductivity profiles using aboveground electromagnetic induction measurements on fourteen saline Californian soil profiles. The linear and nonlinear models derived for homogeneous media are indeed valid in heterogeneous soil profiles. However, since the errors of the linear model are approximately double those of the nonlinear model, the latter is the preferred one. A small difference was found in the errors of the inverse procedures between the linear and nonlinear models. In this study, the inverse procedures with the linear model and with the nonlinear model produce equally good solutions at EM38 measurements below 100 mS m−1, while at higher electrical conductivities the inverse procedure with the nonlinear model appears to yield slightly better results. The inverse procedure with the linear model is preferred for all conductivities since it needs considerably less computer resources.