The use of electromagnetic induction techniques in soils studies

TLDR: Electromagnetic induction (EMI) has been used to characterize the spatial variability of soil properties since the late 1970s as mentioned in this paper, which can provide a more complete characterization of the spatial variations in soil properties than traditional sampling techniques.

About: This article is published in Geoderma.The article was published on 2014-07-01 and is currently open access. It has received 301 citations till now. The article focuses on the topics: Digital soil mapping & Soil map.

Figures

Fig. 4. These images show the spatial distribution of ECa for two depth intervals (left-hand plots) and classes of salt-affected soils (right-hand plot) for a field in southwestern North Dakota. The classes of salt-affected soils are based on both SAR and soil salinity levels for the 0 to 90 cm soil column as predicted by stochastic models of ECa (Heilig et al., 2011).

Fig. 5. This 3D simulation shows the spatial distribution of ECa and the locations of saline seeps within an area of dryland farming in north central Montana (Doolittle, 2013).

Fig. 8. Results of two time-lapsed EMI surveys that were conductedwithin a small catchment located in central Pennsylvania in the fall (dry conditions) and spring (wet conditions) using an EM38 meter with a density of about 750 measurements per ha (Doolittle et al., 2012).

Fig. 1. Four EMI sensors commonly used in soil investigations are the DUALEM-1 meter, the DUALEM-2 meter, the EM38-MK2 meter, and the Profiler EMP-400.

Table 1 Taxonomic classification of soils identified in Fig. 6a and b.

Table 2 Taxonomic classification of soils identified in Fig. 6c.

Frequently asked questions

Q1. What are the contributions in "The use of electromagnetic induction techniques in soils studies" ?

Doolittle et al. this paper used EMI to estimate the apparent electrical conductivity ( ECa ) of the subsurface without direct contact with the sampled volume. 

Q2. Why are salts concentrated near the soil surface?

Because of upward leaching and evaporative processes, salts are concentrated near the soil surface in groundwater discharge sites (seeps) (Richardson and Williams, 1994). 

Q3. What is the ECa of the surface layers?

The higher concentration of soluble salts in surface layers results in higher ECa and inverted salt profiles (ECa is highest in surface layers and decreases with increasing depth). 

Q4. What is the common use of EMI?

A major challenge in using EMI to map soil salinity has been the conversion of apparent conductivity(ECa) into the conductivity of the saturated paste extract (ECe); the most commonly used measure of soil salinity. 

Q5. What are the advantages of EMI in soils?

Recent improvements in instrumentation and integration with other technologies (global-positioning systems (GPS), data processing software, and surface mapping programs) have fostered the expanded use of EMI in soils applications. 

Q6. What was the evolution of EMI sensors?

By the mid- to late-1990s, the maturation of GPS and its integration with EMI sensors and data loggers revolutionized the collection of ECa data. 

Q7. What is the effect of EMI on soil mapping?

The effectiveness of EMI as a soil mapping tool will depend upon the degree to which differences in the physical and chemical properties that affect ECa correspond to differences in soils. 

Q8. What are the main types of sampling methods used in hydropedological studies?

Point-sampling methods (such as soil pits, monitoring wells, core samples, and soil moisture probes) provide detailed, but highly site-specific soil and hydrologic data. 

Q9. How did Anderson-Cook et al. (2002) classify the soil type?

Using the ECa data, Anderson-Cook et al. (2002) were able to correctly classify the soil type with an accuracy of greater than 85%. 

Q10. What is the main contribution of EMI surveys?

A major contribution of EMI surveys has been the identification and delineation of small included areas of dissimilar soils within soil polygons that have been mapped on second-order soil maps (Fenton and Lauterbach, 1999), although some common EMI sampling methods tend to represent soils that occupy a large percentage of the area within a field more representatively than soils that occupy small areas (Brevik, 2012). 

Q11. What is the reason for the use of EMI in soils?

The impetus for this expanded use has been the need for more accurate soil maps than those provided by traditional mapping techniques (Batte, 2000; Brevik et al., 2003, 2012) and the demonstrated efficiency of EMI to improve the accuracy and reliability of soil maps and provide more detailed information on soils and soil properties.⁎ 

Q12. What are the spatial ECa patterns in the catchment?

the spatial ECa patterns shown in Fig. 8 suggest two major, temporally-stable soil-landscape units within the catchment: the valley floor and higher-lying slope components.