Geoscience Reference
In-Depth Information
3.2 SoIl SURveyInG USInG GpR
The application of GPR technology to study soils was begun in Florida by Benson and Glaccum
(1979) and was reported by Johnson et al. (1980). The basic objective of their studies was to deter-
mine if GPR could be used to accurately identify soil features and their depths for soil survey
purposes. How could this new geophysical tool be integrated into day-to-day soil mapping? They
determined that the radar could accurately locate soil features such as spodic and argillic horizons
as well as depth to the water table. Probably the most surprising result of the study was the brief time
it took to obtain the information as compared to traditional soil mapping. This was also documented
by Doolittle (1987) when he reported a decrease in cost (70 percent) and an increase in productivity
(210 percent) when he compared doing transects using GPR versus conventional methods
Thus, GPR was incorporated into the Florida Cooperative Soil Survey Program in 1981, as well
as in other cooperative soil survey programs, as a routine field tool to investigate subsurface features.
Much has been published in this respect. Here are some of the early publications on this subject:
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Study soil microvariability (Collins and Doolittle, 1987)
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Increase quality and efficiency of soil surveys (Collins et al., 1986; Doolittle, 1982, 1987;
Doolittle and Collins, 1995; Puckett et al., 1990; Schellentrager and Doolittle, 1991; Schel-
lentrager et al., 1988)
Determine thickness and characterize the depths of organic soil materials (Collins et al.,
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1986; Doolittle, 1983; Doolittle et al., 1990; Shih and Doolittle, 1984)
Chart the depths to relatively shallow (<2 m) water tables in predominantly coarse-textured
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soils (Shih et al., 1985)
Estimate depths to argillic (Asmussen et al., 1986; Collins and Doolittle, 1987; Hubbard
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et al., 1990; Truman et al., 1988a, 1988b) and spodic horizons (Collins and Doolittle, 1987;
Doolittle, 1987)
Improve soil-landscape modeling (Doolittle et al., 1988)
•
Most of the work cited above was done by the U.S. Department of Agriculture (USDA). In
fact, Doolittle and Asmussen (1992) published a review of the previous ten years (1981 to 1991) on
how the USDA (specifically the Soil Conservation Service, now known as the Natural Resources
Conservation Service, and the Agricultural Research Service) used GPR to investigate agricultural
soils. They reported the successful use of GPR to “map soils; chart the lateral extent and estimate
the depth to soil horizons; and delineate hard pans, water tables, bedrock, and unsaturated flow in
the vadose zone,” as well as to “assess soil compaction and plow pan development; variations in soil
texture, organic matter content, humification, and cementation; thickness of soil horizons, geologic
layers, and peat; and movement of water and contaminants in soils.” (p. 139)
Some state agricultural experiment stations were also using radar, and many were doing this in
collaboration with the USDA. At the same time, other countries were getting more involved with
the application of GPR to agricultural circumstances. An outcome was the establishment of the
GPR international radar conferences held every even year and alternating between being hosted in
the United States and other nations. At the same time, other commercial companies were develop-
ing and marketing GPR equipment which subsequently dropped the price of a standard unit. The
private sector has been slower in accepting this technology.
GPR has been used by archaeological, engineering, and environmental consulting companies,
but not to a great extent by agricultural businesses. One reason could be the soil conditions in which
GPR performs well, as discussed next.
3.3 dIReCt GpR ApplICAtIonS to AGRICUltURAl InveStIGAtIonS
Doolittle et al. (1998) used the State Soil Geographic (STATSGO; www.ncgc.nrcs.usda.gov/
products/datasets/statsgo/)
database to compare soil properties within the United States and Puerto
