Eric Stoner Soils (781701)
Objective:
The general objective is to define quantitatively the relationships between
soil reflectance and physiochemical properties of soils of significance to
agriculture and engineering. Selection of soil samples with a wide
rangeof important soil characteristics by statistical stratification of
continental United States climatic zones permits the evaluation of climatic
and genetic effects on the relationships between multispectral reflectance
and these soil properties. A further objective is to define the relationships
sufficiently to design further research to quantify the contributions which
different soil components make to the multispectral characteristics of
specific soils.
Method:
Because of the need to provide a uniform moisture condition for
spectroradiometric analysis of the prepared soil samples, a procedure
was chosen which creates a one-tenth bar soil moisturetension on all the
soil samples (3,5). Two asbestos tension tables were constructed and a
100 cm column of water was established to create a soil moisture tension
for up to 56 soil samples at one time. Sample holders were designed and
constructed of plastic rings 2 cm deep by 10 cm in diameter with 60 mesh
brass strainer cloth stretched taut and fastened in a countersunk groove in
one end. Sample holders were painted with non-reflecting black paint to
reduce unwanted reflection external to the target of interest. After
saturation of the soil filled, leveled sample holders for about four hours,
the samples were placed on the tension tables for 24 hours in order to
reach equilibrium. The one-tenth bar moisture tension was desirable
mainly for the ease with which large numbers of samples could be
prepared at uniform moisture characteristics. Shortly after placement of
each sample holder on the sample table of the reflectometer for spectral
readings, a portion of the sample was transferred to a moisture tin,
weighed, dried in a forced air oven at 105 C, weighed again, and
moisture content reported as percentage of oven dry weight.
Quantification of Soil Properties
Modern soil classification systems emphasize the importance of
information about the quantitative compositions of soils. In order to
differentiate among soil groups, it is necessary to rely on laboratory
measurements of selected soil properties. Physical, chemical, and
engineering determinations of most soil properties follow well established
procedures of laboratory analyses. Certain of these soil properties are
selected as diagnostic criteria in the soil classification process, based on
their importance in understanding the genesis of the soil. By a procedure
of empirical correlation, critical limits between sets of soils are
established, designed to reflect the influence of the soil forming factors of
climate, parent material, relief, biological activity, and time.
Quantitative measurements of soil spectral properties have become
available as a diagnostic tool for the soil scientist with the advent of such
instruments as the Exotech Model 20C spectroradiometer. However, the
climatic and genetic effects on the relationships between measured
spectral properties and specific chemical, physical, and biological
properties of the soil are not well understood. Whereas soil color is used
as diagnostic criterion in the U.S. Soil Taxonomy (7), the determination of
soil color by comparison with a color chart continues to be a rather
nonquantitative and subject procedure. Spectral characterization of soil
"color" by means of quantitative spectroradiometric measurements may
add to the precision with which soils can be differentiated. With this
increased precision of soil spectral characterization, the relationships with
the more important diagnostic soil characteristics or qualities that are not
so easily and accurately observed may be better understood.
EXPERIMENTAL APPROACH
Stratification and Sampling
Approximately 250 soils, representing a statistical sampling of the more
than 10,000 soil series in the United States were selected for this
investigation. Selections were made from a list of the more than 1300
Benchmark soil series representing those soils with a large geographic
extent and whose broad range of characteristics renders these soils so
widely applicable for study. Stratification of soil sampling was based on
series type location within climatic zones. Climatic strata included the
frigid, mesic, thermic, and hyperthermic soil temperature regimes as
defined by the U.S. Soil Taxonomy (2,6,7) as well as the perhumid,
humid, subhumid, semiarid, and arid moisture regions as identified by
Thornthwaite's 1948 Moisture Index (8). A random selection procedure
was used within each stratified climatic zone to select a number of soils
series approximately in proportion to the geographic extent of that region.
Resulting sample distribution by climatic region for the soils actually
received is shown in Table 1. Considerations were also made to include
soils which represent the major parent material categories and the ten
soils orders of the U.S. Soil Taxonomy (7). Table 2 presents the
distribution of the Benchmark soil series on-hand according to soil parent
material. As can be seen in Table 3, the distribution to Benchmark soils
used for this study is very similar to the areal extent of the nine soil orders
found in the continental United States (Oxisols being absent in the
contiguous states).
Table 1. Distribution of soils by climatic region
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Number of Benchmark
Climatic Region Soil Series
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1. Perhumic Mesic 6
2. Humid Frigid 18
3. Humid Mesic 37
4. Humid Thermic 30
5. Humid Hyperthermic 6
6. Subhumid Frigid 21
7. Subhumid Mesic 23
8. Subhumid Thermic 18
9. Subhumid Hyperthermic 2
10. Semiarid Frigid 9
11. Semiarid Mesic 24
12. Semiarid Thermic 10
13. Semiarid Hyperthermic 5
14. Arid Frigid 2
15. Arid Mesic 16
16. Arid Thermic 12
17. Arid Hyperthermic 1
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240 total
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Table 2. Distribution of soils by parent material
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Parent Material Number of
Benchmark Soil Series
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Rocks weathered in place
Igneous 10
Sedimentary 27
Metamorphic 1
Soft rock residuum 5
Transported materials
Alluvium (general) 38
Calcareous 11
Non-calcareous 15
Colluvium 3
Lacustrine 4
Marine sediments 16
Loess 29
Other eolian sediments 8
Glacial drift
Till 29
Calcareous till 5
Glaciofluvial deposits 4
Glacial outwash 4
Glaciolacustrine materials 2
Organic materials 2
Loamy sediments 17
Silty sediments 4
Calcareous silt loam 3
Marsh deposits 1
Pedisediments 2
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240 total
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Table 3. Distribution of soils by Soil Order.
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Benchmark Soils United States Extent
Number Percent Percent
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Mollisol 73 30.4 24.6
Alfisol 40 16.7 13.4
Entisol 39 16.2 7.9
Aridisol 25 10.4 11.5
Ultisol 22 9.2 12.9
Inceptisol 18 7.5 18.2
Spodosol 15 6.2 5.1
Vertisol 4 1.7 1.0
Histosol 4 1.7 0.5
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total 240
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Acquisition of Soil Samples
The Soil Survey Investigation Division of the Soil Conservation Service
(USDA) cooperated with LARS in the collection of field samples from 39
states. Duplicate field samples were collected for all Benchmark soil
series requested: one sample from a site near the type location for the
current official series, and one sample from a site located from one to 32
kilometers from the first site and in a different mapping delineation. Soil
Conservation Service field survey personnel were responsible for sample
collection of Benchmark soils in their locality. Of the original list of
approximately 250 Benchmark soils requested, the Soil Conservation
Service has collected, properly identified, and forwarded 240 Benchmark
soils, or 480 duplicate soil samples to LARS. This excellent response of
over 95 percent of the requested samples forms an outstanding collection
of soil samples for detailed chemical, physical, and spectral analysis. All
samples conform to the central concept of each individual soil series as
each soil would be identified and mapped by an experienced soil
surveyor in the field.
Preparation of Soils for Analysis
After receipt of the soil samples and initial data logging, samples were
dried, crushed, and sieved to remove all particles larger than 2 mm
diameter. Cardboard containers were used to store subsamples of each
soil sample for chemical, physical, spectral, and engineering
determinations.
Spectral Measurements
The Exotech Model 20C was used in an indoor configuration with a
bidirectional reflectance factor reflectometer (1,4) in order to obtain
spectral readings in the 0.52-2.3 um wavelength range. The illumination
source was a 1000 watt tungsten iodine coiled filament lamp which
transfers a highly collimated beam by means of a paraboloidal mirror to
the sample-viewing plane. Detector height above the sample was 2.4 m,
and a 3/4 field of view required that the sample holder be approximately
10 cm in diameter.
Soil Measurements
Other measurements made of the soil are listed in Table 4.
Table 4. Soil characteristics and descriptions that may be
included in the data base.
Taxonomic Site
Information Characteristics
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Order Soil series name
Suborder Horizon designation
Great group Moisture regime
Subgroup name Drainage class
Particle size class Slope
Contrasting particle size class Erosion phase
Mineralogy class Physiographic position
Temperature regime Parent material
Other modifiers Soil evaluation
Natural vegetation or crop
Site location
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Physical Chemical
Characteristics Characteristics
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Soil moisture tension Organic carbon
Water content Extractable bases:
Munsell color (moist) calcium
Textural class designation magnesium
USDA particle size distribution: sodium
sand content potassium
silt content extractable acidity
clay content cation exchange capacity
very coarse sand base saturation
coarse sand Iron oxide
medium sand Aluminum oxide
fine sand Manganese dioxide
very fine sand
coarse silt Available phosphorus
fine silt Available potassium
Erosion factor
Wind erodibility group
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Engineering
Characteristics
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Liquid limit Compression index
Plastic limit ASTM particle size distribution:
Plasticity index medium sand
Activity fine sand
Liquidity index fines
Shrinkage limit Specific gravity
Shrinkage ratio AASHO soil classification
Volumetric shrinkage Unified soil classification
Linar shrinkage
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Additional Information
Additional information about the experiment including detailed chemical,
physical, and spectral soil properties can be found in reference 9.
References
1. DeWitt, D. P. and B. F. Robinson. 1976. Description and evaluation
of a bidirectional reflectance factor reflectometer. Information Note
091576, Laboratory for Applications of remote Sensing, Purdue
University, West Lafayette, IN.
2. FAO-UNESCO. 1975. Soil map of the world, Vol. II: North America.
United Nations Educational, Scientific, and Cultural Organization, Paris.
3. Jamison, V. C. and I. F. Reed. 1949. Durable asbestos tension
tables. Soil Science 67:311-318.
4. Leamer, R. W., V. I. Meyers and L. F. Silva. 1973. A spectroradiometer
for field use. Rev. Sci. Instrum. 44:611-614.
5. Leamer, R. W. and B. Shaw. 1946. A simple apparatus for measuring
noncapillary prorsity on an extensive scale. J. Amer. Soc. Agron.
33:1103-1108.
6. Smith, Guy D., Ranklin Newhall and Luther H. Robinson. 1964. Soil
temperature regimes, their characteristics and predicatability. SCS-TP-
144. Soil Conservation Service. U.S. Dept. of Agriculture Washington, D.C.
7. Soil Survey staff. 1975. Soil taxonomy -- a basic system of soil
classification for making and interpreting soil survey. Soil Conservation
Service. U.S. Dept. of Agric. Agriculture Handbook No. 436, Washington,
D.C.
8. Thornthwaite, C. W. 1948. An approach toward a rational
classification of climate. Geograph. Rev. 38:55-94.
9. Stoner, E. R., M. F. Baumgardner, L. L. Biehl, and B. F. Robinson.
1980. Atlas of Soil Reflectance Properties. Research Bulletin 962.
Agriculture Experiment Station, Purdue University, West Lafayette,
Indiana.
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