SOILS SPECTRA OVERVIEW

Soil samples representing all major soil types were provided by Laurence E. 
Brown (USDA National Soil Survey Laboratory, Lincoln, Nebraska), and sample 
numbers are those assigned by the Soil Survey Laboratory.  One sample (0015) 
was provided by M. B. Satterwaite (Army Corps of Engineers Center for Remote 
Sensing, Fort Belvoir, VA).

A general description of the soil has been used for the soil name, rather than the 
modern classification system of the USDA Soil Conservation Service.  This 
classification system, which is little understood outside the field of soil science, is 
used for Class and Subclass.  Those wishing to understand this classification 
system are referred to Foth and Schafer (1980).

Detailed descriptions are given for most soils, typically abstracted from Soil 
Survey Laboratory documentation.  In these descriptions, percentages of sand, 
silt, and clay refer to particle size ranges as defined by that laboratory.  Clay size 
is less than 0.002 mm; silt size ranges from 0.002 to 0.05 mm; and sand size 
ranges from 0.05 to 2 mm.  When available, clay mineralogy was determined 
semi-quantitatively from the relative intensities of X-ray diffraction peaks, while 
coarse mineralogy refers to the composition of sand and silt size fractions as 
determined by petrographic microscope.  Percent organic carbon was obtained 
by wet combustion analysis (Walkley-Black), and can be converted to an 
estimate of organic matter by multiplying by 1.7.  

Soil samples were measured air dried and sifted through a 1 mm screen to break 
up clods and exclude stones and twigs.  Many soils have also been measured 
after packing, which typically has very little effect on their spectra.


REFERENCES

Foth, H. D., and Schafer, J. W., 1980, Soil Geography and Land Use, Wiley, New 
York, 484 pp.