Soil Classification: Past and Present - Soil Classification - page 20

Table 3.1 Families of Reddish Prairie Soils in the Southern Great Plains Correlation Area

Degree of
Weathering

Size of
Solum Family Stage Texture Class Drainage

Craig Maximal Medium Good Strong Medium

Dennis Medial Medium to

moderately fine

Good to moderately good Strong Medium

Hockley Maximal Moderately coarse Good to moderately good Strong Medium

Kirkland Medial Moderately fine Good to moderately good Medium Medium

La Bette Medial Loamy Good Medium Medium

Pratt Minimal Coarse Good Weak Medium

Teller Minimal Loamy Good Weak Medium

Tishomingo Medial Moderately coarse Good Strong Thin

Wilson Maximal Loamy Moderately good Strong Medium

and describe the morphology and properties of soil proÝles. This lack of standards hampered
pedology and resulted in classiÝcation schemes shrouded with cloudy concepts that lacked opera-
tional deÝnitions.
As an example, the U.S. 1938 classiÝcation system (USDA, 1938) followed the concepts of
zonal and azonal soils, lacked operational deÝnitions, and consequently failed to meet all the needs
of the soil science community. In the 1938 system, one of the zonal soils, Reddish Prairie Soils,
is described as dark-brown or reddish-brown soil grading through reddish-brown heavier subsoil,
medium acid. This description is very vague, and without the knowledge that these soils occur in
the southern Great Plains of the United States, the soil scientist might believe that these soils are
in several parts of the world. Aside from the indistinct categories within the 1938 scheme, the
system did not offer a means to differentiate soils both among taxa and within the same taxa. For
example, Table 3.1 illustrates the families from a card dated November 26, 1951, used presumably
by the correlators and Ýeld soil scientists to differentiate among the Reddish Prairie Soils. Obvious
deÝciencies include a lack of deÝnitions for column headings such as stage, degree of weathering,
and size of solum. Additionally, there are no operational deÝnitions to differentiate any of the
classes within the columns. This means that the differences among the differentiae, such as the
degrees of weathering, are based on judgment and experience. The terms may have valid meaning
to the local soil scientists. Soil scientists from different parts of the world, however, converging on
the southern Great Plains, could engage in interesting discussions, but likely not reach agreement
on whether a given soil exhibits medium or strong weathering. Furthermore, the differentiae are
deÝned in neither the (Soil Survey Staff, 1951) nor anywhere else.

The information in Table 3.1 is useful only to those who already have a familiarity with these
soils. The differentiae provide little value in distinguishing these soils, even for the most experienced
soil scientist.
Table 3.2 is also a card dated November 25, 1951, that attempts to provide facts about the Craig
soils. Again, the information is scant and provides little value for a soil scientist unfamiliar with
these soils or the area in general. Table 3.3 is a modern description of the same soil series.

Soil Survey Manual

MODERN SOIL CLASSIFICATION

After World War II, agriculture felt the effects of economic reconstruction and the expansion
of global markets, and there was a renewed interest in soil conservation and alternative land uses,
which helped invigorate soil survey activities. Soil scientists began identifying many new soils,
and classiÝcation systems needed to track all the newly recognized soils. The United States Soil
Conservation Service (now the Natural Resources Conservation Service), under the leadership of
Guy Smith, accepted the challenge and made giant strides in improving soil classiÝcation. Work
to develop a new U.S. soil classiÝcation system commenced in 1951.