PERMFILE62285

• Permit No: M2000041
• IBM Index Class Name: Permit File
• Doc Date: 3/13/2000
• Section_Exhibit Name: Application
• Media Type: D
• Archive: No

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g¢ SOIL SURVEY
solvent activity. Forest organic materials, combined
with the higher precipitation of the foothills and
mountains and the lo~v-calcium parent material, greatly
intensify leaching processes in these areas.
Small differences in vegetation can be seen on well-
drained soil in any given landscape. Where such differ-
ences occur, it may be difficult to determine the effect
of vegetation on soil formation. Such differences in
the vegetation are not necessarily the result of differ-
ences in soil characteristics, but ca~i reflect other en-
vironmental influences.
The activity of man has influenced the formation
of Rocky Ford soils and other irrigated soils. By pro-
viding irrigation water, man has changed the soil
climate, leading to an increase in the number of earth-
worms, the amount of microbial activity, and the
amount of plant residue. Intensive tillage, fertilizers,
and the silt-laden irrigation water have made Rocky
Ford soils different from nonirrigated soils. The surface
layer of Rocky Ford soils is 10 to 15 inches thick, and it
is darker colored and more fertile than that of non-
irrigated soils.
Re[iei
Relief refers to differences in elevation and inequali-
ties of the land surface, considered collectively. Relief
influences soil formation primarily through its effect
on drainage, runoff, and erosion and secondarily
through variations in exposure to the sun and wind and
in air drainage.
The relief of the plains part of the Pueblo Area is
gently undulating; some steep escarpments are on
terrace edges or below outcrops of limestone or sand-
stone. In the dry climate of the plains, the influence
of relief on soil formation is mostly through its effect
on erosion. In fine-textured soils, such as those of the
Midway, Razor, and Limon series, the devastating ef-
fect of erosion on profile development can be seen in
many places. Distinct differences in soil characteristics
in places are associated with relatively minor differ-
ences in slope and landforms within a given landscape.
Relief influences soil formation by virtue of its effect
on runoff. Where the total amount of rainfall is small,
slight differences in the supply of moisture can ac-
count for relatively great differences in vegetation
production and in soil morphology. Soils in concave
areas, where runoff tends to concentrate, show more
evidence of horizonation than soils on the surrounding
landscape. For example, Baca soils, which are in
slightly concave areas, have more horizon development
than Manvel soils.
On river and creek bottoms, where the relief is
nearly flat, there is a gradient that tends to produce
lateral movement of ground mater from the stream to
the surface of the soils. Nearly all of the poorly drained
to moderately well drained soils are on flood plains.
Soluble salts tend to accumulate in the surface of these
soils.
In the foothills and mountains, relief influences soil
formation through variation in aspect. North-facing
slopes have a more moist, cooler climate than south-
facing slopes. Mortenson soils in the Pueblo Area form
only on north-facing slopes in the foothills. Wetmore
and Pinata soils are mostly on north-facing slopes.
Slopes are steeper and differences in elevation greater
in the foothills and mountains than on the plains, and
there is more potential for runoff. However, more and
taller vegetation and rock fragments tend to offset
relief and reduce runoff.
Tune
The time required for soil horizons to differentiate
in parent material may range from several decades to
tens of thousands or even hundreds of thousands of
years, depending on the nature of the parent material,
the climate, and the relief. In the Pueblo Area the age
of the soil is usually related to the age of the landform.
The most recent or youngest landform occurs on flood
plains of streams. The soils that formed in alluvium on
flood plains have an A horizon but do not have a Ca
horizon or have only a faint one, as in the Glenberg
and Haverson soils. The Cascajo soils on high stream
terraces formed in older gravelly alluvium. They have
distinct A and Ca horizons. In loamy and fine-textured
parent material the degree of development of the B
horizon can be related to the age of the landform in
characteristics of structure, color, and clay content.
The B horizon of the oldest soils is usually redder and
has stronger structure and distinct, angular blocky
structure.
The age of soils can also be related to stages of
development. In the foothills and mountains in the
western part of the survey area, the factors of climate,
parent material, and living organisms reinforce each
other so that soil horizons differentiate more rapidly
than on the plains. The landform may or may not be
older than those on the plains, but because of the more
rapid soil-forming processes the soils are in a more
advanced stage of development.
Youthful soils resemble the parent material in which
they form. Mature soils have distinct horizons that lie
one above the other and are parallel to the earth's
surface.
Classification of the Soils
Soils are classified so that we can more easily re-
member their significant characteristics. Classification
enables us to assemble knowledge about the soils, to
see their relationship to one another and to the whole
environment, and to develop principles that help us to
understand their behavior and their response to manip-
ulation. First through classification, and then through
use of soil maps, we can apply our knowledge of soils
to specific fields and other tracts of land.
The narrow categories of classification, such as those
used in detailed soil surveys, allow us to organize and
apply knowledge about soils in managing farms, fields,
and woodlands; in developing rural areas; in engi-
neering work; and in many other ways. Soils are
placed in broad classes to facilitate study and compari-
son in large areas, such as countries and continents.
The system of soil classification currently used was
adopted by the National Cooperative Soil Survey in
1965. Because this system is under continual study,
readers interested in developments of the current sys-
tem should search the latest literature available (10).
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