Soil Survey of Runnels County, Texas Page: 2
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SOIL SURVEY
landscape. Soils of one series can differ somewhat in
the texture of the surface layer and in slope, stoni-
ness, or some other characteristic that affects use of the
soils by man.
Many soil series contain soils that differ in the tex-
ture of their surface layer. According to such differences
in texture, separations called soil types are made. Within
a series, all the soils leaving a surface layer of the same
texture belong to one soil type. Miles fine sandy loam
and Miles loamy fine sand are two soil types in the Miles
series. The difference in the texture of their surface layers
is al)pparent from their names.
Some soil types vary so much in slope, degree of ero-
sion, number andl size of stones, or some other feature
affecting their use, that practical suggestions about their
management could(l not )e made if they were shown on
the soil map as one unit. Such soil types are divided into
soil phases. The name of a soil phase indicates a feature
that affects management. For example, Miles fine sandy
loa 11, 0 to 1 percent slopes, is onea of two phases of Miles
fine sandy loam, a soil type that has a slope range of
0 to 3 percent.
After a guide for classifying and naming the soils
had been worked out, the soil scientists drew the bound-
aries of the individual soils on aerial photographs. These
photographs show woodlands, buildings, field borders,
trees, and other details that help in drawing boundaries
accurately. The soil map at the back of this survey was
prepared from the aerial photographs.
The areas shown on a soil map are called mapping
units. On most maps detailed enough to be useful in
planning management of farms and fields, a map-
ping unit is nearly equivalent to a soil type or a
phase of a soil type. It is not exactly equivalent, be-
cause it is not practical to show on such a map all
the small, scattered bits of soil of some other kind that
have been seen within an area that is dominantly of a
recognized soil type or soil phase.
In preparing some detailed maps, the soil scientists
have a l)prob)lel of delineating areas where different
kinds of soils are so intricately mixed or occur in such
small individual tracts that it is not practical to show
them separately on the map. They show such a mixture
of soils as one mapping unit and call it a soil com-
plex. Ordinarily, a soil complex is named for the major
kinds of soils in it, for example, Talpa-Kavett com-
plex.
Another kind of mapping unit is the undifferentiated
group, which consists of two or more soils that may occur
together without regularity in pattern or relative pro-
portion. The individual tracts of the component soils could
be shown separately on the map, but the differences
between the soils are so slight that the separation is not
important for the objectives of the soil survey. An exam-
ple is Colorado and Yahola soils.
Most surveys include areas where the soil material is
so rocky, so shallow, or so frequently worked by wind
and water that it cannot be classified by soil series.
Such an area is shown on the map like other mapping
units, but it is given a descriptive name, such as Rough
stony land, and is called a land type.While a soil survey is in progress, samples of soils
are taken, as needed, for laboratory measurements and
for engineering tests. Laboratory data from the same
kinds of soils in other places are assembled. Data on
yields of crops under defined practices are assembled
from farm records and from field and plot experiments
on the same kinds of soils. Yields under defined man-
agement are estimated for all the soils.
But only part of a soil survey is done when the soils
have been named, described, and delineated on the
map and the laboratory data and yield data have been
assembled. The mass of detailed information then needs
to be organized in such a way that it is readily useful
to different groups of readers, among them farmers,
ranchers, engineers, and homeowners. Grouping soils
that are similar in suitability for each specified use
is the method of organization commonly used in soil
surveys. The soil scientists set uip trial groups based on
the yield and practice tables and other data. They test
these groups by further study and by consultation with
farmers, agronomists, engineers, and others; then they
adjust the groups according to the results of their
studies and consultation. Thus, the groups that are
finally evolved reflect up-to-date knowledge of the soils
and their behavior under present methods of use and
management.
General Soil Map
The general soil map at the back of this publication
shows, in color, the soil associations in Runnels Coun-
ty. A soil association is a landscape that has a dis-
tinctive proportional pattern of soils. It normally
consists of one or more major soils and at least one
minor soil, and it is named for the major soils. The
soils in one association may occur in another, but in a
different pattern.
A map showing soil associations is useful to people
who want a general idea of the soils in a county, who
want to compare different parts of a county, or who
want to know the location of large tracts that are suit-
able for a certain kind of farming or other land use.
Such a map is not suitable for planning the manage-
ment of a farm or field, because the soils in any one
association ordinarily differ in slope, depth, drainage, and
other characteristics that affect management.
The seven soil associations in Runnels County are de-
scribed in the paragraphs that follow.
1. Portales-Potter-Mereta association
Nearly level to undulating, loamy soils that ate mod-
erately deep to very shallow over caliche; on outwash
plains
This association occupies broad areas on upland in
most parts of the county. The gradient is mainly 0
to 8 percent but in places is as much as 20 percent.
The total area is about 40 percent of the county.
This association is about 37 percent Portales soils, 23
percent Potter soils, 21 percent Mereta soils, and 19 per-2
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Wiedenfeld, C. C.; Barnhill, L. J. & Novosad, Clifford J. Soil Survey of Runnels County, Texas, book, March 1970; Washington D.C.. (https://texashistory.unt.edu/ark:/67531/metapth224548/m1/6/?rotate=90: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.