Soil Survey of Houston County, Texas Page: 33

                                
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Detailed Soil Map Units

The map units delineated on the detailed soil
maps in this survey represent the soils or
miscellaneous areas in the survey area. The map unit
descriptions in this section, along with the maps, can
be used to determine the suitability and potential of a
unit for specific uses. They also can be used to plan
the management needed for those uses.
A map unit delineation on a soil map represents an
area dominated by one or more major kinds of soil or
miscellaneous areas. A map unit is identified and
named according to the taxonomic classification of
the dominant soils. Within a taxonomic class there
are precisely defined limits for the properties of the
soils. On the landscape, however, the soils are
natural phenomena, and they have the characteristic
variability of all natural phenomena. Thus, the range
of some observed properties may extend beyond the
limits defined for a taxonomic class. Areas of soils of
a single taxonomic class rarely, if ever, can be
mapped without including areas of other taxonomic
classes. Consequently, every map unit is made up of
the soils or miscellaneous areas for which it is named
and some minor components that belong to
taxonomic classes other than those of the major
soils.
Most minor soils have properties similar to those of
the dominant soil or soils in the map unit, and thus
they do not affect use and management. These are
called noncontrasting, or similar, components. They
may or may not be mentioned in a particular map unit
description. Other minor components, however, have
properties and behavioral characteristics divergent
enough to affect use or to require different
management. These are called contrasting, or
dissimilar, components. They generally are in small
areas and could not be mapped separately because
of the scale used. Some small areas of strongly
contrasting soils or miscellaneous areas are
identified by a special symbol on the maps. The
contrasting components are mentioned in the map
unit descriptions. A few areas of minor components
may not have been observed, and consequently they
are not mentioned in the descriptions, especially
where the pattern was so complex that it was
impractical to make enough observations to identify

all the soils and miscellaneous areas on the
landscape.
The presence of minor components in a map unit
in no way diminishes the usefulness or accuracy of
the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the
landscape into landforms or landform segments that
have similar use and management requirements. The
delineation of such segments on the map provides
sufficient information for the development of resource
plans. If intensive use of small areas is planned,
however, onsite investigation is needed to define and
locate the soils and miscellaneous areas.
An identifying symbol precedes the map unit name
in the map unit descriptions. Each description
includes general facts about the unit and gives the
principal hazards and limitations to be considered in
planning for specific uses.
Soils that have profiles that are almost alike make
up a soil series. Except for differences in texture of
the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness,
and arrangement.
Soils of one series can differ in texture of the
surface layer, slope, stoniness, salinity, degree of
erosion, and other characteristics that affect their use.
On the basis of such differences, a soil series is
divided into soil phases. Most of the areas shown on
the detailed soil maps are phases of soil series. The
name of a soil phase commonly indicates a feature
that affects use or management. For example,
LaCerda clay loam, 5 to 15 percent slopes, is a
phase of the LaCerda series.
Some map units are made up of two or more major
soils or miscellaneous areas. These map units are
complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or
miscellaneous areas in such an intricate pattern or in
such small areas that they cannot be shown
separately on the maps. The pattern and proportion
of the soils or miscellaneous areas are somewhat
similar in all areas. Freestone-Derly complex, 0 to 2
percent slopes, is an example.
Table 4 gives the acreage and proportionate extent
of each map unit. Other tables give properties of the