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<br />LAMAR AND DELTA COUNTIES, TEXAS
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<br />during the course of the survey. New interpretations are
<br />added to meet I,ocal needs, mainly through field observa-
<br />tions of different kinds of soil in different uses under
<br />different levels of management. Also, data are assem-
<br />bled from other sources, such as test results, records,
<br />field experience, and information available from state
<br />and local specialists. For example, data on crop yields
<br />under defined practices are assembled from farm rec-
<br />ords and from field or plot experiments on the same
<br />kinds of soil.
<br />But only part of a soil survey is done when the soils
<br />have been named. described, interpreted, and delineated
<br />'on aerial photographs and when the laboratory data and
<br />other data have been assembled. The mass of detailed
<br />information then needs to be organized so that it is
<br />readily available to different groups of users, among
<br />them farmers, managers of rangeland and woodland,
<br />engineers, planners, developers and builders, home-
<br />buyers, and those seeking recreation.
<br />
<br />General soil map for broad land use
<br />
<br />planning
<br />
<br />The general soil map at the back of this publication
<br />shows, in color, map units that have a distinct pattern of
<br />soils and of relief and drainage. Each map unit is a
<br />unique natural landscape. Typically, a map unit consists
<br />of one or more major soils and some minor soils. It is
<br />named for the major soils. The soils making up one unit
<br />can occur in other units but in a different pattern.
<br />The general soil map provides a broad perspective of
<br />the soils and landscapes in the survey area. It provides a
<br />basis for comparing the potential of large areas for gen-
<br />eral kinds of land use. Areas that are, for the most part,
<br />suited to certain kinds of farming or to other land uses
<br />cen be Identified on the map. Likewise, areas of soils
<br />having properties that are distinctly unfavorable for cer-
<br />tain land uses can be located.
<br />Because of its small scale, the map does not show the
<br />kind of soil at a specific site. Thus, it is not suitable for
<br />planning the management of a farm or field or for select-
<br />ing a site for a road or building or other structure. The
<br />kinds of soil in anyone map unit differ from place to
<br />place In slope, depth, stoniness, drainage, or other char-
<br />acteristics that affect their management.
<br />The soils in the survey area vary widely in their poten-
<br />tial for major land uses. Table 2 shows the extent of the
<br />map units shown on the general soil map and gives '
<br />general ratings of the potential of each, in relation to the
<br />other map units, for major land uses. Soil properties that
<br />pose limitations to the use are indicated. The ratings of
<br />soil potential are based on the assumption that practices
<br />in common use in the survey area are being used to
<br />'overcome soil limitations. These ratings ref/ect the ease
<br />of overcoming the soil limitations and the probability of
<br />soil problems persisting after such practices are used.
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<br />Each map unit is rated for cultivated farm crops, pas-
<br />ture and hay, renge, woodland, woodland grazing, urban
<br />uses, and recreatIon. Cultivated farm crops are those
<br />grown extensively by farmers in the survey area. Pasture
<br />and hay consist of grasses established for grazing or
<br />cutting. Woodland refers to land that is producing either
<br />trees native to the area or Introduced species. Woodland
<br />grazing is using grassy areas in woodland for grazing.
<br />Urban uses include residential, commerciai, and industri-
<br />al developments. Recreation includes campsites, picnic
<br />areas, ballfields, and other areas that are subject to
<br />heavy foot traffic and areas used for nature study and as
<br />wilderness.
<br />
<br />DescrIptions of the general soli map units
<br />
<br />1. Houston Black-Leson-Helden
<br />
<br />Nearly level to gently sloping, velJl Slowly permeable,
<br />clayey soils on uplandS
<br />
<br />This map unit consists of clayey prairie soils that crack
<br />when dry. Siopes are 0 to 5 percent (fig. 1).
<br />This unit makes up about 32 percent of the survey ,
<br />area. It Is about 32 percent Houston Black soils, 18
<br />percent Leson soils, 12 percent Heiden soils, and 38
<br />percent other soils.
<br />Houston Black soils are on sides and tops and at the
<br />foot of ridges. These soils are moderately weil drained.
<br />They are moderately alkaline throughout. The surface
<br />layer is very dark gray clay about 5 inches thick. Be-
<br />tween depths of 5 and 23 inches, the soil is black clay.
<br />Between depths of 23 and 38 inches, the soil is very
<br />dark clay. Between depths of 38 and 51 inches, the soil
<br />Is olive gray clay that has light olive brown and gray
<br />mottles. Between depths of 51 and 77 inches, the soil is
<br />light olive brown clay over grayiSh brown clay that has
<br />mottles of yellow, gray, and brownish yellow. The under-
<br />lying material is brownish yeilow and light brownish gray,
<br />stratified shaly clay to a depth of 80 inches.
<br />Leson soils are on tops and sides of ridges. These
<br />soils' are moderately well drained. The surface layer is
<br />black, slightly acid clay about 20 inches thick. Between
<br />depths of 20 and 39 Inches, the soil is very dark gray,
<br />neutral clay that has yeliowish brown mottles. Between
<br />depths of 39 and 57 inches, the soil is dark grayish
<br />brown, mildly alkaline Clay that has olive mottles. Be-
<br />tween depths of 57 and 66 inches, the soil is olive,
<br />moderately alkaline clay that has brownish mottles. The
<br />underlying material is light brownish gray and pale olive,
<br />moderately alkaline, stratified shaly clay to a depth of 75
<br />inches.
<br />Heiden solis are on sides of ridges. These soils are
<br />well drained and are moderately alkaline throu~hout. The
<br />surface iayer is very dark grayish brown clay about 26
<br />inches thick. Between depths of 26 and 48 inches, the
<br />soil is olive gray Clay. Between depths of 48 and 62
<br />inches, the soil is mottled dark grayish brown, light olive
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