Reconnoissance soil survey of South Texas Page: 43 of 115
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RECONNOISSANCE SOIL SURVEY OF SOUTH TEXAS. 41
sand becomes sufficiently great to be shifted by the wind and forms.
small drifts around clumps of vegetation. In these sandy areas it is
not uncommon for the sand to have a slightly redder tinge than is
true of typical areas. Such areas as have just been described occur
bordering those of more sandy texture found east of San Ygnacio,
north of the La Purisima ranch, west of La Rosita ranch, and to a
less extent in several other localities. In places the surface is quite
compact, giving it somewhat the appearance of a loam, but the sand
content is always sufficiently high to render it easily tilled under a
wide range of moisture conditions.
The soil is generally high in lime content, but very low in organic
matter, and when cultivated methods of increasing the latter should
be adopted. The percentage in general increases toward the east,
due to the greater rainfall. As the amount of humus increases the
color becomes darker and the type passes into the Victoria fine
sandy loam of the level coast country. The gradation between these
types extends over a wide stretch of country, and the line of separation
on the map is entirely arbitrary, there being very little difference
in the soil for several miles on either side, although quite distinct
where the two are typically developed.
At a depth of 10 to 12 inches the soil grades into a compact, heavy,
sandy loam subsoil of a gray or grayish-brown color. When dry
this subsoil is sometimes so compact as to have the appearance of a
hard, baked clay. However, the upper subsoil contains a high percentage
of sand, and although the silt and clay content increases
with depth much sand is found throughout the entire 3-foot section.
In the heavier phases a gray loam or silty loam is encountered at a
depth of 3 to 5 feet, which is usually underlain by clay.
In various parts of the area shown as Brennan fine sandy loam in
the map, especially south of El Jaral and Abritas, southwest of
Los Cubus, on the Mira Flores, and east of La Perla ranches, are
small lakelike basins almost surrounded by more rolling country.
These areas are occupied by a clay or heavy clay loam very different
from the Brennan fine sandy loam and would have been shown separately
on a map of larger scale. The soil in these depressions is a
dark brown to reddish-brown clay loam or clay which becomes hard,
baked, and slightly sun-cracked when in a dry condition. At a
depth of 8 to 10 inches it becomes lighter in color, with but little
change in texture. These areas usually have poor drainage. The
presence of a species of "saltbush" or "salt-grass," together with
small bare spots, and the absence of a heavy growth of native vegetation
indicates that alkali has accumulated in considerable amounts.
Orgin.--The Brennan fine sandy loam has been formed from a
deposit of calcareous fine sandy loam or sandy clay of Pleistocene
age. The small rainfall has prevented the leaching out of the lime,
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Coffey, George Nelson. Reconnoissance soil survey of South Texas, book, June 16, 1910; Washington D.C.. (texashistory.unt.edu/ark:/67531/metapth19753/m1/43/: accessed December 11, 2017), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting UNT Libraries Government Documents Department.