Reconnoissance soil survey of South Texas Page: 55 of 115
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BECONNOISSANCE SOIL SURVEY OF SOUTH TEXAS. 53
material, as must be done in plowing, the entire mass, however,
becomes a loam. There is usually present a sufficient amount of
clay to make it slightly sticky when wet and to cause it to be compact
with the formation of some clods, but under proper moisture
conditions cultivation easily breaks these down and the soil gives a
friable, loamy seed bed.
The depth of the surface soil ranges from 8 to 20 inches, with an
average of. probably 12 inches. The loamy surface covering is
usuallyshallowest where the type borders the Victoria clay, the depth
to the heavier subsoil gradually decreasing until it grades into the
The color is popularly classed as black, although it is more strictly
a dark gray. It varies, however, from a grayish-brown to almost
black, depending upon the amount of humus present. Upon the
surface, especially in the depressions, there is usually a thin crust of
very light-gray material, which gives to uncultivated areas the appearance
of a much lighter colored soil. The amount of moisture present
has a very marked influence, also, upon the shade of color, fields
which were distinctly gray when dry becoming black when moistened
by recent rains. The surface is often literally strewn with white helix
shells, which contain a large amount of lime and give a lighter color
to uncultivated areas.
There is not a very sudden change in the character of material
between soil and subsoil, but rather a gradual merging into the
heavier, lighter colored subsoil. The texture of the subsoil is in
general a compact clay loam, but this varies from a loam upon the one
side to a light clay upon the other. As a rule the heavier subsoil
is found associated with the clay, while the lighter texture occurs
where the type is surrounded by areas of the fine sandy loam. Sometimes
there is present a very hard adobelike layer in the upper subsoil,
which breaks into cubes upon drying and exposure to the air.
This condition is most common in areas with the heavier subsoil, and
is very noticeable immediately around Sinton. The subsoil is of a
light to dark drab or slate color, often containing many white spots,
due to the large amount of lime present.
In the vicinity of Harlingen a somewhat different phase of this
type was encountered. The surface soil contains a rather high percentage
of sand, and in the lower subsoil a stratum of sharp gray sand
i sometimes encountered. The subsoil is also rather darker colored
than the average. This phase is limited in extent, occurring only in
a few narrow strips in the vicinity of Harlingen, Rhodes, and Combes.
Almost the entire southern area is slightly different from the development
farther north and has some of the characteristics of the Brennan
loam. This is probably due to the influence of the Rio Grande at the
time of the deposition of the material.
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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/m1/55/: accessed August 20, 2017), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting UNT Libraries Government Documents Department.