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Issued December 29, 1911.

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF SOILS— CIRCULAR No. 49.
MILTON WHITNEY, Chief of Bureau.

SOILS OF THE EASTERN UNITED STATES AND THEIR USE— XXVI.

THE HOUSTON CLAY.

JAY A. BONSTEEL,

Scientist in Soil Survey.

WASHINGTON":

GOVERNMENT PRINTING OFFICE.

1911.

BUREAU OF SOILS.

Milton Whitney, Chief of Bureau.
Albert G. Rice, Chief Clerk.

SCIENTIFIC STAFF.

Trank K. Cameron, in charge of Physical and Chemical Investigations.
Curtis F. Marbut, in charge of Soil Survey.
Oswald Schreiner, in charge of Fertility Investigations.
2

SOILS OF THE EASTERN UNITED STATES AND THEIR USE— XXVI.

THE HOUSTON CLAY.

GEOGRAPHICAL DISTRIBUTION.

The Houston clay is an important and extensively developed soil
type of the Cretaceous prairie region of the Gulf Coastal Plain. It
has been encountered in 21 areas located in 4 States and mapped
to an aggregate extent of 763,688 acres by the Bureau of Soils. The
most extensive occurrences are in central and western Alabama,
northeastern Mississippi, and west central Texas. In all of these
areas it is associated with the black prairie soils.

CHARACTERISTICS OF SOIL AND SUBSOIL.

The surface soil of the Houston clay is prevalently a brown or
black loamy clay ranging in depth from 4 to 10 inches underlain by
a stiff, plastic, light-brown, yellow, or gray clay, which at an average
depth of about 20 inches passes into a light-gray or white rotten
limestone or chalk. The color of the surface soil is somewhat varied,
depending upon its topographic position, the darker colored areas
occurring in more level situations and in slight depressions, while
the light-colored brown or gray surface soils are found upon steeper
slopes where erosion has largely removed the surface soil material.
The Houston clay is a residual soil derived from the weathering of
the Selma chalk in central Alabama and northeastern Mississippi;
of the "rotten limestone" of the Jackson stage of the Eocene in
the south central counties of Mississippi; and from the Austin chalk
in west central Texas. In all cases these formations consist of
impure argillaceous limestones or marls of Eocene or Cretaceous
age exposed in broad belts along the outcrops of the formation^.
Within each of the areas where these formations and their derivative
soils occur there are also areas of varying size where more recent
deposits have been laid down over the marls. In consequence
there has been more or less mingling of material from other sources
with that derived directly from the underlying marl, which has given
rise to some variation in the composition and coloration of the type,
particularly the surface soil. The brown or reddish-brown surface

15985""— Clr. 49-H 3

4 SOILS OF THE EASTERN UNITED STATES.

soils overlying the plastic clay and the marl at greater depths are
sometimes thin remnants of these latter formations.

The Houston clay, together with other members of the Houston
series, is easily distinguished from all other soil types of the Coastal
Plain region through its derivation from the underlying marls, the
existence of a white or gray chalky material at depths ranging from
^ 20 inches to 3 or 4 feet, the existence of calcareous nodules and
fragments of shell in both soil and subsoil, and the prevalent brown,
drab or black color of the surface soil itself. It can not be confused
with the other dark-colored soils of the region, since these are prev-
alently alluvial, while the Houston clay occurs only upon the upland
prairies.

SURFACE FEATURES AND DRAINAGE.

The greater portion of the Houston clay possesses a level to gently
rolling surface. Large tracts are almost absolutely level or broken
by low ridges from 15 to 30 feet above the general level of the country.

The surface of the Houston clay lies at elevations ranging from
about 125 feet to 500 or 600 feet above sea level. In general the
• type is fairly well drained, so far as surface run-off is concerned. In
fact, erosion occurs over extensive areas of its surface. The inter-
nal and subsoil drainage of the type, owing to its stiff, waxy nature,
is not particularly good, although the tendency toward granulation
in the surface soil somewhat assists in this respect.

LIMITATIONS IN USE.

The Houston clay is one of the more plastic clay soils of the upland
portion of the Gulf Coastal Plain. In common with other soils of
similar texture it is not so well suited to the production of special
crops as to the growing of the great staples, including corn, cotton,
oats, and hay. In fact very few vegetables, fruits, or other special
crops may be grown to advantage upon the type because of its stiff,
plastic nature, the large amount of moisture which is retained under
normal conditions of rainfall and the difficulty of maintaining perfect
tillage during the growing season. The same characteristics which
prevent its general use for special crops render it particularly favor-
able to the production of the staples.

The Houston clay is a highly calcareous soU. Numerous analyses
of the lime content of the subsoil have shown it to contain from 2^
to 35 per cent of calcium carbonate, while the percentage of lime in
the gray chalky material at greater depths is even higher than this.
In consequence, wherever drainage conditions are at aU favorable,
this type constitutes one of the best alfalfa soils to be found in the
upland portion of the Gulf States. It also produces other leguminous

THE HOUSTON CLAY. 5

crops to good advantage, and its continued fertility under constant
one-crop farming is a notable feature of the type.

A considerable proportion of the total acreage of the Houston clay
can not be occupied for general farming operations. The level,
rolling, and gently sloping areas of the type, where the surface soil
extends to a depth of 6 inches or more, are well suited to general
farming, but within many fields and universally along the margins
of the type, erosion has proceeded so rapidly that the surface soil
can not be maintained under the ordinary conditions of clean culti-
vation for cotton and corn, and many ''galled" areas, numerous
gullies, and other evidences of excessive erosion indicate less valuable
soil areas than the normal for the type. Upon such eroded areas
little moisture is absorbed during the periods of rain, and the surface
soil is bodily removed with every heavy shower. In consequence,
crop yields on such areas are small, even when any stand can be
secured at all. Land of this character should be seeded down to the
grasses, using alfalfa where it is possible to obtain a stand, and per-
mitting Johnson or Bermuda grass, or even Melilotus to cover the
ground where erosion has proceeded to such an extent that it is not
practicable to seed down to alfalfa.

The Houston clay occurs under a considerable range of rainfall
conditions. In Alabama, Mississippi, northern Louisiana, and north-
eastern Texas the precipitation is abundant for the production of
the ordinary staple crops, but in west central Texas there are areas
of the type which occur under semiarid conditions and in these
localities periods of drought late in the summer frequently interfere
with the production of either cotton or corn. In such localities large
areas of the type are permitted to grow up to wild prairie grasses,
which are either grazed off or cut for hay.

There is thus considerable variation in the character of the agri-
culture which is conducted upon the Houston clay.

IMPROVEMENT IN SOIL EFFICIENCY.

There are two almost equally important improvements in soil
efficiency which may be effected in connection with the tillage of the
Houston clay. The first of these is the prevention of excessive ,
erosion, already indicated. Wlierever the surface slopes within this
type exceed 10 degrees of declivity it is practically impossible to
maintain the land under cultivation. With the adoption of contour
farming and of terracing, together with deep plowing, even the
steeper slopes may be tilled to advantage, but in general it would be
bettor to secure a stand of alfalfa, or, if this proves to be impossible,
to allow Johnson grass, Bermuda grass, or Melilotus to grow upon
such slopes, to be cut either as hay or to be grazed off by the work

■6 SOILS OF THE EASTERN UNITED STATES.

stock, dairy, and beef animals of the plantation. Upon the gentler
slopes deeper plowing, the careful rotation of crops, and an effort to
maintain a winter cover crop to protect the surface soU during periods
of heaviest precipitation wUl prevent excessive erosion and maintain
the surface soU in its proper place.

Under the older methods of tillage, where cotton was raised con-
secutively for a long period of time, or at the most was only alternated
with com at infrequent periods, the surface drainage of the Houston
clay was adequately maintained by plowing the land in ridges and
permitting the excess water to flow off through the water furrows.
While this promoted erosion upon all of the steeper slopes, upon the
more gentle slopes it was adequate for the fairly effective drainage of
the type. Within more recent years improved farming methods
have been introduced, which require the rotation of cotton, com,
and some forage grass, particularly alfalfa. This improved method
of farming tends to prevent the use. of the ridge and furrow method
of surface cultivation. It is rapidly bringing about the broadcast
plowing of the type even when the fields are ridged later with an
approach to the old water furrow method of cultivation. Then, too,
the maintenance of portions of the type for several years at a time in
alfalfa has necessitated greater attention to surface and subsoil
drainage. It is only upon the better drained portions of the type
that alfalfa is uniformly successful, and if the production of this crop
is to be extended upon the Houston clay the installation of tile
drains upon certain portions of the type will be necessary. Wliile
the subsoil to a depth of about 2 feet is waxy and plastic, still there
is a constant tendency under proper methods of tillage toward granu-
lation in the surface soil and immediate subsoil. Fields may be
effectively tile drained, provided the tile are laid at a depth not less
than 2 feet below the surface, and strung at intervals of approxi-
mately 40 feet. In the majority of cases the results will not be
immediately evident, but increasing improvement will be noted from
year to year. Attempts along this line have been made so recently
that very little may be stated positively in regard to the outcome,
although soils seemingly as plastic and impervious in the prairie
regions of the North Central States have been effectively under-
drained in this manner.

In addition to these two methods of improving the Houston clay
it is essential that rotation of crops should be practiced upon tliis soil.
A reasonably well-founded behef in the wonderful fertihty of the type
has led to its almost constant cultivation to one or at most two crops —
cotton and corn. In certain instantes in the eastern Gulf States,
cotton has been raised continuously for 25 years upon this soil,
maintaining an average yield of one-half bale to the acre or better,

THE HOUSTON CLAY. 7

in spite of seasonal variations due to climatic conditions. It is
believed, however, that this constant cultivation of a single crop has
materially reduced the yields over a considerable portion of the type.
This in part is probably due to the promotion of excessive erosion
and partly to unfavorable physical conditions induced by unvaried
cultivation. In contrast, upon limited areas wheriB a crop rotation
has been adopted, yields of three-fourths of a bale to one bale of
cotton per acre are easily obtained. The general adoption of suitable
rotations throughout the area occupied by the Houston clay is there-
fore desirable.

LIMITATIONS UPON SPECIAL CROPS.

Because of its characteristic texture, the Houston clay is not well
suited to the production of any special crops. Moreover, it is usually
associated with soils in every area which are weU suited to the pro-
duction of special crops, and it is, therefore, not advisable to attempt
the production of any but the staple crops, including cotton, com,
oats, and hay, upon this type.

EXTENT OF OCCUPATION.

In the majority of the more eastern areas where the Houston clay is
found, from 60 to 80 per cent of the type is occupied agriculturally.
Probably one-half of the total area of the type thus far mapped is
annually cropped. An additional one-fourth is used for pasturage
purposes. The remaining 25 per cent, consisting chiefly of steep
slopes and isolated patches of smaU size, remains unoccupied. Upon
such areas a small amount of timber, principally cedar, is to be found.
In the more western areas, under semiarid conditions not more than
10 to 15 per cent of the type is annually tilled, and the remainder
supports wild grasses, which are cut for hay or grazed off. Wherever
the type is found under suitable climatic conditions, it is considered
desirable for farming purposes, and while there is a wide range in the
selling price of different areas, dependent largely upon the surface
configuration of the type and its location with regard to transporta-
tion facihties, yet aU areas which are reasonably level and fairly
near to railroad transportation are highly esteemed. Tracts so situ-
ated command prices ranging from $30 to $75 per acre.

CROP ADAPTATIONS.

The Houston clay is one of the important Upland cotton soils of
the Gulf region. Portions of the type have produced cotton almost
continuously for periods ranging from 25 to 75 years, maintaining a
high average yield during the entire time. In spite of a tendency

8 SOILS OF THE EASTERN UNITED STATES.

toward droughty conditions during the latter part of the growing
season it may be stated that the average cotton yield upon the
Houston clay is undoubtedly in excess of one-half bale per acre.
There are, of course, seasonal variations, dependent chiefly upon
rainfall conditions, but in general the type produces from one-third
bale as a minimum crop, to yields in excess of 1 bale per acre upon
well-situated land which has been properly tilled. This soil is so
highly esteemed for the production of cotton that in many areas this
crop is planted almost to the total exclusion of any other.

Corn yields range from 30 to 50 bushels per acre, with maximum
yields as high as 75 bushels. Under unfavorable conditions the pro-
duction drops as low as 8 to 12 bushels per acre. The lower yields
prevail over areas subjected to excessive erosion or areas water-
logged by excessive rainfall which has prevented the germination or
subsequent growth of the corn crop during the earlier part of the
season or where excessive drought in midsummer has cut down the
grain yield.

Over considerable areas of the Houston clay Johnson grass, aUied
to the sorghums, has attained a foothold practically to the exclusion
of cotton or corn. Johnson grass is considered one of the pests of the
cotton planter, yet it yields from 1^ to 3 tons of hay per acre, worth
from $15 to $18 per ton. Bermuda grass has so invaded some of the
fields that they have been given up to it, being used for grazing or for
the cutting of hay.

More recently alfalfa has been introduced upon the Houston clay
and, particularly in Alabama and Mississippi, growing this crop has
become a special feature of the agriculture of areas occupied by the
type. The Houston clay possesses several characteristics requisite
for successful alfalfa growing. In the first place it is decidedly cal-
careous, thus favoring the inoculation of the alfalfa and the mainte-
nance of the requisite bacteria within the root nodules. When prop-
erly treated the surface soil of the Houston cla}' is also granular,
friable, and easily maintained in good tilth. Consequently an even
stand of alfalfa may be obtained. The crop is only suited to those
portions of the type which are either naturally well drained or over
which some effort has been made at the artificial underdrainage of the
subsoil. Alfalfa is a deep-rooted plant, which is decidedly intolerant
of a saturated condition of the subsoil. In consequence, extremely
level areas of the Houston clay, where water stands either at the sur-
face or within the subsoil, are not suited to the production of this crop.
There are, however, thousands of acres of the type sufficiently well
drained to constitute an admirable soil for alfalfa growing. Where
a stand of the crop has been obtained it is possible, with the long
growing season of the Gulf coast region, to obtain four and frequently

THE HOUSTOI^r CLAY. 9

five cuttings annually, averaging about 1 ton of hay to the cutting.
Some difficulty is experienced in curing the first crop, since it is ready
for harvest during the rainy portion of the spring months, but the
subsequent crops are matured at seasons which are usually favorable
for the drying out of the hay.

The Houston clay and its related type, the Houston black clay, are
undoubtedly the best alfalfa soils of the "black prairie" regions in
Alabama and Mssissippi, while these types are coming to be so recog-
nized in the more western occurrences in Texas. Since the region
is one which to the present time has not produced a sufficient amount
of forage for the sustenance of the work stock, good hay, like that
made from alfalfa, is always in demand, at prices ranging from $15
to $20 per ton. In consequence an acre well seeded to alfalfa con-
stitutes a more certain and usually a more valuable acre than the same
area planted either to cotton or com. Considering the smaller
amount of hand labor requisite for tending and harvesting the alfalfa
crop, it is evident that the profits from alfalfa growing equal or
exceed those to be derived from cotton culture, even when yields of
the latter exceed one-half bale per acre.

Winter oats are also grown to some extent upon the various areas
of the Houston clay. The yields when the grain is cut for thrashing
range from 25 to 35 bushels per acre. The oats are usually cut as
a forage crop.

In northeastern Texas some winter wheat is also grown upon the
Houston clay, giving yields of 8 to 15 bushels per acre. The crop
is unusual.

FARM EQUIPMENT.

The Houston clay ordinarily occurs in association with other types
of soil, and the normal farm equipment of buildings, machinery, and
stock does not differ materially from that of the average cotton
plantation. In fact a considerable amount of difficulty in the man-
agement of this type has been experienced through the continued
attempt to till it by means of the one-horse or one-mule hitch, which
is adequate for the plowing and cultivation of the more sandy soils
prevalent through the Gulf States. The stiff, waxy nature of the
Houston clay does not lend itself to this treatment. In the more
progressive communities there is an increasing tendency toward the
use of the two or four mule hitch and of the disk plow and disk
harrow in the preparation of this land. It is not possible to procure
a properly granulated and thoroughly mellow seed bed with the
ordinary light-weight equipment used most commonly upon cotton
plantations. Heavier teams and better tools are required to bring
the Houston clay to its full degree of productivity.

y^ SOILS OF THE EASTERN UNITED STATES.

SUMMARY.

The Houston clay is an important Upland cotton soil of the "black
prairie" regions of Alabama, Mississippi, and Texas.

The surface soU to a variable depth is a brown or black granular
clay loam or clay. This is underlain by a lighter brown or yellow
plastic clay subsoil to an average depth of about 20 inches, where
the gray or whitish chalk or rotten limestone is usually encountered.
It occupies level to rolling prairie areas, frequently bordered by
steeply sloping and eroded sections along the stream courses.

The drainage of the type is usually fairly well established, although
upon the more level areas the internal draiuage of the subsoil may
be defective.

Erosion is one of the principal difficulties experienced in the occu-
pation of this land, and slopes iu excess of 10° should be covered
with grass for pasturage purposes.

Tile underdrainage should be installed upon the more level areas,
especially if alfalfa is to be grown.

The Houston clay is in no sense a special crop soil, but is con-
sidered one of the best Upland cotton soUs. It is also fairly well
suited to the production of com and is coming to be especially
esteemed for the growing of alfalfa.

In general the greater portion of the different areas of the Houston
clay is occupied for agricultural purposes. The more eroded areas
and those remote from lines of transportation are less completely
occupied, while in the semiarid portions of southwestern Texas the
grazing of the wild grasses constitutes the chief use of the type.

The proper tillage of the Houston clay requires heavier farm teams
and improved machinery.

Approved.

James Wilson,

Secretary of Agriculture .

Washington, D. C, October 30, 1911,

■oaq lO'^.

APPENDIX,

The following table shows the extent of the Houston clay in the areas surveyed
to this time.

In the first column ia stated the particular soil survey in which the soil was encoun-
tered; in the second column its extent of development in acres; and in the third
column the volume of the Field Operations of the Bureau of Soils in which the report
upon the area may be found. Those desiring a detailed description of the soil and of
the general conditions which surround it in any particular area may consult these
volumes in almost any public library.

Areas of Houston clay encountered in the soil survey.

Alabama:

Autauga County

Butler County

Dallas County

Hale County

Macon County 2

Montgomery County.

Perry County

Sumter County

Louisiana;

Winn Parish

Mississippi:

Clay County

Jasper County

Monroe County

Oktibbeha County . . .

Pontotoc County

Prentiss County

Texas:

Austin area'

Franklin County

Grayson County

San Antonio area ^ . . .

San Marcos area

Waco area

Survey.

1 Year of publication, Field Operations.
« Mapped as Houston black clay.
» Mapped as Austin clay.

Area of soil.

Date.1

Acres.

1,664

1908

10,880

1907

149,184

1905

55,104

1909

8,576

1904

86,400

1905

136,128

1902

69,048

1904

1,728

1907

28,608

1909

11,392

1907

68,176

1908

10,368

1907

11,008

1906

5,632

1907

61,440

1904

832

1908

44,096

1909

4,480

1904

6,080

1906

12,864

1905

o

11

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