LOCATION TILLOU LAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, thermic Aquic Glossudalfs
TYPICAL PEDON: Tillou silt loam, level ridge crest less than 1 percent slope in pine woodland.
(Colors are for moist soil unless otherwise
stated).
A1--0 to 5 inches; dark grayish brown (10YR 4/2) silt loam;
weak medium subangular blocky and weak fine granular structure; friable; common fine and medium roots; strongly acid; clear smooth boundary. (3 to 7 inches thick).
A2--5 to 8 inches; brown (10YR 5/3) silt loam; common medium distinct dark grayish brown (10YR 4/2) mottles; weak coarse subangular blocky structure; friable; common fine and very fine roots; common fine black iron-manganese concretions; very strongly acid; clear wavy boundary. (2 to 4 inches thick).
B21t--8 to 15 inches; yellowish brown (10YR 5/4) silt loam; common medium faint dark brown (10YR 4/3) and few medium faint
light brownish gray (10YR 6/2) mottles; weak medium subangular
blocky structure; friable; few fine roots; few fine pores; thin patchy clay films on faces of peds; common fine black
iron-manganese concretions; very strongly acid; clear wavy
boundary. (5 to 12 inches thick).
B&A--15 to 20 inches; yellowish brown (10YR 5/4) silt loam
(60% B2t); light brownish gray (10YR 6/2) silt loam (40% A2);
common medium distinct dark yellowish brown (10YR 4/4) and common coarse distinct light brownish gray (10YR 6/2) mottles; weak
medium subangular blocky structure; friable; few medium roots; few fine pores; common fine black iron-maganese concretions; few black streaks; few brittle bodies; A2 material between peds and interspersed within peds; very strongly acid; gradual wavy
boundary. (5 to 15 inches thick).
A&B--20 to 30 inches; light gray (10YR 7/2) silt loam (60%
A2) and yellowish brown (10YR 5/4) silt loam (40% B2t); weak
medium subangular blocky structure; friable; few fine roots;
common fine pores; few fine black and brown iron-manganese concretions; about 20% brittle bodies that are up to 2 inches in diameter; tongues of this horizon extend to a depth of 40 inches; strongly acid; abrupt irregular boundary. (5 to 15 inches thick).
B'22t--30 to 40 inches; yellowish brown (10YR 5/4) silty clay loam; 10% light brownish gray (10YR 6/2) silt coatings and
streaks; weak medium subangular blocky structure; plastic and
sticky; many fine pores inside of peds; thin patchy clay films; common black and brown concretions that are up to 3 centimeters in diameter; about 20% firm brittle bodies that are up to 5
centimeters in diameter; ped interiors interspersed with silt; strongly acid; abrupt irregular boundary. (6 to 16 inches thick).
B'23t--40 to 48 inches; brownish yellow (10YR 6/6) and light yellowish brown (10YR 6/4) silty clay loam; moderate medium and coarse subangular blocky structure; firm; few fine roots; common
very fine pores; thin patchy clay films on peds and in pores; few fine and medium black and brown concretions; few thin silt coats
on peds; strongly acid; gradual wavy boundary. (5 to 16 inches thick).
IIB'24t--48 to 66 inches; light yellowish brown (10YR 6/4)
silt loam; weak very coarse subangular blocky structure; hard,
very firm, slightly brittle; few fine roots between peds; common
very fine pores in peds; thick continuous clay films on vertical faces of peds, thin continuous clay films on horizontal faces of peds; common very fine black stains on faces of peds; few fine and medium brown concretions; few medium pale brown (10YR 6/3) silt pockets; slightly acid; gradual wavy boundary. (0 to 20 inches thick).
IIB'25t--66 to 76 inches; yellowish brown (10YR 5/4) silt
loam; common medium faint dark yellowish brown (10YR 4/4) and
light brownish gray (10YR 6/2) mottles; weak coarse and very
coarse subangular blocky structure; few fine roots; many fine
pores; few discontinuous clay films; few fine black concretions;
few black stains; neutral.
TYPE LOCATION: Morehouse Parish, Louisiana; about 16 miles
northeast of Bastrop in the SW1/4NE1/4, sec. 9, T. 23 N., R. 7 E.
RANGE IN CHARACTERISTICS: Depth to the loamy Southern Coastal
Plain sediment ranges from 40 to 80 inches. Solum thickness
ranges from about 60 to over 100 inches. The reaction of the A,
B&A, and B21t horizons ranges from medium acid to very strongly
acid, except for surface layers where limed. The reaction of the B22t and lower horizons ranges from strongly acid to mildly
alkaline. The effective CEC of the control section is 50 percent
or more saturated with exchangeable aluminum to a depth of 30
inches or more.
The A horizons have hue of 10YR, value of 3 to 5, and chroma of 2
or 4.
The B2t horizon has hue of 10YR, value of 4 to 6, and chroma of 4
to 6. Mottles are in shades of gray, yellow, and brown. Texture
is silt loam or silty clay loam.
The B&A and A&B horizons have B parts with the same color and
texture range as the above B2t horizon. The A part has hue of
10YR, value of 5 to 7, and chroma of 1 to 3.
The B'2t horizons have hue of 10YR, value of 4 to 6, and chroma of
4 to 6. Mottles are in shades of gray, brown, or red. Texture is silt loam or silty clay loam.
COMPETING SERIES: These are the
Egypt and
Fred series of the same family and the
Calloway,
Duralde,
Frizzell,
Metcalf,
Necessity,
and
Pooleville series is similar families. Egypt soils lack Bt horizon above the B&A horizon. Fred soils have alkaline B
horizons. Calloway and Necessity soils have fragipans. Duralde
and Pooleville soils lack Bt horizons and have siliceous sand mineralogy. Frizzell soils have coarse silty control sections. Metcalf soils have clay lower B horizons.
GEOGRAPHIC SETTING: Tillou soils are on level to gently sloping terraces. Slope gradients range from 0 to 5 percent. The soil formed in a mantle of loess over Southern Coastal Plain sediments. The climate is warm and humid. The mean annual precipitation is about 50 inches and the mean annual temperature is about 66
degrees F near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the
Guyton and
Providence series as well as the competing
Frizzell series.
Guyton soils, on concave parts of the landscape and along drainageways, are poorly drained. Providence soils, at slightly higher elevations, are better drained and have a fragipan.
DRAINAGE AND PERMEABILITY: Tillou soils are somewhat poorly
drained; runoff is slow and permeability is slow. An apparent
water table is at a depth of 0.5 to 2.5 feet during late winter
and early spring.
DISTRIBUTION AND EXTENT: Louisiana and possibly Arkansas. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Morehouse Parish, Louisiana; 1981.
REMARKS: Tillou soils were formerly included with the Calloway series in mapping. In addition to lacking a fragipan they differ from the Calloway series by having significantly lower yields for most commonly grown crops. This is due to high levels of exchangeable aluminum in the control section.