Decatur Series

\<@32\>The Decatur series consists of very deep, well drained,
moderately permeable soils that formed in residuum derived from
limestone. These soils are on level to strongly sloping uplands in
valleys. Slopes are dominantly 1 to 10 percent but range from 1 to 25
percent. Near the type location, the mean annual temperature is 62
degrees F and the mean annual precipitation is more than 49 inches.
These soils are fine, kaolinitic, thermic Rhodic Paleudults.

\<@32\>Typical pedon of Decatur silt loam, 2 to 6 percent slopes, in a
cultivated area in Limestone County, Alabama; 0.5 mile west of the
crossroads at Greenbrier and 200 feet north of the paved county road;
SW1/4SW1/4 sec. 21, T. 4 S., R. 3 W.

\<@23\>Ap---0 to 7 inches; dark reddish brown (5YR 3/2) silt loam, dark
reddish gray (5YR 4/2) dry; moderate fine granular structure; friable;
few red-coated spherical fragments of chert; few fine roots; moderately
acid; gradual wavy boundary. (3 to 9 inches thick)

\<@33\>Bt1---7 to 12 inches; dark reddish brown (2.5YR 3/4) silty clay
loam, dark reddish brown (2.5YR 3/4) dry; moderate medium and fine
subangular blocky structure parting to very fine blocky; friable; thin
patchy clay films on faces of most medium-sized peds; few soft dark
concretions; few fine weathered fragments of chert; moderately acid;
gradual wavy boundary.

\<@33\>Bt2---12 to 20 inches; dark reddish brown (2.5YR 3/4) silty clay
loam, dark red (2.5YR 3/6) when crushed, less than 1/2 unit of value
higher when dry; moderate very coarse subangular blocky structure
parting to strong very fine blocky; firm; thin continuous dusky red (10R
3/3) clay films on faces of most peds; common fine pores lined with
clay; few small soft dark concretions; few fine fragments of chert; very
strongly acid; diffuse wavy boundary.

\<@33\>Bt3---20 to 45 inches; dusky red (10R 3/4) clay, dark red (10R
3/6) when crushed, less than 1/2 unit of value higher when dry; moderate
very coarse subangular blocky structure parting to strong very fine
blocky; firm, sticky and plastic; thin continuous dusky red (10R 3/3)
clay films on faces of most peds; few small dark concretions; few fine
fragments of chert; very strongly acid; diffuse wavy boundary.

\<@33\>Bt4---45 to 72 inches; dusky red (10R 3/4) clay, dark red (10R
3/6) when crushed, less than 1/2 unit of value higher when dry; moderate
very coarse subangular blocky structure parting to strong very fine
blocky; firm, sticky and plastic; thin continuous dusky red (10R 3/3)
clay films on faces of most peds; common small dark concretions; few
fine fragments of chert; very strongly acid; diffuse wavy boundary.

\<@33\>Bt5---72 to 120 inches; dusky red (10R 3/4) clay, dark red (10R
3/6) when crushed, less than 1/2 unit of value higher when dry; moderate
very fine blocky structure; firm, sticky and plastic; thin patchy dusky
red (10R 3/3) clay films on faces of most peds; few small manganese
concretions; few fragments of chert; very strongly acid. (The combined
thickness of the Bt horizons is more than 60 inches.)

\<@8\>The solum is more than 72 inches thick. The upper 50 inches of the
soil contains less than 10 percent weatherable minerals in the 20- to
200-micron size. The solum ranges from moderately acid to very strongly
acid. Any horizon may contain up to 10 percent fragments of chert and
quartzite pebbles 2 millimeters to 3 inches in size and up to 3 percent
fragments over 3 inches. Each horizon has few to many dark brown to
black concretions. In some pedons, cherty limestone bedrock is at a
depth of more than 6 feet.

\<@32\>The Ap horizon has hue of 5YR or 2.5YR, value of 2 or 3, and
chroma of 2 to 4. It is loam, silt loam, or silty clay loam. In severely
eroded areas, it is silty clay or clay.

\<@32\>The BA or AB horizon, where present, is less than 6 inches thick
and has the same range in hue, value, chroma, and texture as the A
horizon.

\<@32\>The Bt horizon has hue of 2.5YR or 10R, value of 3, and chroma of
4 to 6. The color value of the dry soil is less than 1 unit higher than
that of the moist soil. The texture in the upper 20 inches of the
horizon is silty clay loam, silty clay, or clay that contains 35 to 60
percent clay and less than 20 percent sand. The lower part of the Bt
horizon commonly contains 45 to 60 percent clay; however, the range
includes clay loam below a depth of 60 inches. Structure is usually
moderate but ranges from weak to strong and from subangular blocky to
blocky.