LOCATION PLUMFIELD ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Aquic Fragiudalfs
TYPICAL PEDON: Plumfield silty clay loam - on an 8 percent slope in a grass-legume field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; yellowish brown (10YR 5/4) silty clay loam, light yellowish brown (10YR 6/4) dry; weak fine granular structure; friable; common very fine and fine roots; very strongly acid; abrupt smooth boundary. (4 to 9 inches thick)
Btx1--5 to 7 inches; yellowish brown (10YR 5/6) silty clay loam; moderate coarse prismatic structure parting to strong medium platy; very firm, brittle; few very fine roots between peds; few distinct dark yellowish brown (10YR 4/6) clay films on vertical faces of peds; common fine round iron and manganese accumulations; very strongly acid; abrupt smooth boundary. (0 to 11 inches thick)
2Btx2--7 to 12 inches; yellowish brown (10YR 5/6) silty clay loam; common fine and medium distinct grayish brown (10YR 5/2) mottles; moderate very coarse prismatic structure (5 to 8 inches in diameter); very firm, brittle; common distinct grayish brown (10YR 5/2) and brown (10YR 5/3) clay films on vertical faces of polygons; few prominent white (10YR 8/1) skeltans (silt) on faces of polygons; common fine round iron and manganese accumulations; very strongly acid; clear smooth boundary.
2Btx3--12 to 36 inches; yellowish brown (10YR 5/6) silt loam; common fine distinct grayish brown (10YR 5/2) mottles; moderate very coarse prismatic structure (6 to 9 inches in diameter); very firm, brittle; very few distinct dark yellowish brown (10YR 4/6) clay films on vertical faces of polygons; cracks between polygons filled with dark yellowish brown (10YR 4/6) silty clay loam; common fine round iron and manganese accumulations; strongly acid; 1 percent igneous pebbles; gradual smooth boundary. (The combined thickness of the 2Bxt horizon is 22 to 50 inches thick)
3Btg1--36 to 46 inches; grayish brown (10YR 5/2) silty clay loam; many fine and medium distinct yellowish brown (10YR 5/4 and 10YR 5/6) mottles; moderate medium prismatic structure parting to moderate medium angular blocky; very firm; few distinct dark yellowish brown (10YR 4/6), brown (10YR 5/3), and gray (10YR 5/1) clay films on faces of peds; common fine irregular soft iron and manganese masses; common fine irregular barite clusters; 1 percent gravel; moderately acid; gradual smooth boundary.
3Btg2--46 to 56 inches; grayish brown (10YR 5/2) silty clay loam; many fine and medium distinct yellowish brown (10YR 5/4 and 10YR 5/6) mottles; weak coarse prismatic structure; very firm; few distinct dark yellowish brown (10YR 4/6), brown (10YR 5/3), and gray (10YR 5/1) clay films on faces of peds; common fine irregular soft iron and manganese masses; common fine irregular barite clusters; 1 percent gravel; strongly acid; gradual smooth boundary.
3Btg--56 to 70 inches; grayish brown (10YR 5/2) silty clay loam; many fine and medium distinct yellowish brown (10YR 5/4 and 10YR 5/6) mottles; weak coarse prismatic structure; very firm; common faint gray (10YR 5/1) and brown (10YR 5/3) clay films on faces of peds; many fine irregular soft iron and manganese masses; common fine irregular barite clusters; 1 percent gravel; moderately acid.
TYPE LOCATION: Franklin County, Illinois; about 500 feet east and 2.060 feet south of the northwest corner of sec. 18, T. 7 S., R. 2 E.
RANGE IN CHARACTERISTICS: The depth to the top of the fragipan is 5 to 20 inches. The depth to the base of soil development is greater than 60 inches (see REMARKS).
The Ap horizon has value of 4 or 5 (5 or 6) dry, and chroma of 2 or 3. It is silty clay loam or silt loam. Average clay content ranges from 20 to 30 percent and average sand content ranges from 5 to 15 percent. Reaction ranges from very strongly acid to neutral.
The Btx horizon (that formed in Peoria loess and to a depth of less than 20 inches ) has value of 4 to 6 and chroma of 2 to 8. It is silty clay loam or silt loam. Average clay content ranges from 20 to 30 percent and average sand content ranges from 5 to 15 percent. Macro structure is coarse or is very coarse prismatic in less than 60 percent of its volume. Reaction ranges from very strongly acid to moderately acid.
The 2Btx horizon has value of 4 to 6 and chroma of 2 to 8. It is silt loam, loam, or silty clay loam. Average clay content ranges from 20 to 30 percent and average sand content ranges from 10 to 30 percent. Coarse fragment content is less than 3 percent. Structure is very coarse prismatic in 60 to 90 percent of its volume. Macro peds are coated with albic material in at least the upper 6 inches. Reaction ranges from extremely acid to strongly acid.
The lower part of the control section (3Btg or 2Btg horizon) has hue of 10YR or 7.5YR, value of 4 to 6, and chroma of 2 to 6. It is loam, silt loam, clay loam, or silty clay loam. Average clay content ranges from 20 to 35 percent, average sand content ranges from 15 to 40 percent, and average coarse fragment content ranges from 1 to 10 percent. Reaction ranges from extremely acid to moderately acid.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Plumfield soils are on actively degrading positions on side slopes. They formed in less than 20 inches of Peorian loess (sand content less than about 8 percent); in 20 to 50 inches of Roxana silts and/or pedisediment (sand content 10 to 30 percent); and in weathered Illionian glacial till to depths greater than 60 inches. Slopes range from 5 to 18 percent. Mean annual air temperature ranges from 54 to 57 degrees F, mean annual precipitation ranges from 42 to 48 inches, frost free days range from 180 to 210, and elevation ranges from 500 feet to 750 feet above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Atlas, Ava, Blair, and Hickory soils. Atlas, Blair, and Hickory soils do not have fragipans. Atlas and Hickory soils are stratigraphically lower than Plumfield soils. Ava soils are on shoulders and crests above the Plumfield soils.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium or rapid. Permeability is very slow.
USE AND VEGETATION: Most areas are cultivated. Corn, grain sorghum, soybeans, and wheat are commonly grown. Some areas are used for forage production. Native vegetation is oak-hickory forest.
DISTRIBUTION AND EXTENT: Southern Illinois. The extent is small.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED (proposed): Franklin County, Illinois, 1992.
REMARKS: Plumfield soils were previously mapped as severely eroded soils that were taxadjunct to the Ava series because they lacked an argillic horizon above the fragipan. Horizon designations become difficult to discuss in the RANGE IN CHARACTERISTICS section because of different possibilities of parent materials. Although not required as part of the series concept, most pedons described so far have a thin mantle of Peoria loess as the upper stratigraphic unit. The next stratigraphic unit (horizon designation prefix 2 in this pedon) is Roxana silt or pedisediment. This material has its lower boundary at the contact with glacial till (presumably of Illinoian age). In most places the glacial till has evidence of prior soil development, the Sangamon soil. Many of the properties of this horizon (horizon designation prefix 3 in this pedon) are inherited from the paleosol. It is believed, however, that present pedogenic processes have resulted in some properties of the Plumfield soils being super-imposed on these horizons.
Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - the zone from the surface to a depth of 5 inches (Ap horizons); fragipan - the zone from 7 to 36 inches (2Btx2 and 2Btx3 horizons).