Established Series


The Dwight series consists of deep, moderately well drained, very slowly permeable soils that formed in clayey sediments. These soils are on uplands. Mean annual temperature is 55 degrees F, and the mean annual precipitation is 33 inches.

TAXONOMIC CLASS: Fine, smectitic, mesic Typic Natrustolls

TYPICAL PEDON: Dwight silt loam - on a 1 percent slope under native grass. (Colors are for dry soil unless otherwise stated.)

A1--0 to 5 inches; dark gray (10YR 4/1) silt loam, very dark gray (10YR 3/1) moist; weak platy structure in upper inch, weak fine granular structure below; slightly hard, friable; abundant fine roots; slightly acid; abrupt smooth boundary. (2 to 7 inches thick)

B21t--5 to 17 inches; dark grayish brown (10YR 4/2) clay, very dark brown (10YR 2/2) moist; moderate medium columnar structure parting to weak, fine, blocky; extremely hard, extremely firm; common, flattened fine roots are concentrated along surfaces of peds; few open pores; slightly acid; clear smooth boundary.

B22t--17 to 22 inches; grayish brown (10YR 5/2) clay, very dark grayish brown (10YR 3/2) moist; moderate, medium, and coarse blocky structure; extremely hard, very firm; mildly alkaline; gradual smooth boundary. (Combined thickness of B2 is 11 to 40 inches.)

B3--22 to 35 inches; brown (10YR 5/3) silty clay, dark brown (10YR 4/3) moist; common fine and medium distinct reddish yellow (7.5YR 6/6) and light gray (10YR 7/2) mottles; moderate, fine, and medium blocky structure; very hard, very firm; few fine soft accumulations of carbonates in lower part; mildly alkaline; gradual smooth boundary. (10 to 25 inches thick)

C--35 to 54 inches; pale brown (10YR 6/3) silty clay, brown (10YR 5/3) moist; common, fine and medium distinct strong brown (7.5YR 5/6) mottles in upper part, and light yellowish brown (10YR 6/4) and light brownish gray (10YR 6/2) mottles in lower part; massive; very hard, very firm; mildly alkaline; abrupt smooth boundary. (0 to 25 inches thick)

IIR--54 inches; hard cherty limestone bedrock.

TYPE LOCATION: Geary County, Kansas; 3 miles south and 1 1/2 miles east of junction of Kansas Highway 177 and Interstate 70; 650 feet north and 2,340 feet west of the southeast corner of sec. 10, T. 12 S., R. 8 E.

RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 30 to 55 inches. The mollic epipedon is 14 to 32 inches thick. Limestone bedrock commonly is at depths of 40 to 60 inches but is below 60 inches in a few pedons. Also, a few pedons have shale between the solum and limestone bedrock. Free carbonates in forms of concretions or soft masses are below 15 inches.

The A horizon has hue of 10YR, value of 4 or 5 and 2 or 3 moist, and chroma of 1 or 2. Gray silt coatings are on faces of peds in the lower 1 or 2 inches of this horizon in some pedons. This horizon is silt loam or silty clay loam. It ranges from medium acid to neutral.

The B2 horizon has hue of 10YR, 7.5YR, or 5YR, value of 3 to 5 and 2 to 4 moist, and chroma of 1 to 3. It is clay or silty clay with 45 to 60 percent clay. It ranges from slightly acid to moderately alkaline. This horizon, especially in the upper part, has columnar or prismatic structure and parts to blocky. The percent exchangeable sodium typically ranges from 5 to 10 percent in the upper part. In the lower part and in the B3 and C horizons, it ranges from 15 to 25 percent.

The C horizon has hue of 10YR, 7.5YR, or 5YR, value of 4 to 6 and 3 to 5 moist, and chroma of 3 or 4. It is silty clay or silty clay loam. It ranges from neutral to moderately alkaline. Common, fine and medium, high and low chroma, mottles are in many pedons.

COMPETING SERIES: These are the Beckton, Cavo, Degrey, Dudley, Farmsworth, Mosher, and Wood River series in the same family and the Irwin, Labette, Ladysmith, and Mento series. Beckton, Cavo, Degrey, Dudley, and Farmsworth soils have annual temperatures less than 50 degrees F. In addition, Cavo and Dudley soils contain more sand; Degrey soils have a contrasting IIC horizon of glacial till; and Farmsworth soils formed in glacial outwash. Mosher soils are drier and have layers in the C horizon that contain more fine sand. Wood River soils have a thicker A horizon and have a less clayey C horizon. Irwin, Labette, and Ladysmith soils lack a natric horizon. Mento soils have a less clayey B2t horizon and are in areas receiving less precipitation.

GEOGRAPHIC SETTING: Dwight soils typically are on upland divides, but a few are on foot slopes. The slope gradient ranges from 0 to 3 percent. The soils formed in clayey sediments derived largely from clay shales influenced with loess or old alluvium. The mean annual temperature varies from 53 to 57 degrees F, and the mean annual precipitation varies from 27 to 36 inches. Thornthwaites Annual P-E Index ranges from 48 to 64.

GEOGRAPHICALLY ASSOCIATED SOILS: These are Florence, Irwin, Labette, Ladysmith, and Sogn soils. Florence and Sogn soils are below Dwight soils. Florence soils are clayey-skeletal, and Sogn soils have limestone bedrock at depths less than 20 inches. Irwin and Ladysmith are above Dwight soils. Labette soils are on similar topographic positions as Dwight soils.

DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium. Permeability is very slow. Occasional small depressional areas pond water for several days.

USE AND VEGETATION: Used for native range. Native vegetation is mid and tall prairie grasses.

DISTRIBUTION AND EXTENT: Eastern Kansas and northeast Oklahoma. The soils of this series are of large extent, about 275,000 acres.


SERIES ESTABLISHED: Geary County, Kansas, 1957.

ADDITIONAL DATA: Two pedons are described in Soil Survey Investigation Report No. 4, pg. 14 to 17.

National Cooperative Soil Survey