LOCATION MALVERN IA+MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquic Argiudolls
TYPICAL PEDON: Malvern silty clay loam with a convex, northeast-facing slope of about 11 percent - pasture. (Colors are for moist soil unless otherwise stated.)
A1--0 to 10 inches; very dark brown (10YR 2/2) silty clay loam, very dark grayish brown (10YR 3/2) dry; weak fine and very fine granular structure; friable; many roots and fine pores; medium acid; clear smooth boundary.
A2--10 to 16 inches; very dark grayish brown (10YR 3/2) silty clay loam, grayish brown (10YR 5/2) dry; moderate fine and very fine subangular blocky structure; friable; very dark brown (10YR 2/2) coatings on peds and in root channels; many roots and fine pores; slightly acid; clear smooth boundary. (Combined thickness of the A horizons is 10 to 20 inches.)
2Bt1--16 to 26 inches; brown (7.5YR 4/4) silty clay; few fine distinct strong brown (7.5YR 5/6) and grayish brown (2.5Y 5/2) mottles; strong fine subangular blocky structure; very firm; some mixing or worm casts of very dark gray (10YR 3/1); thin discontinuous dark brown (7.5YR 3/2) clay films; many roots and fine pores; slightly acid; clear smooth boundary.
2Bt2--26 to 40 inches; reddish brown (5YR 4/4) and brown (7.5YR 4/4) silty clay; common medium distinct reddish gray (5YR 5/2) and few fine prominent light gray (10YR 7/1) mottles; moderate medium prismatic structure parting to strong medium and fine subangular blocky; very firm; very dark gray (10YR 3/1) fillings in some pores; thick nearly continuous dark brown (7.5YR 3/2) clay films; few roots and fine pores; slightly acid; clear smooth boundary.
2Bt3--40 to 54 inches; strong brown (7.5YR 5/8) and reddish brown (5YR 5/4) silty clay; common fine distinct dark reddish gray (5YR 4/2), common medium distinct reddish gray (5YR 5/2), and many large prominent light gray (10YR 7/1) mottles; weak coarse prismatic structure parting to moderate medium subangular blocky; firm; some dark stains and fine concretions (Fe-Mn); few pores; neutral. (Combined thickness of the 2Bt horizons is 26 to 46 inches.)
2C--54 to 60 inches; brown (7.5YR 4/4) and reddish brown (5YR 5/4) silty clay loam; mottles same as above; massive; firm; stains and concretions same as above; neutral.
TYPE LOCATION: Fremont County, Iowa; about 6 miles south of Shenandoah; 1,840 feet west and 75 feet south of the NE corner of sec. 26, T. 68 N., R. 40 W.
RANGE IN CHARACTERISTICS: Solum thickness commonly ranges between 36 and 66 inches. Typically, carbonates are absent to a depth of many feet below the solum; however, some pedons have carbonates oriented along cleavage faces in the lower part of the 2Bt horizon. The solum typically averages between 5 and 15 percent sand.
The A horizon has hue of 10YR or 7.5YR, value of 2 or 3, and chroma of 2 or 3. It is silty clay loam with a clay content ranging from 28 to 34 percent. The A horizon typically is medium or slightly acid but ranges to neutral in some pedons.
The 2Bt horizon typically has hue of 7.5YR, 5YR, or 10YR, value of 4 or 5, and chroma of 3 through 8. If the matrix has 10YR hue, reddish mottles are in the 2Bt horizon and range in abundance from common to many. Few to many mottles with value of 4 through 7 and chroma of 1 or 2 are in the 2Bt horizon. Mottles increase in size and abundance with depth. The 2Bt horizon is silty clay with a clay content ranging from 40 to 50 percent. Clay films are distinctly evident, but many of these are probably related to the paleosol rather than the present modern soil. Many of the properties of the B horizons are believed to be inherited from the exhumed paleosol. B/A clay ratios are greater than 1.2. The 2Bt horizon typically is slightly acid or neutral. A 2BC horizon is in some pedons.
The 2C horizon has hue of 10YR, 7.5YR, or 5YR, value of 4 to 6, and chroma of 4 through 8. The average clay content typically is 28 to 35 percent but the range is to 38 percent. It is slightly acid or neutral.
COMPETING SERIES: These are the Adair, Arispe, Chase, Flanagan, Greenton, Grundy, Herrick, Ipava, Keller, Lagonda, Lamoni, Macksburg, Mahaska, Martin, Mayberry, Pawnee, Rutland, Seymour, Shorewood, Tina, and Wymore soils in the same family. All of these soils except the Adair and Mayberry soils are less red in hue. Adair soils contain more that 15 percent sand in the solum and, in addition, have a stone line in the upper part of the B horizon. Mayberry soils typically have thicker sola and, in addition, contain more sand throughout the solum and more clay in the lower part of the solum.
GEOGRAPHIC SETTING: Malvern soils are on low convex summits of narrow interfluves and convex sideslopes on uplands. They most commonly occur as a narrow band on sideslopes where geologic erosion has exhumed the Sangamon paleosols. Slope gradients range from 5 to 14 percent. These soils formed in Sangamon paleosols formed in Loveland loess, except the upper 10 to 20 inches formed from Wisconsin loess. Mean annual temperature ranges from about 49 to 54 degrees F, and mean annual precipitation ranges from about 28 to 34 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Adair soils and the Ida, Marshall, Monona, and Shelby soils. Ida, Marshall, and Monona soils lack the reddish hues and silty clay textures and are on slopes above the Malvern soils. Adair and Shelby soils are downslope and contain more sand and gravel-size material.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. Permeability is slow. Surface runoff is medium to rapid.
USE AND VEGETATION: Commonly cropped to corn, soybeans, small grains, and legume hays. Some areas are in pasture. Native vegetation was tall prairie grasses.
DISTRIBUTION AND EXTENT: Malvern soils are limited to the extreme southwestern part of Iowa and possibly in southeastern Nebraska and northeastern Kansas. They are inextensive; about 4,000 to 8,000 acres occur in Iowa.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Fremont County, Iowa, 1978.
REMARKS: Colors are assumed to be derived mainly from the paleosol rather than from present drainage conditions. The best placement is thought to be Aquic Argiudolls.