LOCATION LAMONI IA+MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Argiudolls
TYPICAL PEDON: Lamoni silty clay loam with a west-facing convex slope of 9 percent - pasture. (Colors are for moist soil unless otherwise stated.)
A1--0 to 6 inches; black (10YR 2/1) silty clay loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky structure; friable; strongly acid; clear smooth boundary.
A2--6 to 11 inches; very dark grayish brown (10YR 3/2) clay loam, grayish brown (10YR 5/2) dry; faces of some peds very dark gray (10YR 3/1); moderate very fine subangular blocky and granular structure; friable; few black (10YR 2/1) worm casts; strongly acid; clear smooth boundary. (Combined thickness of the A horizons is 10 to 17 inches.)
2Bt1--11 to 14 inches; brown (10YR 4/3) clay; faces of peds dark grayish brown (10YR 4/2); few fine faint dark yellowish brown (10YR 4/4) mottles; moderate fine subangular blocky structure; firm; few very dark gray (10YR 3/1) worm casts; strongly acid; gradual smooth boundary.
2Bt2--14 to 19 inches; dark grayish brown (10YR 4/2) clay; many fine distinct yellowish brown (10YR 5/6) and few fine distinct strong brown (7.5YR 5/6) mottles; moderate fine subangular blocky structure; very firm; thin continuous clay films; some weatherable minerals; medium acid; gradual smooth boundary.
2Bt3--19 to 25 inches; grayish brown (2.5Y 5/2) clay; common fine distinct yellowish brown (10YR 5/6) and few fine prominent strong brown (7.5YR 5/6) mottles; moderate fine subangular blocky structure; very firm; thick continuous clay films; dark brown (7.5YR 3/2) concretions (oxides); few small pebbles; some weatherable minerals; medium acid; gradual smooth boundary.
2Bt4--25 to 33 inches; mottled light brownish gray (2.5Y 6/2), light gray (5Y 6/1), and yellowish brown (10YR 5/6) clay; moderate medium prismatic structure parting to weak medium subangular blocky; firm; thin discontinuous clay films on faces of prisms; common black (10YR 2/1) and dark brown (7.5YR 3/2) concretions (oxides); few small pebbles; medium acid; gradual smooth boundary. (Combined thickness of the 2Bt horizons is 16 to 30 inches.)
2BC--33 to 55 inches; yellowish brown (10YR 5/6) clay loam; common medium distinct light gray (5Y 6/1) and few medium faint strong brown (7.5YR 5/8) mottles; moderate medium prismatic structure parting to weak medium subangular blocky; firm; thin discontinuous clay films; some very dark gray (10YR 3/1) around root channels; many black (10YR 2/1) and dark brown (7.5YR 3/2) concretions (oxides); few small pebbles; slightly acid; gradual smooth boundary. (19 to 25 inches thick)
2C--55 to 80 inches; yellowish brown (10YR 5/6) clay loam; common medium distinct light gray (5Y 6/1) and a few medium faint strong brown (7.5YR 5/8) mottles; massive; firm; many black (10YR 2/1) and dark brown (7.5YR 3/2) concretions (oxides); few small pebbles; neutral.
TYPE LOCATION: Wayne County, Iowa; about 7 miles east of Humeston; 2,440 feet west and 30 feet south of the northeast corner of sec. 22, T. 70 N., R. 22 W.
RANGE IN CHARACTERISTICS: Solum thickness typically is 4 to 6 feet. The soil typically is medium acid to strongly acid in the most acid part, but the range includes slightly acid. Some pedons contain carbonates below a depth of 48 inches.
The A horizon has hue of 10YR, value of 2 or 3, and chroma of 1 or 2. It typically is silty clay loam, but the range includes loam, silt loam, clay loam, and clay.
The upper part of the 2Bt horizon typically has hue of 10YR or 2.5Y, value of 4, dominant chroma of 2, and mottles of higher chroma. The lower part has hue of 10YR through 5Y, value of 5 or 6, and chroma of 1 through 6. The amount of high chroma increases with depth. The color and texture of the 2Bt horizon are variable and related principally to the amount of truncated paleosol remaining. Hues redder than 10YR are restricted to mottles or oxides.
The part of the B horizons of clay texture typically is 12 to 24 inches thick, and the finest part contains between 40 and 50 percent clay. Depth to the finest part usually ranges from 10 to 18 inches but decreases as gradient increases on convex slopes. The amount of sand and small pebbles increase as depth increases. The upper part of the solum contains between 15 and 30 percent sand and the lower part and the C horizon between 30 and 45 percent.
COMPETING SERIES: These are the Adair, Arispe, Chase, Flanagan, Greenton, Grundy, Herrick, Ipava, Lagonda, Macksburg, Mahaska, Malvern, Martin, Mayberry, Pawnee, Rutland, Seymour, Shorewood, and Wymore series in the same family and the Clarinda, Clearfield, Coatsburg, Lineville, Sampsel, and Shelby soils. Adair soils lack mottles with chroma of 1 in the lower part of the B horizon and in the C horizon, have 7.5YR or redder hue in the matrix of the upper part of the Bt horizon, and typically have a pebble band in the upper part of the B horizon. Arispe, Flanagan, Greenton, Grundy, Herrick, Ipava, Macksburg, Mahaska, Rutland, Seymour, Wymore, and Clearfield soils have less sand and lack any pebbles in the upper 3 feet of the sola. Chase soils have a mollic epipedon more than 24 inches thick. Lagonda soils typically have less sand and lack pebbles in the upper part of the B horizon. Malvern and Mayberry soils have 7.5YR or redder hue in much of the B horizon. Martin soils formed in weathered shale. Pawnee soils typically have a thicker B horizon and a less acid solum. Shorewood soils have a thinner, less acid solum and contain free carbonates within a depth of 40 inches. Clarinda soils have clay or silty clay textures 3 feet or more thick. Coatsburg soils have grayer colors directly below the mollic epipedon and contain more illite in the lower part of the solum and C horizon. Lineville soils lack a mollic epipedon and are deeper to the horizon highest in clay. Sampsel soils have grayer colors directly below the mollic epipedon. Shelby soils have higher chroma in the upper part of the B horizon and are fine-loamy.
GEOGRAPHIC SETTING: The Lamoni soils typically are on moderately sloping convex side-valley slopes surrounding the nearly level, stable, upland divides. Slope gradients range from about 5 to 18 percent. Lamoni soils formed in partially truncated, exhumed, grayish brown, clayey paleosols which were formed in Yarmouth-Sangamon time in glacial till of Kansan age and were partially truncated prior to the recent cycle of soil development. The A horizon formed in loess or a mixture of loess and pedisediment. Mean annual temperature is about 49 to 53 degrees F, and mean annual precipitation is about 30 to 35 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Clarinda and Shelby soils. Clarinda soils commonly are upslope and the Shelby soils downslope. Generally the three soils cannot be mapped on the same slope; however, where the loess is thin, the Clarinda soils are on secondary interfluves or at the shoulder of side slopes in many places and the Lamoni soils are on side slopes. Where slopes are long, both Lamoni and Shelby soils are commonly on the same side slope. On steep slopes, Lamoni soils are usually on the interfluves or shoulders of slopes and the Shelby soils are on the entire side slope.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. Lamoni soils are seasonally wet and seepy. Runoff is medium or rapid. Permeability is slow or very slow. Depth to an intermittent perched water table is 1 to 3 feet at some time from November through July in most years.
USE AND VEGETATION: Generally cultivated; main crops are corn, oats, hay, or pasture. Native vegetation was tall prairie grasses.
DISTRIBUTION AND EXTENT: Southern Iowa and northern Missouri. They are extensive.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Scotland County, Missouri, 1969.
REMARKS: Classification only was updated 3/94 for final correlations in Iowa. Changes include proposals made in Amendment 17 of Soil Taxonomy. Competing series and other updates will be made later. Diagnotic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface to a depth of 11 inches (A1 and A2 horizons); argillic horizon - the zone from 11 to 33 inches (2Bt1, 2Bt2, 2Bt3, and 2Bt4 horizons); aquic moisture regime.