LOCATION ARMSTER MO+IA KSEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Mollic Hapludalfs
TYPICAL PEDON: Armster loam - on a convex 7 percent slope in cultivated crops. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; very dark grayish brown (10YR 3/2) loam, grayish brown (10YR 5/2) dry; moderate very fine granular structure; very friable; many fine roots; moderately acid; abrupt smooth boundary. (6 to 10 inches thick)
BE--6 to 10 inches; brown (7.5YR 5/4) clay loam; common fine prominent red (2.5YR 4/8) mottles; moderate very fine subangular blocky structure; firm; many fine roots; common material from horizon above; weak stone line in lower part; strongly acid; clear smooth boundary. (0 to 7 inches thick)
2Bt1--10 to 16 inches; brown (7.5YR 5/4) clay; many fine prominent red (2.5YR 4/8) mottles; moderate very fine subangular blocky structure; firm; common fine roots; many faint clay films on faces of peds; common fine pebbles; very strongly acid; gradual smooth boundary.
2Bt2--16 to 28 inches; yellowish brown (10YR 5/4) clay; common fine prominent red (2.5YR 4/8) mottles; moderate very fine subangular blocky structure; firm; few fine roots; many faint clay films on faces of peds; common fine pebbles; strongly acid; gradual smooth boundary.
2Bt3--28 to 36 inches; yellowish brown (10YR 5/4) clay; common fine prominent red (2.5YR 4/8) mottles and few fine faint grayish brown (10YR 5/2) mottles; moderate very fine subangular blocky structure; firm; few fine roots; many faint clay films on faces of peds; common fine pebbles; strongly acid; clear smooth boundary. (Combined thickness of the 2Bt horizons is 20 to 48 inches.)
2BC--36 to 52 inches; yellowish brown (10YR 5/6) clay; common medium prominent gray (10YR 6/1) mottles; weak very fine subangular blocky structure; firm; common fine pebbles; moderately acid; clear smooth boundary. (0 to 18 inches thick)
2C--52 to 60 inches; yellowish brown (10YR 5/6) clay loam; few medium prominent gray (10YR 6/1) mottles; massive; firm; common black stains; common fine pebbles; slightly acid.
TYPE LOCATION: Montgomery County, Missouri; 4 miles north and 10 miles east of Montgomery City; 1620 feet north of the southwest corner; sec. 1, T. 49 N., R. 4 W.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to about 80 inches. There commonly is a weak pebble line at the top of the 2Bt horizon. Some pedons have a cobbly surface.
The Ap or A horizon has hue of 10YR or 7.5YR; value of 2 or 3, 4 or 5 dry and chroma of 1 to 3. It is silt loam, loam, or clay loam. Reaction is very strongly acid to neutral. Uneroded pedons have an E horizon up to 6 inches thick.
The BE horizon has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 3 to 5. It is silt loam, loam, or clay loam and very strongly acid to neutral.
The 2Bt horizon has hue of 5YR to 2.5Y, value of 4 to 6, and chroma of 4 to 8 in the upper part and value of 5 or 6 and chroma of 2 to 8 in the lower part and in the 2BC and 2C horizons. There are 5YR or redder hues within the upper part of the argillic horizon as either matrix color or mottles. Texture of the 2Bt and 2BC horizons is clay loam or clay. The upper 20 inches of the argillic horizon averages 36 to 48 percent clay and more than 20 percent sand. Reaction is very strongly acid to neutral. The 2C horizon is clay loam, loam or silty clay loam with more than 15 percent sand. Reaction is slightly acid to mildly alkaline.
COMPETING SERIES: These are the Kilkenny and Ladoga soils. Kilkenny soils do not have 5YR hue in the upper part of the argillic horizon. Ladoga soils have less than 5 percent sand throughout the solum and have less red colors in the upper part of the argillic horizon.
GEOGRAPHIC SETTING: Armster soils are on the upper valley convex side slope and low convex ridge positions where geologic erosion has exhumed the late Sangamon paleosol formed in glacial till. Slope gradients dominantly range from 5 to 12 percent but have an extreme range of 2 to 25 percent. Armster soils formed in reddish-colored late Sangamon paleosols, but the upper 7 to 20 inches above the pebble band on top of the paleosol is loess or loess and pedisediment. The mean annual temperature ranges from 47 to 57 degrees F, and mean annual precipitation ranges from 32 to 42 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Ladoga soils and the Kilwinning, Gara, Lagonda, and Mexico soils. Ladoga soils are upslope from the Armster soils. Kilwinning soils have less than 5 percent sand throughout and are on higher positions. Gara soils are fine-loamy and are on lower slopes. Lagonda soils have mollic epipedons and are on higher positions. Mexico soils have less than 5 percent sand in the upper 30 inches of the profile and are on higher positions.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium to rapid. Permeability is moderately slow. A perched water table has an upper limit of 3 to 5 feet during November to March.
USE AND VEGETATION: Corn, soybeans, grain sorghum, and wheat are the principal crops. Some areas are used for hay or pasture. A small area is forested. Native vegetation is deciduous trees and tall prairie grasses.
DISTRIBUTION AND EXTENT: Northern Missouri and northeastern Kansas. The series is of large extent.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Scotland County, Missouri, 1969.
REMARKS: Diagnostic horizons and features recognized in the series are: ochric epipedon - the zone from the surface of the soil to a depth of 10 inches (Ap and BE horizons); argillic horizon - the zone from approximately 10 to 36 inches (2Bt1, 2Bt2, and 2Bt3 horizons).