LOCATION ILLITO CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Lithic Argixerolls
TYPICAL PEDON: Illito extremely stony loam - on a southeast facing slope of 41 percent under filaree, burclover, softchess, tarweed and other grasses and forbs at an elevation of 1,680 feet. (Colors are for dry soil unless othersie stated. When described on September 23, 1981, the soil was dry throughout.)
A--0 to 5 inches; dark brown (10YR 4/3) extremely stony loam, very dark grayish brown (10YR 3/2) moist; strong medium and coarse angular blocky structure; hard, friable, sticky and plastic; common very fine roots concentrated along vertical faces of peds; common very fine tubular pores; 10 percent angular gravel 2 to 5 mm in size and 35 percent stones and cobbles; 79 percent base saturation (sum of cations); slightly acid (pH 6.5); abrupt smooth boundary. (2 to 6 inches thick)
Bt--5 to 8 inches; dark brown (7.5YR 4/2) very stony clay, dark brown (7.5YR 3/2) moist; strong medium and coarse prismatic structure; very hard, firm, sticky and very plastic; few very fine roots concentrated along vertical faces of peds; common very fine tubular pores; many thick clay films on peds; few thin clay films bridge sand grains and in pores; 10 percent angular gravel 2 to 5 mm in size and 40 percent stones and cobbles; organic matter is 1.1 percent; neutral (pH 7.0); abrupt wavy boundary. (3 to 5 inches thick)
R--8 inches; hard, unweathered basic volcanic rock.
TYPE LOCATION: Merced County, California; about 20 miles southwest of the city of Los Banos, 1,400 feet south and 600 feet west of the NE corner of Section 29, T. 12 S., R. 8 E., projected section lines from Section 5, T. 13 S., R. 8 E.
RANGE IN CHARACTERISTICS: Stones cover 15 to 50 percent of the surface. Depth to a lithic contact ranges from 5 to 10 inches. The mean annual soil temperature is 60 degrees F to 66 degrees F. The soil temperature is below 47 degrees F from January 1 to March 1. The soil at the lithic contact is moist from November 1 to May 1 and is dry the rest of the year. The mollic epipedon extends into the Bt horizon and is the same thickness as the solum. Organic matter is 1 to 2 percent. Reaction is slightly acid or neutral throughout. Rock fragments (gravel, cobbles, and stones) range from 35 to 60 percent throughout.
The A horizon is 7.5YR 5/4; 10YR 4/3 or 5/3. Moist colors are 7.5YR 3/2; 10YR 2/2 or 3/2. Clay content ranges from 20 to 27 percent.
The Bt horizon is 7.5YR 4/2, 4/4 or 5/4 dry and 7.5YR 3/2 moist. It is very stony clay loam, very stony clay or very cobbly clay with 35 to 45 percent clay content. This horizon rests abruptly on hard, unweathered basic volcanic rock.
COMPETING SERIES: This is the Inks series in the same family and the , Hambright, Millerton, Pardee, Peckham, Quinto, Shorthorn, Temblor, Tunis and Tunehill series in other families. Inks soils have a lithic contact at a depth of 10 to 20 inches. Hambright and Temblor soils do not have an argillic horizon and have a lithic contact at a depth of 10 to 20 inches. Millerton and Pardee soils have an ochric epipedon and a lithic contact at a depth of 10 to 20 inches. Peckham soils have an ochric epipedon and a lithic contact at a depth of 20 to 30 inches. Quinto soils have a lithic contact at a depth of 10 to 20 inches and have have less than 35 percent coarse fragments in the texture control section. Shorthorn, Tunis and Tunehill soils have a paralithic contact at a depth of 10 to 20 inches and have less than 35 percent coarse fragments in the texture control section. Temblor soils do not have an argillic horizon.
GEOGRAPHIC SETTING: Illito soils are on hillslopes in mountains and have slopes of 30 to 75 percent. Elevations range from 1,000 to 3,800 feet. The soils formed in material weathered from basic volcanic rock of the Quien Sabe Formation. The climate is subhumid with hot dry summers and cool moist winters. The mean annual precipitation is about 13 to 24 inches. Mean January temperature is 45 degrees F; mean July temperature is 75 degrees F; mean annual temperature is about 61 degrees F. Frost-free season is 190 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Peckham and Quinto soils and Ararat, Asolt, Hytop, Laveaga and Lecrag soils. Ararat soils have a lithic contact at a depth of 40 to 50 inches. Asolt and Lecrag soils develop wide cracks when dry and are 40 to 60 inches deep. Hytop and Laveaga soils have a fine texture control section and a paralithic contact below 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; very slow permeability.
USE AND VEGETATION: These soils are used as rangeland and upland wildlife habitat. The vegetation is filaree, soft chess, foxtail fescue, tarweed, burclover, red brome, wild oats, and other grasses and forbs.
DISTRIBUTION AND EXTENT: These soils are in the Coast Range of California. They are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Merced County, California 1984. Name is coined.
REMARKS: These soils were formerly mapped as Rough stony land in the Los Banos Area, series 1939 report. pH determined by colorimetric method using Hellige Troug triplex indicators. Texture determined by hydrometer method. Organic carbon determined by Walkley-Black digestion method. Base saturation determined by KC1-triethanolamine extract (sum of cations). These soils are classified in the loamy-skeletal family because the texture control section averages less than 35 percent clay content.
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET