LOCATION PECKHAM CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, active, thermic Typic Haploxeralfs
TYPICAL PEDON: Peckham cobbly loam - on a slope of 3 percent, under tarweed, soft chess and medusahead at an elevation of 1,560 feet. (Colors are for dry soil unless otherwise stated. When described on September 22, 1981, the soil was slightly moist below 20 inches.)
A1--0 to 2 inches; brown (7.5YR 5/4) cobbly loam, dark reddish brown (5YR 3/4) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and plastic; common very fine roots; common very fine tubular pores; 10 percent cobbles and 5 percent stones; 1.4 percent organic matter; 12 percent clay content; moderately acid (pH 6.0); clear smooth boundary. (1 to 5 inches thick)
A2--2 to 13 inches; brown (7.5YR 5/4) cobbly loam; dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; common very fine roots; common very fine and fine tubular pores; 10 percent cobbles and 5 percent stones; 0.9 percent organic matter; 16 percent clay content; slightly acid (pH 6.5); clear smooth boundary. (8 to 14 inches thick)
Bt1--13 to 20 inches; strong brown (7.5YR 4/6) very cobbly heavy loam, dark reddish brown (5YR 3/3) moist; common fine and medium subangular blocky structure; slightly hard, friable, very sticky and plastic; few very fine roots; few fine, common medium, and few coarse tubular pores; common moderately thick clay films line pores, common thin clay films bridging sand grains, and few thin clay films on peds; 35 percent cobbles and 15 percent stones; 0.5 percent organic matter; 24 percent clay content; slightly acid (pH 6.5); abrupt smooth boundary. (6 to 11 inches thick)
2Bt2--20 to 24 inches; strong brown (7.5YR 4/6) extremely cobbly clay, dark brown (7.5YR 3/4) moist; massive; hard, firm, sticky and very plastic; few medium and coarse roots; few very fine and fine tubular pores; many thick clay films line pores and bridge sand grains; 30 percent gravel, 25 percent cobbles, and 15 percent stones; 51 percent clay content; slightly acid (pH 6.5); abrupt smooth boundary. (1 to 4 inches thick)
3R--24 to 28 inches; hard fractured volcanic tuff conglomerate.
TYPE LOCATION: Merced County, California; about 20 miles SW of the city of Los Banos, 2,600 feet north of Pfieffer ranch house, 120 feet east of fence on north side of dirt road, 3,000 feet east and 2,600 feet north of the SE corner of section 13, T. 12 S., R. 7 E. UTM 10 666083e and 4084197n NAD83.
RANGE IN CHARACTERISTICS: Depth to hard fractured volcanic tuff conglomerate is 20 to 30 inches. The moisture control section of 7 to 20 inches is moist throughout from about November 15 to May 15 and dry throughout from about June 15 to October 15 in most years. The soil temperature is below 47 degrees F. from January 1 to March 1. The mean annual soil temperature is 59 to 62 degrees F. Organic matter content ranges up to 2 percent in the A horizon but is below 1 percent within 4 inches of the surface. The average clay content of the argillic horizon is 20 to 35 percent. There is an abrupt boundary between the upper Bt1 horizon and the lower 2Bt2 horizon. Reaction remains the same or increases slightly with depth.
The A horizon dry color is 5YR 5/3, 5/4; 7.5YR 5/4, or 5/6. Moist colors are 5YR 3/3, 3/4, 4/4; 7.5YR 3/4, 3/6, 4/4, or 4/6. It has 10 to 20 percent clay content and 15 to 35 percent cobbles and stones and 0 to 5 percent gravel. Reaction is moderately acid to neutral.
The Bt1 horizon dry color is 5YR 4/4, 4/6; 7.5YR 4/4, 4/6, or 5/6. Moist colors are 5YR 3/3, 3/4; 7.5YR 3/4, 3/6, 4/4, or 4/6. It is very cobbly loam or very cobbly sandy clay loam and has 18 to 28 percent clay content. It has 40 to 60 percent cobbles and stones and 0 to 5 percent gravel. Reaction is moderately acid to neutral.
The 2Bt2 horizon is 7.5YR 4/4, 4/6, 5/4, 5/6; 10YR 4/6, 5/4, or 5/6. Moist colors are 7.5YR 3/4, 3/6, 4/4, 4/6; 10YR 4/3, 4/4, or 4/6. It has 40 to 60 percent clay content and 70 to 80 percent cobbles, stones, and gravel. Reaction is slightly acid or neutral.
COMPETING SERIES: This is the Yorba series in the same family and the Agua Dulce and Bally series in other families. Agua Dulce soils have over 1 percent organic matter at a depth of 4 inches and lack a paralithic contact within a depth of 60 inches. Bally soils are clayey-skeletal. Yorba soils are greater than 60 inches deep.
GEOGRAPHIC SETTING: Peckham soils are on hillslopes in mountains and have slopes of 2 to 50 percent. Elevations range from 700 to 3,400 feet. The soils formed in material weathered from volcanic tuff conglomerate of the Quien Sabe Formation. Cobbles and stones typically cover 5 to 20 percent of the soil surface but some areas have had surface cobbles and stones removed. 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 Ararat, Franciscan, Laveaga, and Quinto soils. Ararat soils are 40 to 50 inches deep and have a mollic epipedon. Franciscan soils are fine-loamy, 20 to 40 inches deep, and have a mollic epipedon. Laveaga soils have a mollic epipedon and a mesic temperature regime. Quinto soils are loamy and less than 20 inches deep.
DRAINAGE AND PERMEABILITY: Well drained, slow to rapid runoff, slow permeability.
USE AND VEGETATION: These soils are used for annual rangeland and as upland wildlife habitat. The vegetation is tarweed, soft chess, medusahead, and other annual 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.
REMARKS: These soils were formerly mapped as Rough stony land and Surprise stony sandy loam in the Los Banos Area, series 1939 report. They are being differentiated from the Surprise series by having an argillic horizon and not having a mollic epipedon. pH determined by colorimetric method using Thymol Blue and Hellige-Truog triplex indicators. Texture determined by hydrometer method. Organic carbon determined by Walkley-Black digestion method. The 2Bt2 horizon is too thin for this soil to classify in the clayey-skeletal family. Base saturation determined by KLC-triethanolamine extract (sum of cations).
The activity class was added to the classification in January of 2003. Competing series were not checked at that time. Lab data should be obtained to properly identify the mineralogy of this soil, possible isotic - ET
OSED scanned by SSQA. Last revised by state on 8/84.