LOCATION VALPAC CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Fluvaquentic Haploxerolls
TYPICAL PEDON: Valpac loam - on a plane east facing slope of less than 1 percent in a cultivated vineyard at an elevation of 10 feet. When described October 20, 1978, the soil was dry to 9 inches and moist below. (Colors are for dry soil unless otherwise stated).
Ap1--0 to 10 inches; grayish brown (2.5Y 5/2) loam, very dark grayish brown (10YR 3/2) moist, very dark gray (10YR 3/1) moist, rubbed; weak medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; common very fine tubular pores; neutral (pH 7.0); clear wavy boundary. (5 to 16 inches thick)
Ap2--10 to 19 inches; mixed gray (10YR 5/1) and light yellowish brown (10YR 6/4) silt loam; very dark gray (10YR 3/1) and yellowish brown (10YR 5/4) moist; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; common very fine and fine interstitial and many very fine tubular pores; many worm casts, slightly alkaline (pH 7.6 CR); clear wavy boundary. (0 to 9 inches thick)
Ab--19 to 29 inches; light gray (10YR 6/1) loam, very dark grayish brown (10YR 3/2) moist; weak coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine and common fine tubular and common very fine interstitial pores; common worm casts, slightly alkaline (pH 7.4 CR); clear wavy boundary. (0 to 10 inches thick)
C--29 to 35 inches; light brownish gray (2.5Y 6/2) sandy loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine tubular and interstitial and common fine tubular pores; slightly alkaline (pH 7.4 CR); clear wavy boundary. (6 to 18 inches thick)
A'b--35 to 41 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (10YR 4/2) moist; few fine distinct reddish yellow (7.5YR 6/6) mottles, strong brown (7.5YR 5/6) mottles, moist; weak coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine tubular and common very fine interstitial pores; slightly alkaline (pH 7.4 CR); clear wavy boundary. (5 to 16 inches thick)
C'1--41 to 55 inches; light brownish gray (2.5Y 6/2) loam, dark grayish brown (2.5Y 4/2) moist; few medium distinct brownish yellow (10YR 6/6) mottles, yellowish brown (10YR 5/8) mottles, moist; weak coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine tubular and common very fine interstitial pores; slightly alkaline (pH 7.4 CR); clear wavy boundary. (10 to 14 inches thick)
C'2--55 to 61 inches; light brownish gray (2.5Y 6/2) silt loam, dark grayish brown (2.5Y 4/2) moist; few medium distinct reddish yellow (7.5YR 6/8) mottles, strong brown (7.5YR 5/8) mottles, moist; weak coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine interstitial and tubular pores; moderately alkaline (pH 7.9 CR).
TYPE LOCATION: Sacramento County, California; about 0.4 miles north of Hood, 3,450 feet north and 400 feet west of the southeast corner of section 15, T.6 N., R.4 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at a depth of 20 inches is 62 to 65 degrees F and the temperature remains above 47 degrees F throughout the year. The soil is dry between 6 and 19 inches in most years from June 15 to October 15, moist in all parts from December 1 to May 15 and moist in some part the rest of the year. The difference between mean summer and mean winter soil temperature ranges from 30 to 33 degrees F. If undrained, these soils are saturated at a depth of 36 to 40 inches for 90 consecutive days from about December through April in most years. Weighted average clay content for the 10 to 40 inch control section is 20 to 35 percent and fine sand and coarser material is greater than 15 percent. The mollic epipedon is 10 to 20 inches thick. Organic matter is 1 to 3 percent in the upper 10 inches and decreases irregularly with depth. One or more buried A horizons are at a depth of 20 to 40 inches. These soils are noncalcareous.
The Ap horizons are 10YR 5/2, 5/1, 4/2, 4/1; or 2.5Y 5/2. Moist color is 10YR 3/2, 3/1, or 2/2. Overwash material with dry color of 10YR 6/4 and moist color of 10YR 5/4 may be mixed in some pedons. Texture of lower subhorizons is loam, silt loam or clay loam with 18 to 35 percent clay. Reaction is neutral to slightly alkaline.
The C horizon is 10YR 7/2, 7/1, 6/3, 6/2; or 2.5Y 6/2. Moist color is 10YR 5/2, 4/3, 4/2, 4/1, 3/2 or 2.5Y 4/2. It is stratified fine sandy loam, sandy loam, loam, silt loam or clay loam with 15 to 30 percent clay. Reaction is slightly to moderately alkaline.
The Ab and A'b horizons are 10YR 6/1, 5/2, 5/1, 4/1; or 2.5Y 6/2. Moist color is 10YR 4/2, 3/2, 3/1, 2/2, or 2/1. Texture is loam, clay loam or silty clay loam with 20 to 35 percent clay. Reaction is slightly to moderately alkaline.
The C' horizon is similar in texture, color and reaction to the 2C horizon.
COMPETING SERIES: These are Blucher, Pacheco and Lakeside soils in the same family and Mocho and Nueva soils. Blucher and Pacheco soils have a difference of 15 to 18 degrees F, respectively, between the mean summer and mean winter soil temperature. Lakeside soils are calcareous and saline-alkali and are moist for 120 consecutive days. Mocho soils are calcareous and lack buried A horizons. Nueva soils lack clay loam layers above 40 inches have moderate permeability above 40 inches and if undrained, have a water table below 40 inches.
GEOGRAPHIC SETTING: Valpac soils are on natural levees of high floodplains. Elevation is 5 to 25 feet. Slopes are 0 to 2 percent. These soils formed in alluvium from mixed rock sources. The climate is dry subhumid with hot dry summers and cool moist winters. Mean annual precipitation is 15 to 18 inches. The average January temperature is 46 degrees F, the average July temperature is 76 degrees F and the mean annual temperature is 60 to 63 degrees F. The frost-free season is about 275 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Egbert, Sailboat and Scribner soils. Egbert soils have a fine particle-size control section and are lower on the flood plain. Sailboat soils have an ochric epipedon and are on natural levees of the low flood plain. Scribner soils have a mollic epipedon greater than 24 inches thick and are on edges of backswamps.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; moderately slow permeability. These soils are artificially drained. A seasonal water table occurs from December through April at a depth of 36 to 60 inches. These soils are protected by levees and the hazard of flooding is rare.
USE AND VEGETATION: Used for growing irrigated crops such as pears, grapes, wheat, corn, tomatoes and irrigated pasture.
DISTRIBUTION AND EXTENT: The lower Sacramento Valley. Soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Sacramento County, California, 1986.
REMARKS: The activity class was added to the classification in March of 2003. Competing series were not checked at that time. - ET
Diagnostic horizon and features recognized in this pedon are:
Mollic epipedon - 0 to 19 inches (Ap horizons)
Fluvaquentic - organic matter content decreases irregularly with depth. If undrained, these soils are saturated at a depth of 36 to 40 inches for 90 consecutive days.