LOCATION HESSON WAEstablished Series
TAXONOMIC CLASS: Fine, kaolinitic, mesic Xeric Palehumults
TYPICAL PEDON: Hesson clay loam - pasture. (Colors are for moist soil unless otherwise noted.)
A1--0 to 8 inches; dark reddish brown (5YR 2/2) clay loam, dark brown (7.5YR 4/2) dry; strong very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; many fine and medium irregular pores; very strongly acid (pH 5.0); clear smooth boundary. (5 to 9 inches thick)
A2--8 to 12 inches; dark reddish brown (5YR 3/2) clay loam, brown (7.5YR 5/4) dry; strong fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; few medium and common very fine and fine irregular pores; moderately acid (pH 5.8); clear smooth boundary. (4 to 9 inches thick)
BAt--12 to 22 inches; dark reddish brown (5YR 3/3) clay loam, dark brown (7.5YR 4/4) dry; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; common fine roots; common fine and medium irregular pores; continuous distinct clay films on faces of peds and in pores; strongly acid (pH 5.4); clear wavy boundary. (8 to 12 inches thick)
Bt1--22 to 30 inches; reddish brown (5YR 4/4) clay, dark brown (7.5YR 4/4) dry; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; common fine roots; common fine and medium irregular pores; continuous distinct clay films on faces of peds and in pores; few, medium, prominent, black (5YR 2/1) mineral stains; strongly acid (pH 5.4); gradual wavy boundary. (8 to 10 inches thick)
Bt2--30 to 40 inches; reddish brown (5YR 4/3) clay, brown (7.5YR 5/4) dry; moderate medium prismatic structure; slightly hard, friable, sticky and plastic; few fine roots on ped surfaces; common medium tubular pores; continuous distinct clay films on faces of peds and in pores; few, medium, prominent, black (5YR 2/1) mineral stains; strongly acid (pH 5.4); gradual wavy boundary. (10 to 15 inches thick)
Bt3--40 to 60 inches; reddish brown (5YR 4/3) clay, dark brown (.5YR 4/4) dry; moderate medium prismatic structure; hard, firm, sticky and plastic; few fine roots on surface of peds; common medium and fine tubular pores; continuous distinct clay films on faces of peds and in pores; few, medium prominent black (5YR 2/1) mineral stains; very strongly acid (pH 4.9); gradual wavy boundary. (17 to 22 inches thick)
Bt4--60 to 80 inches; reddish brown (5YR 4/3) dark brown (7.5YR 4/4) dry; moderate medium and coarse prismatic structure; very hard, firm, sticky and plastic; common fine and medium tubular pores; continuous distinct clay films on faces of peds and in pores; very strongly acid (pH 5.0); clear smooth boundary. (20 to 25 inches thick)
Bt5--80 to 91 inches; reddish brown (5YR 4/3) clay, dark brown (7.5YR 4/4) dry; common medium distinct brown (10YR 5/3) mottles; moderate coarse prismatic structure; very hard, very firm, sticky, plastic; common coarse tubular pores; common distinct clay films on faces of peds and continuous distinct clay films in pores; few, medium, prominent, black (5YR 2/1) mineral stains; strongly acid (pH 5.5).
TYPE LOCATION: Clark County, Washington; 1,050 feet south and 200 feet west of the northeast corner of sec. 32, T. 3 N., R. 3 E.
RANGE IN CHARACTERISTICS: The umbric epipedon is 10 to 18 inches thick. The solum depth is more than 70 inches. Mean annual soil temperature ranges from 50 to 52 degrees F. The soils are usually moist but are dry in the moisture control section for 45 to 60 consecutive days following the summer solstice. The particle-size control section has 35 to 50 percent clay and 0 to 5 percent rounded quartzite pebbles.
The A horizon has hue of 5YR to 10YR, value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist. It is very strongly acid to moderately acid. It is gravelly in some pedons.
The Bt horizon has hue of 5YR or 7.5YR, value of 3 or 4 moist, 4 or 5 dry, and chroma of 3 through 6 moist and dry. It is silty clay loam, clay loam, or clay. Clay films range from few faint in the upper part continuous distinct in the part. Reaction is very strongly acid or strongly acid. Redox features occur below a depth of 60 inches in some pedons.
COMPETING SERIES: This is the Salkum series. Salkum soils have an ochric epipedon and have shot-like concretions in the A and AB horizons.
GEOGRAPHIC SETTING: The Hesson soils are on high terraces and terrace escarpments at elevations of 300 to 1,000 feet. Slopes are 0 to 55 percent. Hesson soils formed in old alluvium of quartzitic and basic igneous rock origin. The climate is mild; with warm, dry summers and cool, wet winters. The average annual precipitation is about 50 to 75 inches. The average January temperature is about 36 degrees F, the average July temperature is about 64 degrees F, and the mean annual temperature is 48 to 52 degrees F. The frost-free season is 160 to 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bear Prairie, Hillsboro, Minniece, Olequa, Olyic, Skoly, and Washougal soils. Bear Prairie soils are medial. Hillsboro and Olequa are fine-silty. Minniece soils have an aquic moisture regime and are poorly drained. Olyic soils are fine- loamy. Skoly soils are loamy-skeletal. Washougal soils are medial- skeletal.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used mainly for homesites, wildlife habitat and cropland. Hay, pasture, small grains and row crops are principal crops. Native vegetation is Douglas-fir, red alder, and western hemlock with an understory of vine maple, Oregon-grape, western brackenfern and grasses.
DISTRIBUTION AND EXTENT: Southwestern Washington; MLRA 2. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clark County, Washington; southwest Washington Reconnaissance Soil Survey, 1911.
REMARKS: Diagnostic horizons and features recognized in this pedon are an umbric epipedon from the surface to 12 inches and an argillic horizon from 12 to 80 inches. This draft reflects a change in classification by adding CEC activity class.