LOCATION POWVAL             OR
Established Series
Rev. MGL/AON/TDT
10/2002

POWVAL SERIES


The Powval series consists of deep, well drained soils on
stream terraces. They formed in mixed alluvium with an
influence of volcanic ash. Slope ranges from 0 to 3
percent. The mean annual temperature is about 48 degrees F,
and the mean annual precipitation is about 10 inches.

TAXONOMIC CLASS: Coarse-silty, mixed, superactive, mesic Pachic Haploxerolls

TYPICAL PEDON: Powval silt loam, on a 2 percent slope in a cultivated field. (Colors are for moist soil unless
otherwise noted.)

Apk--0 to 9 inches; very dark grayish brown (10YR 3/2)
silt loam, grayish brown (10YR 5/2) dry; weak fine granular structure; slightly hard, friable, slightly sticky and
slightly plastic; many very fine roots; common very fine
irregular pores; strongly effervescent; moderately alkaline
(pH 8.2); abrupt smooth boundary. (4 to 10 inches thick)

Ak--9 to 13 inches; very dark grayish brown (10YR 3/2)
silt loam, grayish brown (10YR 5/2) dry; weak coarse
subangular blocky structure; slightly hard, friable,
slightly sticky and slightly plastic; many very fine roots;
common very fine tubular pores; strongly effervescent;
moderately alkaline (pH 8.2); clear smooth boundary. (4 to
9 inches thick)

Bk1--13 to 32 inches; dark brown (10YR 3/3) silt loam,
grayish brown (10YR 5/2) dry; weak coarse prismatic and weak
coarse subangular blocky structure; slightly hard, friable,
slightly sticky and slightly plastic; common very fine
roots; common very fine tubular pores; strongly
effervescent; moderately alkaline (pH 8.4); abrupt smooth
boundary. (10 to 25 inches thick)

Bk2--32 to 41 inches; very dark grayish brown (10YR 3/2)
silt loam, grayish brown (10YR 5/2) dry; massive; hard,
firm, nonsticky and nonplastic; common very fine roots;
common very fine tubular pores; slightly effervescent;
moderately alkaline (pH 8.2); clear smooth boundary. (8 to
15 inches thick)

Bk3--41 to 56 inches; dark grayish brown (10YR 4/2) silt
loam, grayish brown (10YR 5/2) dry; many fine distinct dark
reddish brown (5YR 3/4) mottles; massive; hard, firm,
nonsticky and nonplastic; common very fine roots; common
very fine tubular pores; very slightly effervescent;
moderately alkaline (pH 8.2); clear smooth boundary. (15 to
20 inches thick)

C--56 to 60 inches; dark gray (10YR 4/1) silt loam,
grayish brown (10YR 5/2) dry; many fine distinct dark
reddish brown (5YR 3/4) mottles; massive; slightly hard,
friable, nonsticky and nonplastic; few very fine roots in
the upper part; many very fine and fine tubular pores;
mildly alkaline (pH 7.8).

TYPE LOCATION: Baker County, Oregon; 350 feet north and 40
feet east of Pocahontas Road and 17th Street intersection in
the SW1/4NW1/4 of sec. 8, T. 9 S., R. 40 E.

RANGE IN CHARACTERISTICS: The soils are continuously dry in
all parts between depths of 4 and 12 inches for more than 90 consecutive days following the summer solstice. The mean
annual soil temperature is 47 to 52 degrees F. It is mildly
alkaline to moderately alkaline. The particle-size control
section has 10 to 18 percent clay and less than 15 percent
coarser than very fine sand. The mollic epipedon thickness
is 20 to 40 inches thick.

The A horizon has value of 2 or 3 moist and 4 or 5 dry, and
chroma of 2 or 3 moist and dry.

The Bk1 horizon has value of 2 or 3 moist and 4 or 5 dry,
and chroma of 2 or 3 moist and dry. It has weak medium and
coarse prismatic and weak fine to coarse subangular blocky
structure. It is silt loam or very fine sandy loam. It is calcareous throughout.

The Bk2 and Bk3 horizons, to a depth of 40 inches, have
value of 3 or 4 moist and 5 or 6 dry, and chroma of 2 or 3
moist and dry. It is silt loam or very fine sandy loam.
Below a depth of 40 inches the chroma ranges from 1 through
3 and dark reddish brown mottles are typical. The lower
part contains thin lenses of volcanic ash in some pedons.

COMPETING SERIES: These are the Nansene and Ridgedale
series. Nansene and Ridgedale soils lack calcium carbonate accumulations above 40 inches.

GEOGRAPHIC SETTING: Powval soils are on terraces. Slopes
range from 0 to 3 percent. Elevation is 2,200 to 3,500
feet. The soils formed in mixed alluvium with an influence
of volcanic ash. The mean annual temperature ranges from 45
to 49 degrees F. The mean annual precipitation is 9 to 12
inches. The frost-free period is 110 to 140 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Baldock,
Jett, Umapine and Wingville soils. Baldock soils are poorly
drained. Jett soils are fine-silty. Umapine and Wingville
soils are somewhat poorly drained.

DRAINAGE AND PERMEABILITY: Well drained; slow runoff;
moderate permeability. A water table is at 4.0 to 6.0 feet
from February through May.

USE AND VEGETATION: Powval soils are used for irrigated row
crops and small grains, potatoes and alfalfa hay. The
native vegetation is basin wildrye and basin big sagebrush.

DISTRIBUTION AND EXTENT: Eastern Oregon. The series is
inextensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Baker County Area, Oregon; 1988.

REMARKS: Diagnostic horizons and features recognized in
this pedon are:

Mollic epipedon - the zone from the surface of the soil to a
depth of approximately 32 inches (Apk, Ak, Bk1 horizons).


NATIONAL COOPERATIVE SOIL SURVEY
U.S.A.