LOCATION LAMONTA OR+IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Abruptic Argiduridic Durixerolls
TYPICAL PEDON: Lamonta gravelly loam, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 7 inches; grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak thin platy and weak fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine irregular pores; few pale brown sand size pumice fragments and 25 percent gravel; neutral (pH 6.8); clear smooth boundary. (6 to 10 inches thick)
BAt--7 to 9 inches; brown (10YR 5/3) gravelly loam, dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; hard, firm, sticky and plastic; common very fine roots; many very fine tubular pores; few faint patchy clay films; 25 percent gravel; neutral (pH 6.6); abrupt wavy boundary. (0 to 6 inches thick)
2Bt1--9 to 20 inches; brown (10YR 5/3) cobbly clay, dark brown (10YR 3/3) moist; strong medium prismatic structure parting to moderate fine and medium blocky; very hard, very firm, very sticky and very plastic; continuous prominent clay films or pressure faces on surfaces of peds; few very fine tubular pores; few very fine roots between peds; 20 percent cobbles and 10 percent gravel; neutral (pH 7.1); clear wavy boundary. (4 to 11 inches thick)
2Bt2--20 to 23 inches; yellowish brown (10YR 5/4) cobbly clay, dark yellowish brown (10YR 4/4) moist; moderate medium blocky structure; very hard, very firm, very sticky and very plastic; common prominent clay films or pressure faces; 20 percent cobbles and 10 percent gravel; mildly alkaline (pH 7.6); weakly calcareous; abrupt smooth boundary. (0 to 5 inches thick)
3Bkqm--23 inches; pale brown (10YR 6/3) indurated, silica-cemented gravelly hardpan; massive or thick platy structure; thin indurated laminar capping of silica; lime in seams; common black stains; moderately alkaline (pH 8.2).
TYPE LOCATION: Crook County, Oregon; in the NW1/4 NE1/4 SW1/4 section 32, T. 13 S., R. 15 E.
RANGE IN CHARACTERISTICS: The soils are dry in all parts of the soil above 12 inches for at least half the time (cumulative) during the periods the soil temperature is about 41 degrees F., and dry for more than 60 consecutive days between depths of 4 and 12 inches within the three-month period following the summer solstice. The mean annual soil temperature is 48 to 52 degrees F. Depth to the duripan ranges from 20 to 30 inches. Depth to bedrock is over 60 inches.
The A horizon has value of 4 or 5 dry and chroma of 2 or 3 moist and dry. It is loam, gravelly loam, cobbly loam, stony loam, or cobbly clay loam.
The 2Bt horizon has value of 5 or 6 dry and 3 or 4 moist and chroma of 3 or 4 dry and 2 through 4 moist. It is cobbly clay or clay. The upper part has moderate medium prismatic to strong or moderate fine and medium blocky structure. The lower part has weak or moderate structure and is calcareous in some pedons.
The 3Bkqm horizon (duripan) is indurated in the upper part and ranges to strongly or weakly cemented in the lower part. It is massive or platy and more than half the surface has a laminar coating.
COMPETING SERIES: There are no established competing series.
GEOGRAPHIC SETTING: Lamonta soils are on terraces, pediments, and plateaus at elevations of 2,200 to 3,300 feet in Oregon and up to 4,900 feet in Idaho. Slopes are 0 to 20 percent. They formed in old alluvium, residuum, and colluvium of sedimentary origin. The climate is characterized by cool moist winters and hot dry summers. The mean winter temperature is 32 to 36 degrees F., mean summer temperature is 62 to 64 degrees F., and mean annual temperature is 46 to 50 degrees F. The mean annual precipitation is 9 to 13 inches. The frost-free period is 50 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Court, Era, Madras, McCoin and Metolius soils. Court and Era soils are moderately coarse and medium textured and lack argillic horizons and duripans. Madras soils have loam to clay loam argillic horizons. McCoin soils lack duripans and have clay loam cambic horizons. Metolius soils lack a duripan.
DRAINAGE AND PERMEABILITY: Well drained, very slow permeability.
USE AND VEGETATION: These soils are used primarily for pasture. Other uses are for growing small grain and for livestock grazing, wildlife habitat, and water supply purposes. Native vegetation is bluebunch wheatgrass, sandberg bluegrass, Idaho fescue, antelope bitterbrush, big sagebrush, western yarrow, and lomatium.
DISTRIBUTION AND EXTENT: East-central Oregon and southern Idaho; MLRA 10, 25. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Deschutes Irrigation Project, Oregon, 1946.
REMARKS: Diagnostic horizons and features in this pedon include:
Mollic epipedon - from 0 to 9 inches (Ap and BAt horizon).
Argillic horizon - from 9 to 23 inches (2Bt1 and 2Bt2 horizons).
Duripan - 23 inches (3Bkqm)
Abruptic feature - 20 percent increase (absolute) in clay from BAt to 2Bt1 horizon.
Aridic soil moisture regime.
Particle-size control section - from 9 to 23 inches.
NSTH 17, RECLASSIFICATION ONLY, 3/95