LOCATION LORNA                   AZ

Established Series
HAH/JMH/NMS
02/2025

LORNA SERIES

The Lorna series consists of moderately deep, well drained soils formed in alluvium over residuum derived from sandstone, siltstone or mudstone. Lorna soils are on back slopes and foot slopes of structural benches along remnant mesas. Slopes range from 8 to 35 percent. The mean annual precipitation is about 14 inches and the mean annual temperature is about 54 degrees F.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Ustic Calciargids

TYPICAL PEDON: Coarse-loamy - rangeland. (Colors are for dry soil unless otherwise noted.)

A--0 to 3 inches (0 to 8 cm); reddish brown (2.5YR 5/4) gravelly sandy loam, reddish brown (2.5YR 4/4), moist; 18 percent clay; weak very fine granular structure; soft, loose, slightly sticky, slightly plastic; common very fine roots throughout and common fine roots throughout; many very fine irregular pores; 20 percent gravel and 4 percent channer; strongly effervescent; moderately alkaline, pH 8.4; gradual smooth boundary.

Bt--3 to 10 inches (8 to 25 cm); reddish brown (2.5YR 4/4) gravelly sandy clay loam, dark reddish brown (2.5YR 3/4), moist; 34 percent clay; moderate medium angular blocky structure; slightly hard, very friable, moderately sticky, moderately plastic; common very fine roots throughout and common fine roots throughout; many very fine irregular pores; few faint clay films on surfaces along pores; 20 percent gravel and 10 percent channer; violently effervescent; moderately alkaline, pH 8.4; clear smooth boundary.

Btk--10 to 21.5 inches (25 to 54 cm); reddish brown (2.5YR 4/4) gravelly sandy clay loam, dark reddish brown (2.5YR 3/4), moist; 30 percent clay; moderate medium subangular blocky structure; moderately hard, friable, moderately sticky, moderately plastic; common very fine roots throughout; many very fine dendritic tubular pores; few distinct clay films on surfaces along pores; and many carbonate masses in matrix; 25 percent gravel and 5 percent channer; violently effervescent; strongly alkaline, pH 8.6; clear smooth boundary.

Bk--21.5 to 37.5 inches (54 to 95 cm); yellowish red (5YR 5/6) very gravelly sandy clay loam, light reddish brown (5YR 6/3), moist; 25 percent clay; moderate fine subangular blocky structure; moderately hard, friable, moderately sticky, moderately plastic; few very fine roots throughout; many very fine dendritic tubular pores; common carbonate laminae around rock fragments and many fine irregular weakly cemented carbonate masses in matrix; 25 percent gravel and 10 percent channer; violently effervescent; strongly alkaline, pH 8.6; clear smooth boundary.

Cr--37.5 to 40 inches (95 to 101 cm); fractured, weathered shale bedrock.

R--40 to 49.5 inches (101 to 126 cm); unfractured, unweathered sandstone bedrock.

TYPE LOCATION: Coconino County, Arizona, about five miles west of Cedar Ridge, Arizona, along foot slopes of Broadway Mesa on the Navajo Reservation. Geographic Coordinate System: 36 21' 33.00'' North, 111 36' 19.90'' West

RANGE IN CHARACTERISTICS:
Soil moisture: Intermittently moist in the SMCS in some parts of July-September and December-February. Ustic aridic moisture regime.
Depth to Cr horizon 37 inches (95cm)
Rock fragments of the control section: 10 to 40 percent gravels and channers.

Particle-size control section clay content: 18 to 35 percent

A Horizon
Hue: 2.5YR, 5YR
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 4 to 6, dry or moist
Texture: fine sandy loam, sandy loam, gravelly sandy clay loam
Clay: 15 to 20 percent
Calcium carbonate equivalent: 0 to 4 percent
Rock fragments: 20 to 40 percent gravels
Reaction: moderately alkaline

Bt Horizon
Hue: 2.5YR, 5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 to 6, dry or moist
Texture: fine sandy loam, sandy loam, sandy clay loam, gravelly sandy clay loam
Clay: 25 to 35 percent
Calcium carbonate equivalent: 0 to 15 percent
Rock fragments: 15 to 40 percent gravels and cobbles
Reaction: moderately alkaline

Btk Horizon
Hue: 2.5YR, 5YR
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry or moist
Texture: fine sandy loam, sandy loam, sandy clay loam, very gravelly sandy clay loam
Clay: 25 to 35 percent
Calcium carbonate equivalent: 5 to 15 percent
SAR: 0 to 4
Rock fragments: 20 to 40 percent gravels and channers
Reaction: strongly alkaline

Bk Horizons
Hue: 2.5YR, 5YR
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry or moist
Texture: loam, sandy loam, sandy clay loam, gravelly sandy clay loam
Clay: 20 to 30 percent
Calcium carbonate equivalent: 5 to 15 percent
SAR: 0 to 4
Rock fragments: 20 to 40 percent gravels and channers
Reaction: strongly alkaline

Diagnostic Feature(s):
Ochric Epipedon- 0 to 1.5 inches (0 to 4 cm).
Argillic Horizon- 3 to 21.5 inches (8 to 54 cm).
Calcic Horizon- 10 to 37.5 inches (25 to 95 cm).

COMPETING SERIES: These are the Balon, Barx, Bowbac, Buckle, Cambria, Cerrillos, Clovis, Cushman, Fattig, Fernando, Decolney, Flaco, Forkwood, Fort Collins, Gaddes, Gapbutte(T), Hagerman, Harbord, Hiland, Los Alamos, Maysdorf, Millet, Oelop, Olney, Palacid, Penistaja, Pokeman, Potts, Pugsley, Scholle, Spangler, Spenlo, Stoneham, Sundance, Tapia, Threetop, Toluca, Tuweep, and Yenlo series. Balon, Barx, Bowbac, Buckle, Cambria, Cerrillos, Clovis, Decolney, Fernando, Forkwood, Fort Collins, Gaddes, Harbord, Hiland, Los Alamos, Maysdorf, Millett, Oelop, Olney, Palacid, Penistaja, Pokeman, Potts, Pugsley, Scholle, Spenlo, Stoneham, Tapia, Toluca, Tuweep, and Yenlo soils lack lithic contacts within depths of 40 inches. Cushman and Hagerman soils lack a calcic horizon below the argillic horizon. Fattig soils have chroma of 1 in the Bt horizon. Flaco soils have mean annual soil temperatures greater than 52 degrees F. Gapbutte soils have less than 15 percent calcium carbonate equivalent. Spangler soils have a paralithic contact above depths of 40 inches. Sundance soils have lithologic discontinuities. Threetop soils have soil moisture control sections that are moist in some or all parts in May and June.

GEOGRAPHIC SETTING: Lorna soils are on structural benches, along remnant mesas and old terraces. The soil formed in alluvium and colluvium derived from sandstone, mudstone or siltstone. Slopes range from 8 to 35 percent. Elevation ranges from 5,300 to 6,800 feet. The mean annual precipitation ranges from 10 to 14 inches occurring as summer thunderstorms and as winter rain and snow. Mean annual air temperature is about 54 degrees F., the mean annual precipitation is 10 to 14 inches, and the average frost-free period ranges from 120 to 180 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the, Barx soils, and Pinon soils. Pinon soils have hard bedrock at depths above 20 inches.

DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

USE AND VEGETATION: This soil is used mainly for rangeland. Native vegetation consists mainly of blue gramma, Indian rice grass, needle and thread, spike drop seed, winter fat, juniper, pinion, cliff rose, skunk bush sumac and broom snake weed.

DISTRIBUTION AND EXTENT: Northern Arizona. The series is moderately extensive. MLRA 35.

SERIES ESTABLISHED: Little Colorado River Area, AZ, Parts of Coconino and Navajo Counties

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 3 inches
Argillic horizon - the zone from 3 to 21 inches.
Calcic horizon - the zone from 21 to 37 inches
Lithic contact - the boundary with sandstone at 40 inches.
Classified according to Soil Taxonomy Twelfth Edition, 2014
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National Cooperative Soil Survey
U.S.A.