LOCATION ROUNDTOP AZ

Established Series
Rev. WRM/JEJ/YHH
12/2022

ROUNDTOP SERIES

The Roundtop soils consist of moderately deep, well drained, slowly permeable soils formed in residuum from cherty limestone and limestone with some local influence from quartzite. Roundtop soils are on gently sloping to moderately steep plains. Slopes range from 2 to 30 percent. Mean annual precipitation is about 17 inches, and mean annual temperature is about 53 degrees F.

TAXONOMIC CLASS: Fine, mixed, superactive, mesic Aridic Argiustolls

TYPICAL PEDON: Roundtop gravelly clay loam - rangeland (Colors for dry conditions unless otherwise noted)

A--0 to 3 inches; dark reddish gray (5YR 4/2) gravelly clay loam, dark reddish brown (5YR 3/2) moist; moderate fine granular structure; soft friable, slightly sticky and slightly plastic; plentiful fine roots; many fine interstitial pores; noneffervescent; neutral (pH 7.0); clear smooth boundary. (2 to 4 inches thick).

Bt1--3 to 8 inches; reddish brown (5YR 4/3) gravelly heavy clay loam, dark reddish brown (5YR 3/3) moist; weak medium subangular blocky breaking to weak fine granular structure; slightly hard, friable, sticky and plastic; plentiful fine and very fine roots; common fine interstitial pores; few thin clay films on ped faces and in pores; noneffervescent; neutral (pH 7.0); gradual wavy boundary. (0 to 7 inches thick.)

Bt2--8 to 15 inches; reddish brown (5YR 4/3) gravelly clay, dark reddish brown (5YR 3/3) moist; moderate medium angular blocky structure; very hard, firm, sticky and very plastic; plentiful very fine and few coarse roots; few fine interstitial and tubular pores; many moderately thick clay films on ped faces and in pores; slightly effervescent; slightly alkaline (pH 7.5); gradual wavy boundary. (5 to 10 inches thick).

Bt3--15 to 23 inches; reddish brown (5YR 4/4) gravelly clay, dark reddish brown (5YR 3/4) moist; strong medium angular blocky structure; very hard, firm, sticky and very plastic; plentiful very fine and few coarse roots; few fine interstitial and tubular pores; many moderately thick clay films on ped faces and in pores; strongly effervescent; slightly alkaline (pH 7.5); gradual wavy boundary. (8 to 12 inches thick.)

Btk--23 to 36 inches; reddish brown (5YR 5/4) gravelly heavy clay loam, reddish brown (5YR 4/4) moist; common pinkish white (5YR 8/2) lime mottles and segregations, pinkish gray (5YR 7/2) moist; weak medium subangular blocky structure; slightly hard, firm, sticky and plastic; few very fine and coarse roots; few fine tubular and interstitial pores; few thin clay films line pores; violently effervescent; moderately alkaline (pH 8.0); abrupt irregular boundary. (5 to 13 inches thick.)

R--36 to 40 inches; grayish brown (10YR 5/2) fractured cherty limestone, dark grayish brown (10YR 4/2) moist; massive; extremely hard.

TYPE LOCATION: SE1/4 of Sec. 26, T7N, R16E, Fort Apache Indian Reservation, Gila County, Arizona. (Note: County is unsurveyed. Location is approximate and based on extended grid from surveyed areas.)

RANGE IN CHARACTERISTICS:

Depth to bedrock: 20 to 40 inches

Depth to the Btk horizon: 15 to 38 inches

Soil moisture: These soils are dry for 90 cumulative days or more in most years in some subhorizon of the soil between 7 and 20 inches, but are not continuously dry in all parts of the soil between these depths for as long as 60 consecutive days in more than 7 out of 10 years. Aridic ustic moisture regime.

Reaction: neutral to moderately alkaline

Mean annual soil temperature; 48 degrees F. to 56 degrees F.

A1 horizon
Hue: 5YR thru 10YR
Value: 4 and 5 dry and 2 and 3 moist
Chroma: 2 and 3
Texture: loam, silt loam, gravelly silt loam, very fine sandy loam, gravelly loam, clay loam, gravelly clay loam and cobbly clay loam.

upper B horizon
Hue: 5YR and 7.5YR
Value: 4 and 5 dry and 3 moist
Chroma: 2 and 3
Texture: clay loam, gravelly clay loam, cobbly clay loam, clay, gravelly clay and cobbly clay.

lower Bt horizons
Hue: 5YR and 2.5YR
Value: 4 and 5 dry and 3 and 4 moist
Chroma: 3 thru 6
Texture: clay loam, gravelly clay loam, cobbly clay loam, clay, gravelly clay and cobbly clay.

A Ck horizon may occur between the B3tca and R horizon.

COMPETING SERIES: These are the Abrazo (NM), Cantina (NM), Carnero (NM), Celsosprings (NM), Charette (NM), Concho (NM), Cueva (NM), Judd (NM), Remunda (NM), Rond (AZ) and Philmont(NM) series. Abrazo soils have a lithic contact of igneous bedrock at 27 inches. Carnero soils have a lithic contact of sandstone at 28 inches. Cueva soils have a paralithic contact of sandstone and shale at 33 inches. Celsosprings, Charette, Concho, Judd, Remunda and Philmontsoils are very deep. Cantina and Rond soils are deep. The Rond series was created to be the deeper counterpart to the Roundtop series.

GEOGRAPHIC SETTING: The Roundtop soils are on gently sloping to moderately steep plains. Slopes range from 2 to 30 percent. These soils are formed in place in residuum from cherty limestone and limestone with some local influence from quartzite. Elevations range from 4500 to 6000 feet. The average annual precipitation ranges from 14 to 20 inches, the mean annual temperature ranges from 48 degrees F. to 58 degrees F. The frost-free season ranges from 120 to 170 days.

GEOGRAPHICALLY ASSOCIATED SOILS: In addition to the Rond, Showlow, Dye and Jacks series these include the Lynx and Tortugas series. Lynx and Tortugas soils are dark-colored and lack argillic horizons. Tortugas soils are shallow to bedrock

DRAINAGE AND PERMEABILITY: These soils are well-drained. Runoff is medium and permeability is slow.

USE AND VEGETATION: Used for grazing of livestock. Native vegetation includes pinon pine, juniper, oak, blue grama, bear grass, mountain mahogany, ring muhly, sideoats grama and snakeweed with ponderosa pine at the higher elevations.

DISTRIBUTION AND EXTENT: Eastern Gila County, Arizona and possibly Navajo and Apache Counties. The series is extensive. MLRA 39.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Fort Apache Indian Reservation, Gila Co., Arizona, 1971. Name is from a local mountain in Gila County, Arizona.

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

Mollic epipedon: The zone from 0 to 15 inches. (A, Bt1, Bt2 horizons)

Argillic horizon: The zone from 3 to 23 inches. (Bt1, Bt2, Bt3 horizons)

Classified according to Keys to Soil Taxonomy Tenth Edition, 2006.

Classification changed to Aridic subgroup in 2007. The change was made to be consistent with the moisture regime.

National Cooperative Soil Survey
U.S.A.