LOCATION RIVEROAD                AZ

Established Series
Rev. CCC/PDC
04/2011

RIVEROAD SERIES

The Riveroad series consists of very deep, well drained soils formed in stream alluvium from mixed sources. Riveroad soils are on flood plains and alluvial fans and have slopes of 0 to 5 percent. The mean annual precipitation is about 14 inches and the mean annual air temperature is about 65 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, thermic Ustic Torrifluvents

TYPICAL PEDON: Riveroad clay loam - rangeland. (Colors are for dry soil unless otherwise noted.)

A--0 to 4 inches; brown (10YR 5/3) stratified clay loam, dark brown (10YR 3/3) moist; weak thick platy structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine roots; common very fine irregular pores; common thin sand coatings on faces of peds; thick (4 cm) pale brown (10YR 6/3) finely stratified silt loam and very fine sandy loam layer on the surface, brown (10YR 4/3) moist; slightly alkaline (pH 7.4); abrupt smooth boundary. (2 to 13 inches thick)

C1--4 to 21 inches; brown (10YR 4/3) clay loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; many very fine irregular pores; few thin very fine sand coatings on faces of peds; slightly effervescent, few fine filaments of calcium carbonate in pores; slightly alkaline (pH 7.4); clear wavy boundary. (12 to 20 inches thick)

C2--21 to 33 inches; dark grayish brown (10YR 4/2) clay loam, very dark brown (10YR 2/2) moist; weak medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; common very fine tubular pores; slightly alkaline (pH 7.4); clear wavy boundary. (6 to 15 inches thick)

C3--33 to 60 inches; brown (7.5YR 4/4) clay loam, dark yellowish brown (10YR 3/4) moist; moderate medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; few very fine roots; common fine tubular pores; slightly effervescent, few fine filaments of calcium carbonate in pores; common faint organic stains on faces of peds and lining pores; slightly alkaline (pH 7.4).

TYPE LOCATION: Pima County, Arizona; 1660 feet south and 200 feet east of the northwest corner of section 26, T. 18 S., R. 9 E.

RANGE IN CHARACTERISTICS:

Soil moisture - Intermittently moist in some part of the soil moisture control section during December-March and July-September. Driest during May and June. The epipedon is moist in some part less than 90 days (cumulative) when the soil temperature is above 41 degrees F. in 7 out of 10 years. Ustic aridic soil moisture regime.

Soil temperature: 62 to 72 degrees F.

Rock fragments: 0 to 15 percent gravel

Texture: averages less than 15 percent fine sand or coarser. Averages 5 to 40 percent very fine sand and l8 to 35 percent clay in the control section

Organic matter: 1 to 5 percent decreasing irregularly with depth

Reaction: neutral to moderately alkaline

Stratification: commonly stratified with finer or coarser material throughout

Gypsum content: 0 to 4 percent

A and C horizons
Hue: 10YR, 7.5YR
Value: 3 through 6 dry, 2 through 5 moist
Chroma: 1 through 4, dry or moist
Texture: loam, silt loam, silty clay loam, clay loam, silty clay

COMPETING SERIES: These are the Crowflats (NM) and Nillo (TX) series. Crowflats soils are dominantly silt loam and very fine sandy loam in the control section and have mean annual precipitation of 8 to 10 inches. Nillo soils have buried palesols and are formed in tuff parent material from the Duff and Pruett Formations.

GEOGRAPHIC SETTING: Riveroad soils are on flood plains and alluvial fans with slopes of 0 to 5 percent. They formed in stratified stream alluvium from metamorphic, sedimentary and basic and acid igneous rock. Elevation ranges from 2,200 to 4,950 feet. Mean annual precipitation is 12 to 16 inches occurring as summer thunderstorms and winter rain. Mean annual air temperature is 60 to 70 degrees F. The frost-free period is about 180 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bodecker, Comoro, Guest, Hayhook, Sonoita, and Ubik soils. Bodecker soils are sandy-skeletal. Hayhook, Comoro, Sonoita, and Ubik soils are coarse-loamy. Guest soils are fine.

DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate to moderately slow permeability. This soil is subject to flooding.

USE AND VEGETATION: Used for livestock grazing, irrigated cropland and urban development. Vegetation is mesquite, sacaton, vine mesquite, grama grasses, cane beardgrass, and catclaw. Irrigated crops include cotton, sorghum, wheat, alfalfa, sugar beets, lettuce and small grains.

DISTRIBUTION AND EXTENT: Southern Arizona. The Riveroad soils are moderately extensive. This soil occurs in LRR-D, MLRAs 40 and 41.

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

SERIES ESTABLISHED: Pima County, Arizona; Soil survey of Pima County, Arizona, Eastern Part; 1986.

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

Ochric epipedon - the zone from 0 to 4 inches (A horizon)

Entisol feature - the absence of diagnostic subsurface horizons

Fluvial feature - irregular decrease in organic carbon in the zone from 4 to 60 inches (C1, C2, C3, C4 horizons)

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010

Updated competing series sectiom, 4/10/2008, CEM

Revised for the correlation of Graham County, AZ, Southwestern Part; March, 2011, WWJ

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National Cooperative Soil Survey
U.S.A.