LOCATION RIZ CA
Established Series
Rev. SBJ/LCL
01/2023
RIZ SERIES
The Riz series is a member of the fine, montmorillonitic, thermic family of Typic Natrixeralfs. Typically, Riz soils have pale brown and brown, mottled, neutral, silty clay loam A horizons, pale brown and yellowish brown, strongly and very strongly alkaline, silty clay B2t horizons, and light yellowish brown, calcareous, very strongly alkaline C horizons.
TAXONOMIC CLASS: Fine, smectitic, thermic Typic Natrixeralfs
TYPICAL PEDON: Riz silty clay loam - idle (Colors are for dry soil unless otherwise noted.)
Ap--0 to 8 inches; mixed pale brown (10YR 6/3) and brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; common fine distinct strong brown mottles, brown moist; coarse subangular blocky structure; very hard, firm, sticky, plastic; many very fine roots; many very fine pores; the surface inch has weak platy structure and is porous and light gray (2.5Y 7/2); neutral (pH 7.1); abrupt smooth boundary. (6 to 10 inches thick)
B21t--8 to 13 inches; pale brown (10YR 6/3) silty clay, brown (10YR 4/3) moist; weak medium prismatic that parts to coarse angular blocky structure; very hard, very firm, very sticky, plastic; common very fine roots; many very fine pores; thin continuous clay films line pores; strongly alkaline (pH 8.7); clear smooth boundary. (4 to 8 inches thick)
B22t--13 to 23 inches; yellowish brown (10YR 5/4) silty clay, dark yellowish brown (10YR 4/4) moist; angular blocky structure; very hard, very firm, sticky, plastic; few very fine roots; thin continuous clay films line pores; slightly calcareous; very strongly alkaline (pH 9.2); clear wavy boundary. (8 to 15 inches thick)
B3t--23 to 34 inches; yellowish brown (10YR 5/4) silty clay, dark yellowish brown (10YR 4/4) moist; fine subangular blocky structure; hard, firm, sticky, plastic; very few roots; many very fine pores; common thin clay films line pores; common dark manganese stains; weakly calcareous with a few soft white lime concretions; very strongly alkaline (pH 9.5); gradual wavy boundary. (8 to 12 inches thick)
C1--34 to 46 inches; light yellowish brown (10YR 6/4) silty clay loam, yellowish brown (10YR 5/5) moist; very fine subangular blocky structure; hard, friable, sticky, plastic; many very fine pores; few thin clay films line pores; common dark manganese stains; calcareous with lime in common soft white concretions; very strongly alkaline (pH 9.7); gradual wavy boundary. (8 to 20 inches thick)
C2--46 to 60 inches; similar to C1 horizon but strongly calcareous; few soft and hard medium-sized lime concretions; few bluish gray mottles; very strongly alkaline (pH 9.5).
TYPE LOCATION: Glenn County, California; about 6 miles south of Willows; in the NE1/4 of the SE1/4 sec. 9, T.18N., R.3W.
RANGE IN CHARACTERISTICS: Solum thickness is 26 to about 40 inches measured to the base of the B2t horizons. The mean annual soils temperature at a depth of 20 inches ranges from 62 degrees to 65 degrees F. Depth to lime ranges from 10 to 18 inches. The soils are continuously dry between depths of 4 and 12 inches from late May or June until late October or early November. They are moist all the rest of the time. Soils used for growing rice have mottles in the A horizons and upper B2t horizons. Soils not flooded for rice culture do not have mottles above 30 inches but may have mottles below 30 inches. The A horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry and chroma of 3 or 4 moist or dry. It is heavy silty clay loam or clay and contains 5 to 15 percent sand coarser than very fine sand in the average, and 35 to 45 percent clay. This horizon has 15 to 25 percent sodium saturation in all parts. It has weak or moderate prismatic structure in the upper part and subangular blocky or angular blocky structure in the lower part. It is moderately alkaline to very strongly alkaline and weakly to moderately calcareous.
COMPETING SERIES: These are the
Antioch,
Bonsall,
Las Flores,
Lethent, Orestimba,
Pescadero,
Placentia,
Rossi,
San Miguel, and
Stockpen series. Antioch, Las Flores, Placentia, San Miguel, and Stockpen soils have an abrupt AB2t horizon boundary with more than 15 percent clay increase. Bonsall soils have a paralithic contact below the argillic horizon. Lethent soils are moist during part of December, January, and February for less than 90 consecutive days and are dry the rest of the year. Orestimba soils lack natric horizons and lack prismatic structure. Pescadero soils have mottles and chroma of 1 or 2 within 20 inches of the surface. Rossi soils have less than 35 percent clay in the natric horizon.
GEOGRAPHIC SETTING: Riz soils are on smooth, nearly level, lower edges of old alluvial fans that extend into alkali basins. Elevations range from about 10 to 400 feet. The soils formed in strongly calcareous silty sediments. The climate is subhumid mesothermal with hot dry summers and cool moist winters. Mean annual rainfall is 15 to 25 inches. Mean annual temperature is about 60 degrees to 62 degrees F., average January temperature is about 45 degrees F., and average July temperature is about 78 degrees F. Frost-free season is about 250 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Capay,
Clear Lake,
Hillgate,
Myers,
Pescadero, and
Willows soils. Capay, Clear Lake, Myers, and Willows soils have fine textures throughout and lack argillic horizons. Hillgate soils have less than 15 percent exchangeable sodium in the argillic horizons.
DRAINAGE AND PERMEABILITY: Somewhat poorly to poorly drained; slow to very slow runoff; slow to very slow permeability.
USE AND VEGETATION: Used for dry farmed grain and pasture and for rice and irrigated pasture.
DISTRIBUTION AND EXTENT: West side of Sacramento Valley, California where they are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Glenn County, California, 1961.
REMARKS: The Riz soils were formerly classified as Noncalcic Brown soils.
OSED scanned by SSQA. Last revised by state on 6/72.
National Cooperative Soil Survey
U.S.A.