The Riz series consists of poorly drained loams on old terrace remnants. These soils have a subsoil of clay. Slopes are less than 1 percent. The soils formed in alluvium from mixed sources. Elevation ranges from 10 to 30 feet.
Annual temperature is 61° F, annual rainfall is 16 to 18 inches, and the frost-free season is about 280 days. Vegetation is annual grasses, forbs, and perennial grasses that tolerate salt. Riz soils are associated principally with Pescadero and Willows soils.
In a typical profile, the surface layer is light brownish-gray loam about 10 inches thick. The subsoil is mottled, light brownish-gray, brown, and yellowish brown heavy clay loam and clay about 27 inches thick. This is underlain by mottled, light yellowish-brown and yellowish-brown clay loam and loam that extend to a depth of more than 60 inches.
Riz soils are used for rice, irrigated row crops, field crops, and pasture, for dryfarmed small grain, as wildlife habitat, and for recreation.
This soil is on terrace remnants in basin areas. Slopes are less than 1 percent.
Representative profile, 0.2 mile south of Thorpe Road, 0.3 mile east of the Sacramento-Yolo deep water channel, 1.5 miles southwest of West Sacramento; the profile, when examined, was moist below a depth of 14 inches:
Ap-0 to 10 inches, light brownish-gray (2.5Y 6/2) loam; few, fine, prominent mottles of strong brown (7.5YR 5/8), dark grayish brown (10YR 4/2) and few, fine, distinct mottles of yellowish brown (10YR 5/8) when moist; moderate, coarse, prismatic structure; hard, friable, slightly sticky and plastic; common micro and very fine random roots and few fine oblique roots; common micro and very fine vesicular, interstitial and tubular pores; moderately alkaline (pH 8.2); no lime; abrupt, smooth boundary. (9 to 20 inches thick)
B1t-10 to 14 inches, mottled light brownish-gray (2.5Y 6/2), brown (10YR 5/3), and yellowish-brown (10YR 5/6) heavy clay loam, dark grayish brown (10YR 4/2) and common, fine, prominent mottles of yellowish red (5YR 4/6) and common, medium, faint mottles of dark yellowish brown (10YR 4/4) when moist; moderate, coarse, prismatic structure and moderate, coarse, angular blocky structure; hard, friable, sticky and very plastic; common micro and very fine random roots and few fine horizontal roots; common micro and very fine interstitial and tubular pores; few thin clay films on ped faces and in pores; moderately alkaline (pH 8.2); no lime; plentiful manganese shot 1 to 2 millimeters in size; clear, smooth boundary. (0 to 6 inches thick)
B21t-14 to 19 inches, yellowish-brown (10YR 5/4) clay, brown (10YR 4/3) when moist; moderate, coarse, prismatic structure and moderate, coarse, angular blocky structure; very hard, firm, very sticky and very plastic; common micro random roots; common micro interstitial and tubular pores; continuous moderately thick clay films on ped faces and in pores; strongly alkaline (pH 8.6); no lime; plentiful manganese shot 1 to 2 millimeters in size; very dark grayish brown (10YR 3/2) when moist; coatings in very fine and fine old root channels; gradual, wavy boundary. (4 to 10 inches thick)
B22t-19 to 33 inches, yellowish-brown (10YR 5/4) clay brown (10YR 4/3) and few, fine, distinct mottles of strong brown (7.5YR 5/8) when moist; moderate, coarse, prismatic structure and moderate, coarse, angular blocky structure; very hard, firm, very sticky and very plastic; few micro vertical roots; common micro interstitial and tubular pores; continuous moderately thick clay films on ped faces and in pores; strongly alkaline (pH 8.8); slightly effervescent with segregated lime; plentiful manganese shot 1 to 2 millimeters in size; clear, wavy boundary. (10 to 24 inches thick)
B3tca-33 to 37 inches, yellowish-brown (10YR 5/4) clay; common, fine, distinct mottles of strong brown (7.5YR 5/6) and very pale brown (10YR 7/3), dark yellowish brown (10YR 4/4) and common, fine, distinct mottles of strong brown (7.5YR 5/8) when moist; weak, coarse, prismatic structure and moderate, coarse, subangular blocky structure; very hard, firm, very sticky and very plastic; few micro random roots; few micro vesicular and tubular pores; many moderately thick clay films on ped faces and in pores; strongly alkaline (pH 8.6); violently effervescent with lime segregated in filaments up to one-half inch wide throughout the horizon and extends 1 to 4 inches into adjacent horizons; plentiful manganese sot 1 to 2 millimeters in size; clear, irregular boundary. (4 to 8 inches thick)
C1-37 to 44 inches, light yellowish-brown (10YR 6/4) clay loam; common, fine, distinct mottles of dark brown (7.5YR 4/4), dark yellowish brown (10YR 4/4) and common, fine, distinct mottles of dark brown (7.5YR 3/2) when moist; massive; hard, friable, sticky and plastic; few micro random roots; common micro interstitial and tubular pores; common thin clay films in pores; moderately alkaline (pH 8.4); slightly effervescent with disseminated lime and strongly effervescent with lime segregated into filaments; clear wavy boundary. (6 to 14 inches thick)
C2-44 to 69 inches, light yellowish-brown (10YR 6/4) loam; common, fine, distinct mottles of dark brown (7.5YR 4/4), dark yellowish brown (10YR 4/4) and common, fine, prominent mottles of dark reddish brown (5YR ¾) when moist; massive; slightly hard, friable, slightly sticky and plastic; no roots; common fine tubular pores and common micro and very fine interstitial and tubular pores; moderately alkaline (pH 8.4); slightly effervescent and disseminated lime and strongly effervescent with lime segregated into filaments; many manganese or organic stains; numerous concretions of gypsum up to one-half inch in size.
The A horizon ranges in color from light brownish gray to pale brown and in texture from loam to clay loam. This horizon is neutral to moderately alkaline. The B2t horizons range in color from brown to yellowish brown. These horizons are moderately alkaline to strongly alkaline, and the exchangeable sodium percentage ranges from 15 to 20. The C horizons range in color from yellowish brown to light yellowish brown and in texture from loam to heavy clay loam. These horizons are moderately alkaline to strongly alkaline.
Included in mapping are small areas of Capay silty clay, Clear Lake clay, Pescadero silty clay, and Willows clay. Also included are areas where the surface layer is grayish brown or dark grayish brown.
This soil has been improved by open drains, and the water table is now below a depth of 60 inches. Permeability of this Riz soil is very slow. Surface runoff is very slow, and the erosion hazard is none to slight. The available water holding capacity in the rooting depth is 2.0 to 4.0 inches. The effective rooting depth is 26 inches and is limited by the clay subsoil. Natural fertility is low.
This soil is used mainly for rice, grain sorghum, and tomatoes. Other uses include wildlife habitat and recreation. Capability unit is IVw-3, irrigated and non-irrigated.
This soil is similar to Riz loam except that it is subject to flooding at least 1 year out of 3 because of flowage easements. the exchangeable sodium percentage ranges from 15 to 30.
Included in mapping are areas of Clear Lake soils, flooded; Pescadero soils, flooded; and Willows soils, flooded.
This Riz soil is subject to deposition.
This soil is a part of the Yolo By-Pass and is used mainly for rice and grain sorghum. Other uses include wildlife habitat and recreation. Capability unit IVw-3, irrigated and non-irrigated.