LOCATION TRIGO              CA
Established Series


The Trigo series consists of shallow, well drained soils formed in consolidated alluvium from mixed sources on dissected terraces. Slopes are 2 to 60 percent. The mean annual precipitation is about 10 inches and the mean annual temperature is about 61 degrees F.

TAXONOMIC CLASS: Loamy, mixed, superactive, nonacid, thermic, shallow Typic Xerorthents

TYPICAL PEDON: Trigo fine sandy loam, under annual grasses and forbs. (Colors are for dry soil unless otherwise noted.)

A--0 to 3 inches; pale brown (10YR 6/3) fine sandy loam; brown (10YR 4/3) moist; massive; slightly hard, friable; slightly sticky and slightly plastic, many very fine roots; many very fine tubular pores; slightly acid (pH 6.5); clear smooth boundary. 1 to 14 inches thick.

C--3 to 16 inches; pale brown (10YR 6/3) loam; brown (10YR 5/3) moist; massive; friable; slightly sticky and slightly plastic; common very fine roots; common very fine pores; slightly acid (pH 6.1); clear smooth boundary. 0 to 15 inches thick.

Cr--16 to 20 inches; white (10YR 8/2) softly consolidated stratified fine sandy alluvial sediments with a few lime seams in places, light gray (10YR 7/2) moist; firm when moist, does not slake in water.

TYPE LOCATION: Madera Area, Madera County, California. Southeast 1/4 of Section 14, T. 11 S., R. 19 E. About 10 miles east of Madera.

RANGE IN CHARACTERISTICS: The soil is shallow to consolidated sediments. Depth is 6 to 20 inches. The mean annual soil temperature is 59 to 65 degrees F. The soil is moist for about 100 days when the soil temperature is above 41 degrees F.

The A horizon is 2.5Y or 10YR 5/2, 5/3, 6/2, 6/3 or 7/2 dry, and 2.5Y or 10YR 3/3, 4/2, 4/3, 4/4 or 5/2 dry. Reaction is slightly acid or neutral. The particle size control section is 8 to 18 percent clay.

The C horizon is 2.5Y or 10YR 5/3, 6/2, 6/3, 6/4 or 7/2. Moist color is 2.5Y or 10YR 4/2, 4/3. 5/2, 5/4 or 6/4. Reaction is slightly acid to slightly alkaline. Some areas have a few lime seams and are slightly effervescent in the lower part.

COMPETING SERIES: These are the Cieneba, Borreguero (T), and Gillender series. Cieneba soils weathered from granitic rock and have 15 to 25 percent coarse and very coarse sand. Borreguero soils have a B horizon and more than 18 percent clay. Gillender soils are very shallow and moderately well drained.

GEOGRAPHIC SETTING: Trigo soils are on dissected fan terraces. The soils formed in consolidated sediments mainly from silty or fine sandy alluvium. Slopes are 2 to 60 percent. Elevations are 200 to 2,000 feet in a semiarid mesothermal climate. Precipitation is 8 to 12 inches with warm dry summers and cool somewhat moist winters. The average January temperature is 45 degrees F.; an average July temperature 81 degrees F. The mean annual temperature is 58 to 64 degrees F. The frost free season is 225 to 300 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chanac soils. Chanac soils are very deep and fine-loamy.

DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; Moderately rapid permeability.

USE AND VEGETATION: Mainly annual grasses; red brome, wild oats, ripgut brome, filaree, foxtail fescue and mouse barley.

DISTRIBUTION AND EXTENT: The central and southern parts of the San Joaquin Valley. The soil is not extensive in MLRA 17.


SERIES ESTABLISHED: Madera Area, Madera County, California, 1959.

REMARKS: OSED previous revision was in 1959.

National Cooperative Soil Survey