San Joaquin -- California State Soil

Photograph of landscape of San Joaquin soils showing the hummocky land surface. The hummocks are approximately two to four meters in diameter and one half to one meter in height. Vegetation is grass and forbs.

Photograph of profile of a typifying pedon of San Joaquin soil series.

San Joaquin Soil Profile

Surface layer: brown loam
Subsoil - upper: brown loam
Subsoil - lower: brown clay
Substratum: light brown and brown, indurated duripan with 70 to 90 percent silica-sesquioxide cementation
 California’s Great Central Valley has more than 500,000 acres of San Joaquin soils, named for the south end of that valley. This series is the oldest continuously recognized soil series within the State. It is one of California’s Benchmark Soils, and a profile of it is displayed in the Netherlands World Soil Museum.

The San Joaquin series became the Official State Soil in 1997, the result of efforts by students and teachers from Martin Luther King, Jr. Middle School in Madera, natural resource professionals, the Professional Soil Scientists Association of California, legislators, and various state universities.

These soils are used for irrigated crops, such as wheat, rice, figs, almonds, oranges, and grapes, and for pasture and urban development. San Joaquin soils formed in old alluvium on hummocky topography. A cemented hardpan a few feet beneath the surface restricts roots and water percolation.

Small scale map of California showing distribution of San Joaquin soil series.
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