CA State Soil

We all know California has many state symbols. The grizzly bear flying in the state flag, golden poppies and the valley quail are all symbols that connect you back to our golden state. Did you know that California has a state soil?

What is a State Soil?

A state soil is a soil that has special significance to a particular state. Each state in the United States has selected a state soil, twenty of which have been legislatively established. These “Official State Soils” share the same level of distinction as official state flowers and birds. Also, representative soils have been selected for Puerto Rico and the Virgin Islands. California’s State Soil is the “San Joaquin” soil. It was designated the official state soil of California in 1997. California’s central valley has more than half a million acres of San Joaquin soils.

A little about soil profiles and textures

Soil Horizons

Soil is made up of distinct layers, called horizons. Each layer has its own characteristics that make it different from all of the other layers. These characteristics play a very important role in what the soil is used for and why it is important.

O HORIZON- This is the top layer of soil that is made up of living and decomposed materials like leaves, plants, and bugs. This layer is very thin and is usually pretty dark.

A HORIZON- This is the layer that we call “topsoil” and it is located just below the O Horizon. This layer is made up of minerals and decomposed organic matter and it is also very dark in color. This is the layer that many plants roots grow in.

B HORIZON- This is the layer that we call “subsoil” and it is located just below the A Horizon. This layer has clay and mineral deposits and less organic materials than the layers above it. This layer is also lighter in color than the layers above it.

C HORIZON- This is the layer that we call “regolith” and it is located just below the B Horizon. This layer is made up of slightly unbroken rock and only a little bit of organic material is found here. Plant roots are not found in this layer.

Soil Textures

Three types of particles are found in soil: sand, silt and clay. Soil texture is classified by the type of particle that makes up the majority of the soil. Each soil type has a distinctive textural feel and holding a sample of your garden soil in your hand may help you determine the type of texture that makes up your garden soil.

Sandy Soil: Sand is the largest of the particles found in soil. It is a sharp-edged material, giving the soil a gritty feel. When wet, it remains course and breaks apart easily. Beach sand is at the extreme end of sandy soils. Sandy soil holds almost no nutrients and does not retain moisture. Plants do not grow well in this type of soil.

Silty Soil:  Silt particles are smooth and smaller than sand particles. When wet, a silty soil feels mud-like; it’s smooth and has a silky texture. It’s rich in nutrients but retains moisture to the point where garden plants are unable to access oxygen. In a silty soil, plants wilt because they can’t breathe.

Clay Soil: Clay is the smallest of the particles and a clay soil will clump and feel sticky when wet. Air flow between particles is limited if not non-existent. When dry, the soil has a dusty feel to it and the surface is hard and dense, making it difficult to work the soil for tilling or digging. Although high in nutrients, clay soil is less than ideal for gardens. Plant roots may not be able to penetrate the dense soils to access nutrients and oxygen.

Loamy Soil: Loam is a combination of all three particles– sand, silt and clay–in nearly-equal proportions. The large sand particles promote drainage and air flow within the soil. The smaller silt particles are rich in nutrients and aid in moisture retention. Clay, also rich in nutrients, balances the poor soil retention of the sand and the excessive moisture of the silt.

If you would like to see what kind of soil you have, click here to start NRCS’s web soil survey.

If you are curious to see all of California’s state symbols from fish to gemstone, click here.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website.

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  • Blog Author

    Marcy Sousa

    Marcy Sousa is the San Joaquin County UC Master Gardener Program Coordinator. She is a Stockton native and enjoys teaching others about gardening. She has her bachelors from Stanislaus State in Permaculture. She has been with the program since 2007. Read Full
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