The Origin of Soils in California

Have you ever wondered where soils come from?  Many of us have come to California from different parts of the country.  We are readily cognizant of differences in the soils "back home" and those found in our new home here in Southern California.  Various soil types have developed around the country because of (1) the chemical composition of centuries old parent material from which soils are formed, and (2) the physical and chemical forces of nature acting on this parent material.  These parental materials are deposited by water, glaciers, wind or gravity into land areas called landforms.  Landforms derived from moving water are alluvial and soils developed in these areas are termed alluvial soil.  Landforms developed from glacial movement and melting ice are called moraines.  Dunes are from wind movement of sand and colluvial landforms are formed by the force of gravity. 

All soils develop from weathered rock, volcanic ash or accumulated plant residues.  Weathered rocks and the minerals such as mica, quartz, feldspar, gypsum, etc. that they yield, generate most of the soils we use.  To us at American Organics, soil is defined as the natural medium for the growth of land plants.  A geologist may term soil as fragmented rock or overburden, whereas an engineer may call soil, earth or rock.  The parent rock which is to become our soil is hardened mass of mineral chemicals such as mica and feldspar as stated above.  The chemical and certain physical properties of our soil is determined by the mineral composition of the parent rock.  For instance, quartz sand used in golf course construction is primarily silicon dioxide.  This mineral appears in many soil types but in aggregation with other substances such as potassium, calcium, aluminum, magnesium, hydroxides, etc.  The nature of the aggregates determines the type of mineral soil and its usefulness to us as topsoil.

Our soils contain sand, silt and clay in varying percentages.  Normally our soils consist of 75-85% sand, 1-10% silt and 5-15% clay.  The rock composition and the action of the environment, such as wind, water movement, volcanic eruptions and freezing/thawing, determines the ultimate sand/silt/clay texture of a soil.  The particle size of sands range from 2.0-0.5mm (millimeters), silt from 0.05-0.002mm and clay below 0.002mm. Soils with high clay content do not drain well and require amendments to increase water penetration.  Similarly, purely mineral soils contain little or no organic matter.  Organic matter in soils originates from numerous biological activities but largely from the microbial degradation of dead plants material.  In Southern California, our soils are low in organic matter because of the dryness of our climate and its negative impact on microbes.

American Organics obtains much of the soil material used in its soil blends locally.  The largest portion of this material is derived from American Organics, Inc. recycling programs which receives organic materials from local cities.  The base material is blended with other soil components to meet the needs of our customers.  Other additives such as sand, wood bark or shavings, and gypsum, etc. are added to provide a suitable structure to the soil which permits good plant support function, drainage and water and mineral holding capacity.

As stated above, the composition of the parent rock and resultant environmental weathering of this material does not always yield a soil suitable for our specific plant growing needs.  For instance, soils in the Victor Valley area have an alkaline pH; that is, they are too basic and they contain too much clay.  The soils do not drain well and consequently, water stands, evaporates from the surface, and deposits salts which renders the soil undesirable for the growth of most plants.  This condition is not always hopeless because at American Organics we are able to supply materials which will improve the chemical and physical properties of soil so that most desired plants can be grown.

Although soils vary throughout our country, some good, some not so good, science has provided us that tools in most cases to render the "not so goods" usable.