Did you know that there is a state ground, just like the state flower (the poppy) and the state animal (the bear)? Yes, the soil in the state of California is called “San Joaquin” soil and was officially designated as such in 1997. The Central Valley has over one million acres of “San Joaquin” soil. This is not surprising as our main export from the valley is food and other agricultural products. But I’m sure the land appreciates being recognized for its importance to California’s well-being.
Soil (please don’t call it earth) is a complex world made up of organic matter like insects and worms and decaying plants, minerals of various sizes (more on this important feature later), air and water. In this article, I would like to talk about this vital part of the garden. I take some of my information from the excellent book The Home Orchard by C. Ingels, P. Geisel and M. Norton, published by the University of California. It is highly recommended for people who have deciduous fruit and nut trees (i.e. they lose their leaves in the fall). It is one of the books often used by master gardeners to educate the public and in their own orchards. I also refer those interested in this and other gardening topics to the Integrated Pest Management site (http://ipm.ucanr.edu/) maintained by the University of California for Agriculture and Natural Resources. This site is a mine of information on all things gardening.
The ground is made up of layers called Horizons, each with unique characteristics that differ from the others. The upper horizon is called the topsoil. This soil is usually dark and is made up of living things like insects and worms, fungi and bacteria that co-exist with plants and can most often help them. It also contains decaying organic matter that nourishes the plant. Topsoil is not very deep, several inches to a few feet, and is home to the majority of plant roots. Beneath the topsoil is the subsoil horizon which accumulates leached clay particles, minerals and salts. It contains less organic matter and houses the deep roots of plants like trees. The lowest horizon is called the regolith and is made up of rocks and has little organic matter available. The roots are not in this layer. So in your gardening, unless there has been deep plowing or digging that has disturbed these horizons, topsoil is what you should be working with.
Soil minerals are defined by their size. Sand particles are large enough to be seen with the naked eye. Silt particles are considered “medium” in size and are too small to see individually. Clay particles are so small that they can only be seen under a microscope. The texture of a soil is made up of the relative proportions of these three quantities. Soil scientists have defined 12 types of textures and put them in a diagram that gives relative percentages of different particles. This complex image is a start for people concerned with understanding soil types, but an easier way that anyone can learn and use is called the “feel test” for soil texture. There are many resources on how to do this test, but for those who are “visual learners”, like me, I will refer to the great You-tube video from Kansas State University Research and Extension: https:// www.youtube.com com/watch?v=UKT9RBIkeKc
This video will show you how to test your soil for a rough estimate of soil texture and is also great if you fancy playing in the mud.
Soil can present many physical and chemical problems. A major topic is the pH, ie the degree of acidity or alkalinity of the soil. An inexpensive kit for testing pH is widely available at most nurseries and home improvement centers. It offers simple tests for pH, nitrogen, phosphorus and potassium. Advisors Jim Downer and Ben Faber of Ventura County Extension tested five commercially available kits against results obtained by UC Davis Analytical Laboratory. The results are described in their article (https://ucanr.edu/sites/ucceventura/files/35923.pdf), but the bottom line is that home test kits such as Rapidtest™ are easy to use and are more 90% correct.
The soil may also have an excess of salts and elements like sodium, boron or chloride. There are soil labs in our area that can give a more complete analysis. If you really want to know the details of your soil composition, call your local California Extension office for a referral. If you have soil that is impossible to amend or contaminated with chemicals, you can still have healthy plants by putting them in raised beds.
So be good to your state soil here in the San Joaquin Valley by testing, amending with compost if necessary, and using mulch to retain moisture and reduce weeds.
Master Gardeners will be available to answer your questions in a few select locations over the next few months!
Visalia Farmer’s Market – 1st and 3rd Saturday, 8 a.m. to 11 a.m., 2100 W. Caldwell Ave (behind Sears)
Hanford Farmers Market – 4th Thursday – 5-9pm
Call us: Master Gardeners in Tulare County: (559) 684-3325, Tuesday and Thursday, 9:30-11:30 a.m.; Kings County: (559) 852-2736, Thursdays only, 9:30 a.m. to 11:30 a.m.
Instagram at: @mgtularekings
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