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Tutorial on soils

Soils 101 
A Necessary Primer

(but don't dismiss soil as mere "dirt")

The person who commented about soil, "You just gotta love it," was wiser than he or she perhaps thought.

     Not only do we NEED to love the soil, we need to care for it, to nourish it, and depending on how emotional or, frankly, spiritual, we want to get, to understand that our very
existance depends on the vigor and health of our soil. 
    
     We acknowledge this grudgingly, because most of us spend a lot of time scraping clods of it from our spades, peeling it from our shoes and boots and vigorously complaining about it.

     Here is a short, crucial list of non-negotiable facts about soil:
Soil is NOT dirt. Soil is "the skin of the earth" that life on our planet depends on for sustanance. It is frighteningly shallow. There are many and varying estimates but it seems to be agreed that on average, world-wide good topsoil depth is less than a foot. This is a chilling statistic especially when one considers the VERY small percentage of the earth's surface that is suitable for agriculture.

     Soil is a living entity. A single gram(roughly a teaspoon) of soil can contain as many as 15,000 different life species...6 million creatures (mostly microscopic - but they still count.)

    
Soil has both TEXTURE and STRUCTURE...and all soils are different. TEXTURE describes the type and size of particles that make up a soil. Sand, the largest particle, silt the middle sized, and clay - the smallest, are combined in varying proportions to create different soils. (Think "sandy loam" or "silty clay". Clay mixed with sand will create cement which is not a good idea in a garden).
Texture has a lot to do with the movement of water and air through the soil - a process that happens continuously.

     STRUCTURE has a great deal to do with the manner in which soil particles group together. This is far more complex than it might seem. On the one hand, the micro and macro creatures that live in healthy soil contribute mightily to soil structure by releasing sticky compounds that "glue" small bits of soil together. This creates more surfaces for moisture, creates a moist "path" for bacteria to move on, creates areas for communities of microorganisms to grow and provides other benefits.
     On the other hand, healthy soil is a vigorously active chemical environment, generating not only the release and uptake of chemicals, some of them micro nutrients needed by plants, but also bound by electrical charges -ions and cations  - (pronounced cat-ions) that complicate the situation for the home gardener greatly.

We acknowledge the work of Rapid City Master Gardener Tom Allen in preparing information for Soils 101.

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