The beginning of Life in the Soil covers the abiotic (non-living) elements that create soil, generally at a rate of about an inch every 500 to 1,000  years.  The type of soil that will be formed in an area is influenced by the type of rocks involved, the topography of the site, climate, time, and living organisms.  Of these elements, the one I found most fascinating involved the chemical reactions that occur in rocks to create soil.

For example, I hadn't realized that clay and sand both have specific chemical formulas and are created when feldspar (an abundant mineral in many rocks) reacts with carbonic acid (formed from water and carbon dioxide).  All feldspars contain aluminum, oxygen, and silicon, and each also has one of the following constituents: potassium, calcium, sodium, and barium.  When carbonic acid (H₂CO₃) and potassium-based feldspar (2K(AlSi₃O₈)) react and spit out clay (Al₂Si₂O₅(OH)₄) and sand (4SiO₂), potassium carbonate is also formed.  Perhaps this is why old soils are often excessively high in potassium?

Another fascinating tidbit pertains to soil horizons.  If you've done any reading about soil, you probably know that natural soils have a layer of partially-decomposed plant matter (the O layer), beneath which is rich top soil (the A layer), then a small, pale E layer out of which the organic matter, clay, and nutrients have leached, followed by a slightly darker B layer.  Nardi explained that the textbook scenario is really only seen clearly in coniferous forests, where toxic levels of iron and aluminum build up in the B layer and keep most roots and soil life out.  In deciduous forests, in contrast, living things tend to mix the layers up, especially if earthworms have been introduced.

Stay tuned for more on the soil "mixers" in tomorrow's post.  In the meantime, you might want to check out my ebook for tips on taking a soil sample and learning more about your soil texture.