Soil - First Things You Need To Know

Soil is perhaps the most overlooked part of the garden. It’s always underfoot, but seldom on the mind. Gardeners - especially those who are new to it - spend a lot of time thinking about colors, bloom season, days to maturity and landscape design, but not so much about what supports it all. Fact is, other considerations come to naught if the foundation, soil, isn’t carefully reviewed. Unless you’ll be gardening in containers or hydroponically (artificially in soil-less, nutrient-rich solutions), you’ll understand that you can’t start with a blank slate, so to speak. What you have underfoot is, basically, what you’ll have to work with. Want to skip ahead and dream about your future garden? Already an active gardener? Visit GoGardenNow.com. Want to know more about soil? Read on! What is soil, exactly? The USDA defines it like this: Soil is a natural body comprised of solids (minerals and organic matter), liquid, and gases that occurs on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment. Let’s break it down. Soil includes: Solids Minerals – Inorganic solids with definite chemical compositions in crystal forms formed by geologic processes. Examples include magnesium, sodium, iron, copper, and zinc. Organic matter – These are left-overs of dead plants and animals. Examples include shells, bones, hair, feathers, leaves, grass, wood, and such cell structures in various stages of decomposition. “But”, you might ask, “what about rocks?” Rocks are aggregates of different minerals – and sometimes even organic solids – bound together as a solid mass. Liquids – Water, mostly. It’s estimated, though, that only 0.01% of all the water on earth is stored between soil solids. Gases – Oxygen, nitrogen, carbon dioxide, methane, radon. These fill the rest of the spaces between soil solids and liquids. Layers or Horizons – These are easily identified one from another. Horizons are laid one upon another by age and subject, and moved around by water, wind, tectonic forces, and big machines. You might have bedrock at the very bottom, several layers of silt interspersed with layers of ash from fires or volcanoes, and a layer of soft, dead plant and animal matter at the very top. The layers – horizons – have actually been named so we can wrap our heads around them. They are Horizon O, Horizon A, Horizon B and Horizon C. Horizon O is the topmost soil that we tread. It’s pretty shallow, made up of dead and decaying organic material. It’s quite fertile. Horizon A is just beneath Horizon O. It’s made of organic material in advanced stages of decomposition, helped along by fungi, nematodes and earthworms, eating and being eaten, adding further to the richness. Horizon B, the one beneath A, is very thick and dense. So dense, in fact, that it is impenetrable by all but the most violent forces. Finally, there’s Horizon C, the basis of all that lies above it. This layer consists of bedrock and other materials that long ago were compressed into stone. Obviously, soil will present different colors – red, yellow, white, brown, gray, black – and textures – hard, soft, crumbly, gritty, sticky, slippery – depending upon the constituent parts. Soil takes a long time to make Soil-making is a natural process, and natural processes can take a very long time. Creation of topsoil – Horizon O – probably takes the least amount of time. It doesn’t take long for leaves of grass, little critters and such to die and decompose to the point that they’re unidentifiable and look like plain old dirt. Much larger corpses, like humongous trees, will take longer. The deeper we dig, the longer it took for those layers to become. We find, not just relics of the recent past, but ancient history right below our feet. Because it takes so long to create, soil is a valuable resource. Let's take good care of it. For Now and In The Future In a future article, we’ll discover more about the soil that is the foundation of your gardening plans. Meantime, check out our other articles in GoGardenNow  – The Gardening Blog. You’ll find lots of insights and tips on plants, gardening, garden tours, and answers to frequently asked gardening questions. Our Gardening Resources page presents a wealth of links to just about every plant society and team of horticulture experts imaginable.