Sand, Silt, or Clay: What Have You Got in Your Soil?
Even those that live in big cities are surrounded by soil. Surprisingly enough their lives are constantly influenced by it, even when all the soil is buried under multiple layers of concrete and asphalt. Soil is not well tamed by man’s constant attempts to control and hid it. If you don’t believe me look at the history of sinkholes in Florida or landslides in any hilly or mountainous state. While there are other forces in play in those situations, it is also clear that what the soil does makes a big difference in how these phenomena interact with humans.
Of course my main interest in soils has to do with gardening, and so how I look at soils is heavily influenced by how soil interacts with plants. Let’s look at the main types of soil in your garden and see what their properties are.
SandSand is the largest of the soil particles. Each particle is just a small piece of gravel ranging in size from 2mm down to 0.05mm. Since sand is just small gravel it drains like gravel and does not do a good job of holding nutrients or water.
SiltSilt is a medium sized particle ranging from 0.05mm down to 0.002mm. Silt is too small to see, but is shaped just like sand. Because of the smaller size silt has a better time holding both water and nutrients. Silt is more worn down and has particles that are not as strong as sand, so it is more prone to loosing small amounts of mineral nutrients from each particle amounting to a lot more minerals being available to your plants.
ClayClay is the smallest of the soil particles and usually has a unique shape. Most clay has a flat shape that is more like a piece of paper or sheet metal. This special shaping gives it a huge amount of surface area for nutrients and water to stick to, making clay one of the best soils to grow plants in. Since clay is smaller than 0.002mm, water drains out very slowly. Clay particles are also linked in the soil in very convoluted patterns making it even more difficult to drain, but even so, many clay soils still have good drainage and don’t cause problems with the plants.
Most soils are a mixture of all of the above components, but may have one much more dominant than the other two. Often times I hear folks complain about sand and clay like they are out to destroy someone’s garden. I have worked with both and found that, even at the extremes, sand and clay can be very good growing soils and that most of the problems attributed to them is caused by something else in the soil, or is caused by a gardener not knowing how to properly use the soil they are complaining about. In fact, the one general rule most soil scientists have for improving sand or clay soil is to simply add organic material. So don’t complain about your soil, look for its most useful properties and make the best of it.