People often take soil for granted, but without healthy soil, growing healthy plants is extremely difficult. Most soil is made up of a combination of clay, sand and silt, which are differentiated primarily by the size of the particles. Some soils drain well, promote good air circulation and retain nutrients, while others are difficult for roots to penetrate, don't drain well and are nutrient-poor. The best soil type for growing plants is loam, which is made up of a combination of clay, sand and silt.
Clay particles are smaller than sand or silt. Although clay is smooth when it's dry, it feels slick and sticky when it's wet, and will hold its shape if you attempt to roll a small amount of wet clay into a ball. Clay soil is often referred to as "heavy" soil, because when it's wet, it becomes heavy and sticky like putty, and when it dries, it can be hard and difficult to penetrate. Although clay is nutrient-rich, it doesn't drain well and does not allow for good air circulation. Most plants don't do well in clay soil.
Sandy soil feels gritty, and the grit can be either coarse or fine. Sand won't compress when you attempt to shape it into a ball. Although sand has the largest particles of all the soil types, it holds very few nutrients, and water drains through it very quickly. Although certain plants, such as cactus, do well in sandy soil, most plants require soil that retains nutrients and moisture for a longer period of time.
Silt particles are larger than clay, but smaller than sand. After a rain, silt will form a crusty surface that prevents good drainage and air circulation, and is difficult for plants to penetrate. Silt feels smooth when you rub it between your fingers. When you attempt to shape it into a ball, silt will hold together only as long as you apply pressure.