Slide 7 of 8
Although soils consist primarily of sand, silt, and clay, there are over 70,000 different types of soils around the globe. There are many characteristics that differentiate one soil from another; for example, amounts of nutrients available, erosion potential, and permeability. Physical characteristics are the easiest to observe and by examining only a few, several generalizations can be made about soil. Two important physical characteristics (or traits) are color and texture.
Color - There are three color categories of topsoil which relate to the amount of organic matter:
1. Dark soils -- black, dark gray, or dark brown. Rich in organic content and
usually very fertile. They are excellent for gardening and agriculture.
2. Moderately dark soils - range from brown to yellow-brown. They moderate
amounts of organic matter and are of medium fertility. They can be good for
3. Light colored soils -- pale brown to yellow. They are low in organic matter,
fertility, and are sometimes poorly aerated.
Texture - Soils can be classified into three groups by texture: clayey, sandy, and loamy. To test, wet a small amount of soil and rub it between your fingers. Clayey soils are smooth and sticky; sandy soils are very gritty; and loamy soils are between these two extremes.