Soil Test Components
Soils vary widely in composition and structure from place to place. The best way to determine soil components is to use a soil test kit or hire a professional percolation test service. Soils are formed through the weathering of rock and the breakdown of organic matter. Weathering is the action of wind, rain, ice, sunlight and biological processes on rocks, which breaks them down into small particles. The proportions of minerals and organic matter determine the structure and other characteristics of a particular soil. Soils can be divided into two general layers (strata): topsoil, the topmost layer, where most plant roots, microorganisms, and other animal life are located, and subsoil, which is deeper and often more dense and contains less organic matter. Water and air are also components of soils. Mineral and organic solids comprise about half of the soil by volume. Water occupies the spaces between soil particles and is held by surface tension on particle surfaces. Air occupies the remaining void space. Both water and air components of soils are important to plant growth and other life in the soil profile of a particular ecosystem. The rock and mineral content of soils is categorized according to particle size, from sand (coarsest), to silt and clay (finest). The ratio of these particles to a great degree determines the soil classification and characteristics.