The soil provides anchorage for the plant and stores the nutrients and water that support plant growth.
Soil is a layer of materials -- made up of minerals, organic matter, water and air -- capable of supporting plant growth. It also contains soil organisms. A typical garden soil would contain 45 percent mineral particles, 5 percent organic matter, 25 percent water and 25 percent air. Soils can vary widely between localities.
Soil management groups are based on soil texture. The texture is the relative percentages of sand, silt and clay particles that make up the soil. Various soils have different amounts of pore space, which affects soil aeration and drainage. Here are some groups and their compositions.
Texture: sand 0-45%, silt 0-40%, clay 40-100%
Dry: Clods cannot be broken with fingers without extreme pressure.
Moist: Quite plastic and usually sticky when wet; forms hard ball on drying; stains fingers; squeezes out at the right moisture into 1- to 3-inch, thin ribbons; shows fingerprints. A silty clay feels smooth; a sandy clay feels gritty.
Texture: sand 20-45%, silt 15-53%, clay 27-40%
Dry: Clods very difficult to break with fingers.
Moist: Has slightly gritty feel, forms moderately hard ball on drying; stains fingers, shows fingerprints; ribbons fairly well but ribbons will barely sustain their own weight; moderately sticky.
Texture: sand 23-52%, silt 28-50%, clay 7-27% Proportions are such that none predominates.
Dry: Clods moderately difficult to break; mellow, somewhat gritty.
Moist: Neither very gritty nor very smooth; forms firm ball; stains fingers; does not ribbon well, if at all.
Texture: sand 43-85%, silt 0-50%, clay 0-20%
Dry: Clods easily broken; sand can be seen and felt.
Moist: Moderately gritty; forms ball that can stand careful handling; definitely stains fingers.
Texture: sand 70-90%, silt 0-30%, clay 0-15%
Dry: Silt and clay may mask sand; feels loose, gritty.
Moist: Feels gritty; forms easily crumbled ball; stains fingers slightly; sand can be seen and felt.
Texture: sand 85-100%, silt 0-15%, clay 0-10%
Dry: Loose and single grained; feels gritty.
Moist: Will form very easily crumbled ball; does not stain fingers. Individual grains can be seen and felt.