Soil permeability is the quality of a soil enabling it to transmit air or water through the soil pores. Texture, structure, cracking, and the amount of organic matter influence the permeability. The permeability of the least permeable horizon should be estimated because this becomes the most limiting horizon for water and air movement and root penetration. The soil permeability classes are slow, moderate, and rapid.
|< 0.6 inches of water move through the soil per hour. Slow permeability includes textures of silty clay, clay and sandy clay and soils with massive subsoils.
|0.6–6.0 inches of water move through the soil per hour. Moderate permeability includes textures of silt loam, loam, sandy clay loam, silty clay loam and sandy loam.
|6–20 inches of water move through the soil per hour. Rapid permeability includes textures of loamy sand and sand and soils with greater than 15 % gravel.