Soil classification systems are established to help people predict soil behavior and to provide a common language for soil scientists. The National Cooperative Soil Survey and the USDA developed the Soil Taxonomy classification system, which is used worldwide. Soils are named and classified into 12 orders on the basis of physical and chemical properties in their horizon (layers). Soil taxonomy is used by farmers, builders, engineers, agricultural extension agents, homeowners, community planners and the government.
Knowledge of soil classification helps predict soil behavior. Soil behavior helps predict soil performance for growing agricultural crops. County extension agents provide soil survey maps of local soil classifications to help farmers make decisions about crops to grow in particular areas. Soil classified as vertisol has a high clay content, which shrinks and swells. The low organic-matter content of vertisol makes it poor agricultural soil, unless amended heavily.
Mollisol earth is the most productive soil for agricultural activity. Mollisol earth and its eight suborders make up 21.5 percent of the land in the United States. The productive agricultural area of the Great Plains is mollisol earth. Its topsoil layer is thick with organic matter and dark in color. The high fertility results from the long-term addition of organic materials derived from the grassy plant roots indigenous to the region.
Engineers and Community Planners
Engineers use soil classification surveys to determine the potential behavior and limitations of soil. Pipelines, bridges, buildings, recreation areas and landfills must be built on soil suitable to the engineering needs of each project. Community planners use soil classification knowledge to plan community gardens, green belts, recreation areas, septic absorption fields and the best use of local natural resources.
Maintaining Soil Fertility
Poor land-use practices such as deforestation, overgrazing and soil-damaging construction activity are examples of problems that are prevented with knowledge of soil types and classification. Erosion of formerly fertile soil layers affects 65 percent of the global land mass. Eroded soil is agriculturally unproductive. The soil classification system teaches the biological factors that affect soil formation, soil productivity and prevent erosion.