Minnesota soils have been mapped at scales and complexities ranging from page-sized state maps with general soil features to detailed site plots. Minnesota is part of the National Cooperative Soil Survey, which creates detailed soil maps at the county level. The county soil survey program was established in 1899 within the U.S. Department of Agriculture to help farmers determine the crops and management practices most suitable for the soils on their farm. As scientists learned more about soils, they investigated soil characteristics for other land uses. Modern soil surveys can be used for such diverse activities as highway construction, farm planning, tax assessment, forest management and ecological research.
Since the 1920s, aerial photography has been used as an aid for soil mapping and a presentation base for the final map. This has greatly increased the precision of soil surveys and permitted extensive mapping at detailed scales (1:24,000 or less). Participating in this effort have been federal and state agencies and the agricultural experiment stations of land grant universities, such as the University of Minnesota. The NCSS adheres to a set of standards for soil map production, data collection and publication of soil surveys, making it one of the most historically consistent resource surveys. Consistency in methodology and final products, used with a common system of soil classification and interpretation, allows nearly seamless soil interpretations across political boundaries for watershed, ecoregion, state or national levels.
One of the first county soil surveys in Minnesota was produced in 1906 for Blue Earth County. Early soil maps were crude because no standard mapping procedures existed. County surveys were created at a fairly slow pace for the next 50 years. By the end of 1963, only one-third of the state had been mapped. In 1977, Minnesota embarked on a 16-year program to accelerate the rate of soil survey mapping. This acceleration was justified by the state's pressing need for knowledge of the soil resource base to assess agricultural and forest productivity and to evaluate the environmental impacts of land use changes. The Legislative Commission on Minnesota Resources provided about one-third matching funding, in partnership with counties and the federal government, to complete or initiate mapping in all but three counties by the late 1990s.
A more detailed history of soil mapping in Minnesota can be found in a report published by the Minnesota Governor's Council on Geographic Information, County Soil Surveys: Guidelines for Digitizing, June 1997. For current information on the County Soil Survey program, see the Natural Resources Conservation Service website.
Soil scientists produce a county soil survey by observing the terrain, drainage patterns, native vegetative cover and the parent material from which the modern soils were formed. Soils are classified and named based on nationwide uniform procedures. Areas with similar soil characteristics, delineated on aerial photographs in modern county soil surveys, are called map units. Published soil surveys contain maps with various map units delineated on base maps, plus a variety of tables that show how various soils will respond to different land use applications.
The modern county soil survey is designed for basic land use and related natural resource planning and management. The survey contains descriptions of the physical and chemical properties of soils and interprets the capabilities and limitations of soils for agricultural, forestry and urban uses. Agricultural land uses have been a traditional focus of soil survey applications. Soil surveys also are being used for diverse applications, such as community planning of residential and commercial development, transportation, recreation, open space and natural areas, and in dealing with land use conversions. Modern county soil surveys, however, are not intended for site-specific land-use determinations, such as the siting or approval of individual septic systems. Finding suitable sites for such land uses usually requires on-site investigation of soil characteristics by a professional soil scientist.