General state soil maps in the USA

Abstract

The historical development of state general soil maps is examined over the time intervals of pre-1927, 1927–1960, 1960–1999, and post-1999, which correspond to major periods in the development of soil classification schemes in the USA. Eleven states developed general soil maps prior to the development of the country's first soil classification scheme in 1927, and these were created for agriculture and based primarily on soil-physiographic provinces. Twenty states prepared general soil maps during the period in which zonal soil classification schemes were employed (1927–1960). Although physiography continued to be a primary basis of soil mapping, soil associations were used in 56% of the maps. The time period between the publication of the Seventh Approximation (1960) and the second edition of Soil Taxonomy (1999) was the “golden era” for general soil maps, with 46 states (92%) making them available to the public in hardcopy format, primarily as soil series-association maps. There was a dramatic reduction in the generation of state soil maps from 1999 to 2014 (to 22 states), largely because of the digital age. Individuals with GIS expertise were encouraged to develop their own maps using STATSGO and SSURGO databases. Initiated in 2005 the Web Soil Survey has enabled the public to produce maps for areas of less than 40,500ha. The level of detail in state soil maps has increased over time, but soil-series association maps remain a popular venue. General maps using Soil Taxonomy provide valuable information regarding the nature, properties, and soil-forming factors and processes of soils, as well as their geographic distribution. General state maps remain important as a natural resource data layer and for instructional purposes.