Soil survey maps and information are kept up-to-date using the USDA-NRCS SSURGO database.

Soil survey information is sourced from the NRCS's SSURGO database. The SSURGO database contains information about soil as collected by the National Cooperative Soil Survey. 

The information was gathered by walking over the land and observing the soil. Many soil samples were analyzed in laboratories. The maps outline areas called map units. The map units describe soils and other components that have unique properties, interpretations, and productivity.

The source and title of soil productivity values vary by state.

  • Iowa: The soil productivity value is CSR2 (corn suitability rating), which ranges in value from 5 to 100, as determined by Iowa State University.
  • Illinois: The soil productivity value is ¬†optimal PI (productivity index), which ranges from 0-150, as determined by Illinois Bulletin 811.
  • Minnesota: The soil productivity value is CPI (crop productivity index), which ranges in value from 0 to 100.
  • North Dakota: The soil productivity value is PI (productivity index), which ranges in value from 0 to 100.
  • South Dakota: The soil productivity value is PI (productivity index), which ranges in value from 0 to 100.
  • All other states: The soil productivity values are determined by the overall NCCPI (National Commodity Crop Productivity Index), which ranges in value from 0 to 100, as determined by the NRCS.

Land capability classes range from highest productive capacity to lowest (1-8).

  • Class 1 soils have few limitations that restrict their use.
  • Class 2 soils have moderate limitations that reduce the choice of plants or that require moderate conservation practices.
  • Class 3 soils have severe limitations that reduce the choice of plants or that require special conservation practices, or both.
  • Class 4 soils have very severe limitations that reduce the choice of plants or that require very careful management, or both.
  • Class 5 soils are subject to little or no erosion but have other limitations, impractical to remove, that restrict their use mainly to pasture, range land, forestland, or wildlife habitat.
  • Class 6 soils have severe limitations that make them generally unsuitable for cultivation and that restrict their use mainly to pasture, range land, forestland, or wildlife habitat.
  • Class 7 soils have very severe limitations that make them unsuitable for cultivation and that restrict their use mainly to grazing, forestland, or wildlife habitat.
  • Class 8 soils and miscellaneous areas have limitations that preclude commercial plant production and that restrict their use to recreational purposes, wildlife habitat, watershed, or aesthetic purposes.

The soil survey information on FarmlandFinder is updated annually across the U.S. using the the USDA-NRCS SSURGO database.

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