Illinois Technical Resources

Illinois Suite of Maps

These maps were produced from data available from the USDA-Natural Resources Conservation Service Soil Data Mart. Please send your comments to Bob McLeese, State Soil Scientist.

Soil Order

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Brief description of classes

Mollisols are soils formed under prairie vegetation, characterized by dark, surface horizons
Alfisols are soils formed under forest vegetation
Entisols are young soils, typically alluvial or disturbed, that show limited signs of soil development
Inceptisols show more signs of soil development than Entisols
Histosols are organic soils

Full descriptions are available in Soil Taxonomy

Prime Farmland

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Prime farmland is land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber and oilseed crops.

Farmland of statewide importance, is land other than prime farmland or unique farmland but that is also highly productive.

Detailed descriptions are available in the Soil Survey Manual

Hydric Soils

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Hydric soils are soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part. They make up part of the criteria for the identification of wetlands.

Detailed descriptions are available in the Soil Survey Manual

Floodplains

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Soils that are classified as 'fluvic' at the suborder or subgroup level in Soil Taxonomy, or have a flooding phase in the soil map unit name.

Drainage class

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Detailed descriptions are available in the Soil Survey Manual

Potential Tile Drainage extent

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This map is an interpretation of the soil groups in the Illinois Drainage Guide. It was assumed that very poorly and poorly drained soils that are rapidly permeable to moderately slowly permeable would be very likely to be tile drained. Soils that are somewhat poorly drained, that are rapidly permeable to moderately slowly permeable are likely to be tile drained. Soils that are slowly or very slowly permeable are unlikely to be tile drained. This has not been verified and is to only be used as a general guide.

Potential Native Vegetation

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Taxonomic classification, based on Soil Taxonomy was used to predict native vegetation. Native in this case would be considered the period of time after transition from a tundra biome ~12,000BP, after the last glacial advance, to forest and grassland biomes. General interpretation rules:

Alfisol order - Woodland
Mollic subgroups of the Alfisol order - Savanna
Mollisol order - Prairie
Entisol order - Woodland
Inceptisol order - Woodland
Histosol order - Marshland

Alluvial soils were interpreted as being Woodland independent of soil classification. This is a generalization, but given the dynamic nature of alluvial systems, there wasn't an adequate way to differentiate the variable vegetation types that may have been present on these types of soils prior to widespread settlement.

Productivity Index

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Map is based on the Soil Productivity Index for optimal levels of management as described in Bulletin 811, developed by the University of Illinois. Areas that are white were not rated and include water bodies, disturbed soils or soils that commonly have flooding of long duration. Local officials are responsible for the assignment of a Productivity Index for each soil map unit within a county. This map was developed by NRCS for descriptive purposes only.

For More Soils Information Contact:

Bob McLeese State Soil Scientist
(217) 353-6643