St. Clair County Soil Data
St. Clair County, Illinois
Avg pH
6.5
Texture
Silt Loam
Drainage
N/A
Organic Matter
2.2%
Hydrologic Group
N/A
Data Story
About Soil in St. Clair County, Illinois
National Standard Soil pH
St. Clair County hits the national median pH of 6.50 exactly, making its soil chemistry an ideal benchmark. This is slightly higher than the state average of 6.39, offering a very balanced environment for nutrient absorption. This neutral foundation contributes to its respectable 75.9 soil score.
High Silt and Clay for Strong Structure
The soil profile consists of 66.8% silt and 24.2% clay, with a minimal 9.0% sand. This fine-textured mix is excellent for retaining essential minerals and supporting plant roots. However, the low sand content means the soil can be heavy and may require careful timing for spring tilling.
Superior Water Capacity for Hot Summers
Available water capacity stands at 0.208 in/in, surpassing the state average of 0.204. While the 2.16% organic matter is lower than the state's 2.94%, it remains higher than the 2.0% national average. This ensures that the soil stays productive even as temperatures rise in southern Illinois.
Water-Retentive Hydrologic Profile
Because sand makes up only 9.0% of the soil, drainage happens slowly and deliberately through silty channels. This characteristic is excellent for drought resistance but can lead to soggy conditions during wet springs. Managing surface runoff is a key consideration for both farmers and homeowners in this county.
Thriving in the Warmth of Zone 7a
St. Clair County's Zone 7a climate allows for a robust selection of long-season crops. The heavy, water-retaining soil is great for leafy greens, beans, and even heat-tolerant berries. With such a balanced pH, you can start planting a wide variety of species with confidence.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Hydrologic group data not available.
Drainage Class
Drainage class data not available.
Soil Profile
Dominant texture: Silt Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Frequently Asked Questions
What type of soil does St. Clair County have?
St. Clair County's soil is classified as Silt Loam. This indicates the relative proportions of sand, silt, and clay — 9% sand, 67% silt, and 24% clay. Loamy soils hold moisture well and support a wide range of plants.
Is St. Clair County's soil acidic or alkaline?
St. Clair County's soil has a pH of 6.5, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for St. Clair County?
Drainage class data is not currently available for St. Clair County.
What crops or plants grow well in St. Clair County's soil?
Based on St. Clair County's Silt Loam texture, pH of 6.5, and drainage class, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens.
What USDA soil order is found in St. Clair County?
The dominant USDA soil order for St. Clair County is not currently available in our dataset.
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Other Counties in Illinois
Soil data sourced from USDA SSURGO via Soil Data Access. Data is informational only and should not be used as a substitute for on-site soil testing. Contact your local NRCS office for site-specific soil information.