Williamson County Soil Data
Williamson County, Illinois
USDA SSURGO / PHZMAvg pH
6.0
Texture
Silt Loam
Drainage
N/A
Organic Matter
1.6%
Hydrologic Group
N/A
Data Story
About Soil in Williamson County, Illinois
Acidic Profiles in Southern Illinois
Williamson County has an acidic soil profile with a pH of 6.03, falling below the state average of 6.39. This is significantly lower than the national median of 6.5. Gardeners here may need to monitor pH levels closely to support sensitive plants.
Heavy Silt and Clay Mix
The soil is exceptionally silt-heavy at 69.3%, with a very low sand content of only 9.1%. Combined with 21.7% clay, this creates a 'heavy' soil that can feel sticky when wet and hard when dry. This composition requires careful timing for tilling to avoid damaging the soil structure.
Challenges in Organic Matter
Fertility is lower here, with organic matter at 1.61% compared to the 2.94% Illinois average. The available water capacity of 0.202 in/in is nearly identical to the state benchmark, providing decent moisture for roots. These factors lead to a total soil score of 57.5.
Navigating Moisture and Runoff
Specific hydrologic groups and drainage classes for the dominant soils are not currently available in the records. The high silt and clay levels often indicate that drainage may be restricted during heavy rains. Proper land grading is essential for successful building and farming projects.
Long Seasons in Zone 7a
Situated in the warmer Hardiness Zone 7a, this county supports a long growing season for heat-loving plants. Focus on acid-tolerant crops like blueberries or peppers which thrive in these conditions. With a little soil building, your southern Illinois garden can be highly productive.
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
Soil Amendment Products
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Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Williamson County have?
Williamson County's soil is classified as Silt Loam. This indicates the relative proportions of sand, silt, and clay — 9% sand, 69% silt, and 22% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Williamson County's soil acidic or alkaline?
Williamson County's soil has a pH of 6.0, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Williamson County?
Drainage class data is not currently available for Williamson County.
What crops or plants grow well in Williamson County's soil?
Based on Williamson County's Silt Loam texture, pH of 6.0, 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 Williamson County?
The dominant USDA soil order for Williamson County is not currently available in our dataset.
Soil & Planting Advisory: Williamson County
Soil Verdict
Williamson County is in USDA hardiness zone 7a, a moderate climate zone. where winter lows can reach 0°F. Mild winters mean soil rarely freezes deeply, allowing year-round microbial activity and faster organic matter breakdown.
Planting Guidance
Warm-season crops, citrus relatives, and heat-loving ornamentals do well. Cool-season vegetables should be planted in fall and winter. Winter protection (mulch, burlap wraps) helps push the zone boundary for desired species. Always match plant selections to the specific microclimate of your property — low spots, slopes, and wind exposure can shift effective hardiness by half a zone.
Soil Implications
Warm soils accelerate organic matter breakdown, so compost and mulch need replenishing more frequently than in cooler zones. Sandy soils common in warm zones drain quickly; water-retentive amendments like compost or peat help hold moisture. When soil temperatures drop below freezing, microbial nitrogen cycling stops; spring fertilization is more effective than late-fall application.
Regional Context
Williamson County is somewhat warmer than the Illinois statewide average.
Planning your lawn? View lawn care data for Williamson County on LawnByCounty.com →
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.