Union County Soil Data
Union County, Illinois
USDA SSURGO / PHZMAvg pH
6.3
Texture
Silt Loam
Drainage
N/A
Organic Matter
2.0%
Hydrologic Group
N/A
Data Story
About Soil in Union County, Illinois
Acidic Profile in the Southern Hills
Union County soil shows an average pH of 6.25, which is more acidic than the national median of 6.5 and the state average of 6.39. While specific taxonomic orders are not listed, this level of acidity is common in southern forest soils. Certain plants like blueberries or azaleas will find this environment particularly welcoming.
Fine Silt Dominates the Landscape
This soil is comprised of 67.6% silt, 23.2% clay, and just 9.2% sand. This fine-grained mix feels silky to the touch and holds onto moisture very effectively. However, the low sand percentage means the soil can become slick and heavy when wet, requiring careful timing for spring tilling.
Modest Organic Matter and Water Capacity
Organic matter sits at 1.95%, falling below the Illinois average of 2.94% and the national average of 2.0%. The available water capacity is 0.201 in/in, which is nearly equal to the state benchmark. Gardeners should consider adding compost to boost fertility and improve the soil's natural structure.
Managing Moisture in Silt-Heavy Ground
Official drainage class records are unavailable, but the high silt and clay levels suggest the ground may drain slowly. Because the soil holds 0.201 inches of water per inch of depth, it stays moist longer than sandier areas. Raised beds can help prevent root rot during the rainy southern Illinois spring.
Long Seasons in Zone 7a
Union County enjoys a mild Zone 7a climate, perfect for extended growing seasons and even southern favorites like okra. With the right organic amendments, this soil can support productive orchards and vibrant flower gardens. Start your seeds early to make the most of the long southern Illinois summer.
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 Union County have?
Union County's soil is classified as Silt Loam. This indicates the relative proportions of sand, silt, and clay — 9% sand, 68% silt, and 23% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Union County's soil acidic or alkaline?
Union County's soil has a pH of 6.3, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Union County?
Drainage class data is not currently available for Union County.
What crops or plants grow well in Union County's soil?
Based on Union County's Silt Loam texture, pH of 6.3, 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 Union County?
The dominant USDA soil order for Union County is not currently available in our dataset.
Soil & Planting Advisory: Union County
Soil Verdict
Union 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
Union County is somewhat warmer than the Illinois statewide average.
Planning your lawn? View lawn care data for Union 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.