St. Clair County Soil Data
St. Clair County, Missouri
USDA SSURGO / PHZMAvg pH
5.9
Texture
Silt loam
Drainage
Very poorly drained
Organic Matter
2.7%
Hydrologic Group
C/D
Data Story
About Soil in St. Clair County, Missouri
Acidic Profiles in St. Clair
St. Clair County manages a soil score of 56.1, which reflects more challenging conditions than the state average. The average pH of 5.90 is notably acidic compared to the national median of 6.5, often requiring lime treatments for sensitive crops.
Higher Sand and Lower Clay
The soil mix contains 26.6% sand and 52.2% silt, which is sandier than many neighboring counties. With only 19.6% clay, this soil is generally easy to work but may lose nutrients more quickly than heavier soils.
Modest Organic Matter and Water
Organic matter sits at 2.72%, beating the national average but trailing the state's typical levels. The available water capacity of 0.178 in/in is slightly below the state average, meaning crops may feel the heat during Missouri summers.
Unclassified Drainage Dynamics
Standardized data for drainage class and hydrologic groups are currently unavailable for this county. Local observers should monitor how quickly water disappears after heavy rains to determine site-specific drainage needs.
Resilient Planting in Zone 6b
Native prairie grasses and acid-tolerant plants like blueberries can thrive in these conditions. With its 6b hardiness zone, the county offers a reliable window for summer vegetables if you manage the soil's acidity.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group C — Moderate-High Runoff
Soils with slow infiltration rates, often with a layer that impedes downward water movement. Higher clay content restricts drainage.
Drainage Class
Very poorly drained
Water is removed so slowly that free water remains at or on the surface most of the year. Typically wetland soils.
Soil Profile
Dominant texture: Silt loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Acidic Soil Detected
Your county's average pH is 5.9. These products help balance soil pH for healthier grass.
Browse Soil AmendmentsFrequently 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 — 27% sand, 52% silt, and 20% 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 5.9, 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?
St. Clair County has a dominant drainage class of "Very poorly drained." Poorly drained soils retain water for extended periods, which can limit crop choices and may require tile drainage or raised beds.
What crops or plants grow well in St. Clair County's soil?
Based on St. Clair County's Silt loam texture, pH of 5.9, and Very poorly drained, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens, rice, cranberries, and other water-tolerant species.
What USDA soil order is found in St. Clair County?
St. Clair County's dominant soil order is Entisols. Entisols are recently formed soils with little to no horizon development. They are common on floodplains, steep slopes, and sandy deposits.
Soil & Planting Advisory: St. Clair County
Soil Verdict
St. Clair County is in USDA hardiness zone 6b, a moderate climate zone. where winter lows can reach -5°F. Freeze-thaw cycles are moderate; soil biology slows in winter but recovers reliably in spring, supporting a broad range of plants.
Planting Guidance
A wide plant palette is possible: deciduous trees, most shrubs, cool-season vegetables, and many perennials thrive here. 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
Moderate freeze-thaw cycles naturally aerate the soil but can also cause compaction in clay-heavy areas; annual core aeration is beneficial. Organic matter amendments decompose at a moderate pace — aim for 3-5% organic content for optimal fertility. When soil temperatures drop below freezing, microbial nitrogen cycling stops; spring fertilization is more effective than late-fall application.
Regional Context
St. Clair County closely matches the Missouri average hardiness conditions.
Planning your lawn? View lawn care data for St. Clair County on LawnByCounty.com →
Other Counties in Missouri
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.