Knox County Soil Data
Knox County, Tennessee
USDA SSURGO / PHZMAvg pH
5.1
Texture
Silt loam
Drainage
Well drained
Organic Matter
1.4%
Hydrologic Group
D
Data Story
About Soil in Knox County, Tennessee
Weathered Ultisols of the Valley
Knox County’s soil is classified as Ultisols, which are older, highly weathered soils. The average pH is 5.12, which is more acidic than the Tennessee state average of 5.35 and much lower than the national median of 6.5.
Knox County’s silt loam mix
The soil is a silt loam texture featuring 43.0% silt, 29.2% sand, and 20.9% clay. This combination provides a relatively stable surface for development while remaining workable for agricultural use.
Lower nutrient and water levels
Organic matter is relatively low at 1.42%, trailing the state average of 2.44%. The available water capacity of 0.152 in/in is also below the state average of 0.171, suggesting a need for supplemental irrigation during dry spells.
Well-drained but low infiltration
The soil is well-drained but belongs to hydrologic group D, which indicates very low infiltration rates when thoroughly wet. This can lead to high runoff during heavy storms, a critical factor for urban planning in Knoxville.
Urban gardening in Zone 7b
Zone 7b supports everything from kale to tomatoes. To compensate for the low organic matter, incorporate plenty of compost and use raised beds to manage the soil's drainage characteristics.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group D — High Runoff
Clay soils with very slow infiltration rates. Highest runoff potential. These soils have a permanent high water table or are shallow over impervious material.
Drainage Class
Well drained
Water is removed from the soil readily but not rapidly. Optimal for most plants and construction.
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 5.1. These products help balance soil pH for healthier grass.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Knox County have?
Knox County's soil is classified as Silt loam. This indicates the relative proportions of sand, silt, and clay — 29% sand, 43% silt, and 21% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Knox County's soil acidic or alkaline?
Knox County's soil has a low pH of 5.1, which is strongly acidic. Acidic soils benefit from lime applications to raise pH and improve nutrient availability.
What is the drainage class for Knox County?
Knox County has a dominant drainage class of "Well drained." Well-drained soils allow excess water to move through quickly, reducing waterlogging risk and supporting most field and garden crops.
What crops or plants grow well in Knox County's soil?
Based on Knox County's Silt loam texture, pH of 5.1, and Well drained, the soil is well suited for acid-loving plants like blueberries and azaleas, row crops and vegetable gardens, most annual and perennial crops.
What USDA soil order is found in Knox County?
Knox County's dominant soil order is Ultisols. Ultisols are highly weathered, clay-rich soils common in humid regions. They are low in natural fertility and often require lime and fertilizer for agriculture.
Soil & Planting Advisory: Knox County
Soil Verdict
Knox County is in USDA hardiness zone 7b, a moderate climate zone. where winter lows can reach 5°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. 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.
Regional Context
Knox County closely matches the Tennessee average hardiness conditions.
Planning your lawn? View lawn care data for Knox County on LawnByCounty.com →
Other Counties in Tennessee
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.