Fairfax County Soil Data
Fairfax County, Virginia
Avg pH
5.1
Texture
Loam
Drainage
Well drained
Organic Matter
1.9%
Hydrologic Group
C
Data Story
About Soil in Fairfax County, Virginia
Acidic Entisols Define the Landscape
Fairfax County is dominated by Entisols, which are relatively young soils with little profile development. The average pH of 5.11 is more acidic than the state average of 5.23 and far below the national 6.5 median. This acidity typically requires lime amendments for traditional vegetable gardening.
The Balance of Loam Texture
The county's soil is classified as Loam, consisting of 43.3% silt, 38.2% sand, and 17.5% clay. This mix provides a classic balance that offers both easy digging and reliable nutrient holding. It represents a more versatile base for gardening than the sandier soils found in coastal Virginia.
Strong Water Retention Despite Low Organic Matter
Organic matter measures 1.94%, which is lower than the state average of 2.90% but nearly matches the national average. Available water capacity remains high at 0.161 in/in, outperforming the state average of 0.143 in/in. This means your plants have a better-than-average reservoir to draw from during hot spells.
Well-Drained Soils with Group C Hydrology
The soil is classified as well-drained, which is ideal for preventing root rot in most landscape plants. However, it belongs to hydrologic group C, suggesting a somewhat slow rate of water transmission when the ground is fully saturated. This combination requires careful management of storm runoff on sloped properties.
Thriving in Hardiness Zone 7b
In hardiness zone 7b, Fairfax gardeners can successfully grow everything from heat-tolerant azaleas to hardy winter greens. The loam texture is particularly well-suited for root vegetables like carrots if you manage the acidity. Get your hands in the dirt and take advantage of this well-drained loamy base.
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
Well drained
Water is removed from the soil readily but not rapidly. Optimal for most plants and construction.
Soil Profile
Dominant texture: Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Frequently Asked Questions
What type of soil does Fairfax County have?
Fairfax County's soil is classified as Loam. This indicates the relative proportions of sand, silt, and clay — 38% sand, 43% silt, and 18% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Fairfax County's soil acidic or alkaline?
Fairfax 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 Fairfax County?
Fairfax 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 Fairfax County's soil?
Based on Fairfax County's 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 Fairfax County?
Fairfax 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.
Planning your lawn? View lawn care data for Fairfax County on LawnByCounty.com →
Other Counties in Virginia
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.