Clark County Soil Data
Clark County, Washington
Avg pH
5.4
Texture
Cobbly silt loam
Drainage
Well drained
Organic Matter
4.9%
Hydrologic Group
B
Data Story
About Soil in Clark County, Washington
Acidic Inceptisols of the Trough
Clark County is dominated by Inceptisols with a quite acidic pH of 5.43, well below the national median of 6.5. This cobbly silt loam profile is typical of the weathered landscapes in the southern Puget Trough.
Silt-Rich and Highly Workable
The soil is a mix of 30.2% sand, 46.1% silt, and 18.1% clay. This high silt content provides good workability and decent nutrient retention, though the clay adds some necessary structure for plant roots.
Healthy Matter and Water Storage
Organic matter is strong at 4.88%, more than double the national average of 2.0%. Available water capacity sits at 0.178 in/in, providing a solid foundation for plant health even during the dryer summer months.
Reliable Drainage for Development
These soils drain well and belong to hydrologic group B, making them excellent for residential development. Water moves through the profile efficiently, which prevents significant ponding during the heavy rainy season.
Blueberries and Rhodies in Zone 8b
Within hardiness zone 8b, your garden can flourish with everything from kale to figs. The acidic soil is particularly welcoming to blueberries and rhododendrons, so start planting your Pacific Northwest favorites today.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group B — Moderate Runoff
Moderately deep, moderately well-drained soils with moderate infiltration rates. Good balance of drainage and water retention.
Drainage Class
Well drained
Water is removed from the soil readily but not rapidly. Optimal for most plants and construction.
Soil Profile
Dominant texture: Cobbly silt loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Frequently Asked Questions
What type of soil does Clark County have?
Clark County's soil is classified as Cobbly silt loam. This indicates the relative proportions of sand, silt, and clay — 30% sand, 46% silt, and 18% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Clark County's soil acidic or alkaline?
Clark County's soil has a low pH of 5.4, which is strongly acidic. Acidic soils benefit from lime applications to raise pH and improve nutrient availability.
What is the drainage class for Clark County?
Clark 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 Clark County's soil?
Based on Clark County's Cobbly silt loam texture, pH of 5.4, 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 Clark County?
Clark County's dominant soil order is Inceptisols. Inceptisols are young soils with weak horizon development. They occur in a wide range of climates and parent materials.
Planning your lawn? View lawn care data for Clark County on LawnByCounty.com →
Other Counties in Washington
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.