Multnomah County Soil Data
Multnomah County, Oregon
Avg pH
5.4
Texture
Silt Loam
Drainage
N/A
Organic Matter
21.6%
Hydrologic Group
N/A
Data Story
About Soil in Multnomah County, Oregon
The Acidic Profile of the Metro Area
Multnomah County features an average pH of 5.35, which is notably more acidic than the national median of 6.5. This acidity is typical for the Pacific Northwest and slightly higher than the Oregon state average of 5.26. It creates a perfect environment for acid-loving plants like blueberries and rhododendrons.
A Silt-Heavy Foundation
The soil contains 50.8% silt and 29.6% sand, creating a silty texture that is easy to cultivate. With only 16.7% clay, the soil offers a good balance of moisture retention and workability. This mix prevents the heavy compaction often found in higher-clay regions.
Rich Organic Content for Urban Growth
The county boasts an impressive 21.64% organic matter, dwarfing the national average of 2.0%. While this is below the state average of 29.41%, it provides a nutrient-dense base for gardening. The available water capacity of 0.244 in/in ensures that plants remain hydrated between rains.
Navigating Multnomah's Hydrology
While specific drainage classes aren't recorded in this data, the high silt content suggests moderate permeability. Builders and farmers should monitor runoff carefully, especially in the hilly areas of Portland. The soil's structure generally supports diverse urban agriculture and landscaping projects.
Gardening Success in Zone 9a
Falling into hardiness zone 9a, Multnomah County has a mild climate that extends the growing season. You can easily grow lush greens, fruit trees, and native shrubs in this rich soil. Get your garden started with confidence in one of Oregon's most fertile urban pockets.
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
Frequently Asked Questions
What type of soil does Multnomah County have?
Multnomah County's soil is classified as Silt Loam. This indicates the relative proportions of sand, silt, and clay — 30% sand, 51% silt, and 17% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Multnomah County's soil acidic or alkaline?
Multnomah 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 Multnomah County?
Drainage class data is not currently available for Multnomah County.
What crops or plants grow well in Multnomah County's soil?
Based on Multnomah County's Silt Loam texture, pH of 5.4, and drainage class, the soil is well suited for acid-loving plants like blueberries and azaleas, row crops and vegetable gardens.
What USDA soil order is found in Multnomah County?
The dominant USDA soil order for Multnomah County is not currently available in our dataset.
Planning your lawn? View lawn care data for Multnomah County on LawnByCounty.com →
Other Counties in Oregon
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.