Soil Testing in Seattle, Washington

Nestled in the Pacific Northwest, Seattle, Washington, is renowned for its lush greenery, diverse landscapes, and maritime climate. The city's soils are shaped by a combination of factors, including abundant rainfall, temperate weather, and a mix of urban and natural environments. Understanding the intricacies of Seattle's soils is essential for sustainable development, landscaping practices, and environmental conservation in this thriving metropolis.

Glacial Till Soils: Much of Seattle's soil composition is influenced by the region's glacial history. Glacial till soils, formed by the deposition of sediment and rocks by ancient glaciers, are prevalent throughout the Puget Sound area. These soils are characterized by a mix of clay, silt, sand, and gravel, offering a diverse foundation for vegetation. The unique glacial till landscapes contribute to the city's natural beauty and support a wide variety of plant life.

Puyallup Silty Loam: In certain areas, particularly south of Seattle, Puyallup silty loam soils are common. These soils are a mixture of fine-textured silty materials and organic matter, making them fertile and suitable for agriculture. The Puyallup River Valley, known for its rich agricultural history, showcases the productivity of these soils, supporting crops ranging from berries to vegetables.

Urban Soils: Seattle's urban development has led to the creation of anthropogenic soils, shaped by human activities such as construction, landscaping, and pollution. The diversity in land use and the incorporation of green spaces within the city contribute to a range of urban soils with distinct compositions and characteristics. Understanding the impact of urbanization on soil quality is crucial for sustainable development and maintaining a healthy urban ecosystem.

Peat Soils: In some wetland areas around Seattle, peat soils can be found. These organic-rich soils develop over time from the accumulation of plant material in waterlogged conditions. Peat soils play a vital role in wetland ecosystems, serving as carbon sinks and supporting unique plant and microbial communities. Careful consideration of peat soils is essential to preserve the ecological balance of Seattle's wetlands.

Sandy Soils: Coastal areas like Alki Beach may feature sandy soils, composed of larger particles that provide excellent drainage. While sandy soils may have challenges in retaining water and nutrients, they are well-suited for certain coastal vegetation adapted to such conditions. Understanding the distribution of sandy soils is crucial for effective coastal landscaping and conservation efforts.

Volcanic Soils: The influence of volcanic activity is evident in the soils around Seattle, particularly in regions near the Cascade Range. Volcanic soils, rich in minerals and nutrients, provide fertile grounds for plant growth. Areas such as Mount Rainier and Mount St. Helens showcase the dynamic interplay between volcanic activity and soil development, contributing to the region's ecological diversity.

For soil sampling supplies, we recommend reaching out to these garden centers:

1. Swansons Nursery: 5-acre circa-1924 nursery for sustainable gardening, classes & seminars, plus a gift store & a cafe. It has a 4.7 star rating on Google Maps and address is 9701 15th Ave NW, Seattle, WA 98117, USA.

2. West Seattle Nursery & Garden Center: Nursery with big selection of trees, shrubs & plants, plus seeds, soil, tools & garden accessories. It has a 4.7 star rating on Google Maps and address is 5275 California Ave SW, Seattle, WA 98136, USA.

3. Magnolia Garden Center: Perennials, shrubs, trees & houseplants plus supplies for bird feeding & container gardening. It has a 4.7 star rating on Google Maps and address is 3213 W Smith St, Seattle, WA 98199, USA.

4. Ravenna Gardens: Stylish garden shop offering plants & accessories suitable for smaller indoor & outdoor spaces. It has a 4.6 star rating on Google Maps and address is 2600 NE University Village St, Seattle, WA 98105, USA.

5. Garden Center at The Home Depot: Garden center with a 4 star rating on Google Maps and address is 11616 Aurora Ave N, Seattle, WA 98133, USA.

Back to blog

Our tests

Have a question? Get in touch.

Understanding Soil Health

Assessing soil health involves looking at physical, chemical, and biological components.

Soil health is a fundamental concept that underpins the success of agriculture, gardening, and land management practices. It refers to the overall well-being and vitality of the soil ecosystem, encompassing physical, chemical, and biological aspects. Understanding soil health is crucial for maintaining sustainable and productive landscapes while also contributing to environmental conservation.

  1. Physical
    The physical properties of soil play a critical role in its health. These properties include soil texture, structure, compaction, and water-holding capacity. Soil texture refers to the proportions of sand, silt, and clay particles in the soil. A balanced texture allows for adequate water drainage and retention, preventing waterlogging and drought stress. Soil structure influences root penetration, aeration, and nutrient movement. Healthy soil structure promotes a friable and well-drained medium for plant growth.
  2. Chemical
    Soil chemistry directly affects nutrient availability and plant growth. Key chemical factors include soil pH, nutrient content, and the presence of contaminants. Soil pH measures the soil's acidity or alkalinity and profoundly influences nutrient uptake by plants. Nutrient content, including macronutrients like nitrogen, phosphorus, and potassium, must be in balance to support healthy plant growth. Monitoring and maintaining proper nutrient levels through fertilization are essential for maximizing crop yields and preventing nutrient deficiencies.
  3. Biological
    The biological component of soil health pertains to the diverse array of microorganisms, insects, and other organisms that inhabit the soil ecosystem. These organisms play crucial roles in nutrient cycling, organic matter decomposition, and disease suppression. Soil microorganisms break down organic matter, releasing nutrients that are subsequently made available to plants. A rich and diverse soil microbiome contributes to enhanced nutrient availability and plant resilience against diseases.

Our Soil Tests

We provide a range of soil tests from basic chemistry, to texture/infiltration rate, all the way to biology.

Order a Soil Test Kit

Basic Soil Health Test

The Basic Soil Health Test is an excellent starting point for understanding your soil's condition. It offers a comprehensive analysis encompassing pH levels, nutrient content, CEC (Cation Exchange Capacity), salts, and organic matter. This budget-friendly test is ideal for identifying potential soil health issues and establishing a solid foundation for further management.

Full Chemistry Test

Our Full Chemistry Test provides a detailed assessment of your soil's quality, guiding you towards healthy and sustainable soil management practices. Through an extensive analysis, we examine macro and micronutrient levels, pH, CEC, organic matter, and salinity. This comprehensive understanding empowers us to create tailored recommendations for soil amendments and treatments, optimized for the specific plants you intend to cultivate. By optimizing your soil's chemistry, you can expect to foster more robust and vibrant plant growth.

Complete Soil Health Test

Uncover a deeper understanding of your soil's health with the Complete Soil Health Test. This comprehensive analysis goes beyond the basics, measuring nutritional factors and examining soil texture. It covers macro and micronutrients, organic matter, pH, CEC, as well as sand, silt, and clay percentages. Additionally, we assess carbon sequestration levels, providing you with a holistic view of your soil's composition. The personalized recommendations derived from this test empower you to make precise adjustments to enhance your soil's health and productivity.

MWELO Soil Management Report

For those navigating California's MWELO guidelines, our MWELO Soil Management Report is an indispensable resource. This report not only ensures compliance but also promotes sustainable and thriving landscapes. It includes comprehensive data such as soil texture, infiltration rate, pH, total soluble salts, sodium content, and organic matter percentage. With amendment recommendations, optionally tailored to specific plant types, and annual maintenance tips, you'll be equipped to create landscapes that are both aesthetically pleasing and environmentally responsible.

Heavy Metals

The Heavy Metals analysis is a vital tool in assessing potential soil contamination. Given the uncertain history of properties, this analysis identifies the presence of heavy metals that might have accumulated due to past activities or nearby industrial sources. With results available in approximately nine business days, you'll gain insights to ensure the safety and health of your soil.

Soil Food Web

Explore the intricate world beneath the surface with our Soil Food Web analysis. By estimating population sizes of essential trophic groups‚ÄĒbacteria, fungi, protozoa, and nematodes‚ÄĒwe unveil the microbiological health of your soil. Additionally, we identify specific organisms within these groups, providing insights into the soil's successional level and overall condition. This analysis is applicable to soil, compost, and compost tea samples, offering a holistic perspective on your soil's biological vitality.

Pesticide Screening

The Pesticide Screening can detect hundreds on common pesticides that may have been applied or drifted from nearby sources.

Herbicide Screening

The Herbicide Screening plays an important role in ensuring the safety of your soil and plants. By detecting the presence of herbicide residues, this test can indicated whether a soil has had history of herbicide applications.

See our other tests.

Regenerative Soil Management Practices

Working with nature to improve soil means implementing practices like cover cropping, mulching, and composting.

Cover Cropping

Cover cropping involves planting specific crops during non-growing seasons to cover and protect the soil. These crops enhance soil structure, prevent erosion, suppress weeds, and provide organic matter when incorporated into the soil. Leguminous cover crops also contribute nitrogen fixation, enriching soil fertility naturally. Cover cropping is a sustainable method that improves soil health and biodiversity.


Mulching entails covering the soil surface with organic materials like straw, leaves, or wood chips. Mulch conserves soil moisture, moderates temperature fluctuations, suppresses weeds, and prevents soil erosion. As the mulch breaks down, it contributes organic matter, enriching the soil's structure and fertility. Mulching is an effective and easy way to maintain soil health.


Composting transforms organic waste into nutrient-rich compost. Incorporating compost into the soil enhances its structure, moisture retention, and fertility. Compost also introduces beneficial microorganisms that aid in nutrient cycling and disease suppression. Composting not only reduces waste but also revitalizes soil, making it an essential component of sustainable gardening.

Water Conservation Techniques

Implementing water-efficient practices such as drip irrigation, rainwater harvesting, and utilizing drought-resistant plants minimizes water use and reduces soil erosion. Conserving water in landscapes maintains soil moisture, supports plant growth, and sustains overall soil health. Water conservation techniques are vital for responsible gardening in arid and water-scarce regions.

If you have any questions feel free to get in touch with the Alluvial Soil Lab team at (831) 216-1367 or at

1 of 4