Soil Testing For California Landscapers and Landscape Architects (WELO)

Soil Testing For California Landscapers and Landscape Architects (WELO)

Our MWELO Soil Management Report provides a comprehensive physical and chemical analysis of the soil where your landscape will thrive. For new landscapes, the report offers pre- and post-plant recommendations with common fertilizer amendments, specified in pounds or cubic yards per 1000 square feet.

The reports we provide are designed to be user-friendly, making them accessible and understandable. Clients have the flexibility to choose between organic and conventional amendments. Our concise and easy-to-read amendment recommendations are available in electronic formats, simplifying the transfer of information to your design plans and specifications. This approach further contributes to the creation of a tailored plant selection, ensuring that the landscape is a perfect fit for the specific site and client requirements.

What is MWELO?

The Model Water Efficient Landscape Ordinance (MWELO) stands as a significant California state regulation, and its integration into the Building Code is aimed at preventing the wastage of water resources on irrigated landscapes. MWELO first started in 1993, emerging from the 1990 Water Conservation and Landscaping Act, and underwent revision in 2015 during the height of a severe drought period. 

Essentially, MWELO provides a framework for the strategic planning, design, installation, maintenance, and overall management of water-efficient landscapes in the context of both new constructions and the rehabilitation of existing landscaping. The overarching aim of MWELO is to ensure that landscapes are designed in a manner that not only promotes water efficiency but also caters to soil health, stormwater management, and erosion control.

To determine which projects fall under the purview of MWELO, it is important to note that the regulation applies to landscaping endeavors exceeding 500 square feet that necessitate permits, plan checks, or design reviews. Furthermore, it extends to encompass rehabilitation projects involving existing landscapes with an overall area surpassing 2,500 square feet.

For the purpose of submitting necessary documentation alongside Building/Planning application packets, four copies of the subsequent reports/plans are required:

  1. Landscape Design Plan
  2. Irrigation Design Plan
  3. Grading Design Plan (as applicable)
  4. MWELO Project Information Form (only one copy needed; details available on the last page)

Learn more about MWELO from the DWR here or contact them: 

Phone: (916) 715-7289


§ 18A.44 MWELO Requirements. (A) Individuals such as property owners, their designated building or landscape designers, and those in need of permits, plan checks, or landscape design reviews from the local jurisdiction, are obligated to adhere to Sections 492.6(a)(3)(B), (C), (D), and (G) of the MWELO, inclusive of stipulations concerning the utilization of compost and mulch, as articulated within this § 18A.44. This obligation pertains to the construction of new projects (single-family, multi-family, public, institutional, or commercial) characterized by a landscape area exceeding 500 square feet, as well as the rehabilitation of pre-existing landscapes encompassing a total landscape area exceeding 2,500 square feet.

(B) Additionally, the compost and mulch usage requirements that are integral components of MWELO have been incorporated into this article. It is pertinent to acknowledge that other MWELO requirements remain in effect and can be accessed in 23 CCR, Division 2, Chapter 2.7.

(C) Individuals encompassing property owners, their designated building or landscape designers, who meet the stipulated threshold for MWELO compliance outlined in § 18A.44(A) above, are expected to undertake the following actions:

  1. Adhere to Sections 492.6(a)(3)(B), (C), (D), and (G) of the MWELO, which entails the submission of a comprehensive landscape design plan complete with a segment focused on soil preparation, mulching, and amendments (see our soil test). This submission must encompass the following components: (a) Incorporation of compost at a minimum rate of four cubic yards per 1,000 square feet of permeable area for landscape installations, with incorporation extending to a depth of six inches into the soil. It's noteworthy that soils exhibiting organic matter exceeding 6% within the uppermost six inches of soil are exempted from this compost addition and tilling requirement. (b) Application of a three-inch minimum layer of mulch on all exposed soil surfaces within planting areas, excluding instances involving turf areas, creeping or rooting groundcovers, or direct seeding applications where the use of mulch is impractical. A deviation from mulching, covering up to 5% of the landscape area, is permissible to provide habitat for beneficial insects and other wildlife. Inclusion of designated insect habitat within the landscape design plan is imperative. (c) Preference for the use of organic mulch materials derived from recycled or post-consumer sources over inorganic materials or virgin forest products, unless locally available recycled post-consumer organic products are unattainable. It's important to acknowledge that local fuel modification plan guidelines or other pertinent local ordinances might prohibit the use of organic mulches in specific instances.

  2. The provisions of MWELO compliance delineated in this section should not be construed as an exhaustive list of MWELO requirements. Thus, individuals qualifying for MWELO compliance pursuant to § 18A.44(A) are strongly advised to refer to the comprehensive MWELO document to ensure comprehensive adherence to all stipulations.

(D) In the event that the California Department of Water Resources, or an entity succeeding it, modifies 23 CCR, Division 2, Chapter 2.7, Sections 492.6(a)(3)(B), (C), (D), and (G) of the MWELO's September 15, 2015 requirements subsequent to the adoption of this article, in a manner necessitating jurisdictions to integrate the updated MWELO requirements into local ordinances, and if these revised requirements establish provisions more stringent than those outlined within this section, then the augmented requirements within 23 CCR, Division 2, Chapter 2.7 shall be enforced.

Alluvial Soil Lab is located at 2100 Glen Canyon Rd, Santa Cruz, CA 95060.

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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—bacteria, fungi, protozoa, and nematodes—we 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

This page was written with the help of AI.

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