Occultation Impacts on Soil Health and Plant Termination in Oregon

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2024: $22,785.00
Projected End Date: 04/01/2027
Host Institution Award ID: G253-24-WA507
Grant Recipient: Verdant Phoenix Farm
Region: Western
State: Oregon
Principal Investigator:
Rhianna Simes
Verdant Phoenix Farm


  • Agronomic: corn, radish (oilseed, daikon, forage)
  • Vegetables: beans


  • Crop Production: no-till
  • Education and Training: on-farm/ranch research
  • Soil Management: soil analysis

    Proposal summary:

    Occultation tarping has the
    potential to transform Oregon’s small farm management practices
    in ways that help farmers save money, access in-expensive, easy
    to implement strategies to terminate cover crops, and manage
    weeds in the field while protecting soil tilth. We want to study
    this ‘ground-breaking’ no-till strategy to better understand the
    impacts on soil health and plant termination. 

    Occultation, “weeding with tarps”
    involves laying down a thick, black plastic /vinyl tarp for 4-8
    weeks. Under the tarp, the weed seeds germinate in the moist
    environment, plants die due to lack of sunlight, and then
    decompose back into the soil with the help of the active soil
    food web.
    Once the tarp is
    removed, the clean seed bed is planted/seeded and minimal soil
    disruption occurs.

    Our research question is, “What
    effects does occultation have on plant termination and soil
    health?” We will contract with OSU Soil Lab to conduct soil tests
    encouraged by the Soil Health Institute to measure the effect of
    occultation on
    organic carbon concentration, carbon mineralization potential,
    and soil aggregate stability. These are all indicators of soil

    Verdant Phoenix Farm’s team
    includes a professional educator / experienced no-till farmer, a
    retired PhD research advisor, farm assistant, and technical
    advisor / ag professional from Jackson Soil and Water
    Conservation District. Our project has significant support
    because there are a growing number of organic farmers interested
    in no-till, but they are not sure how to terminate plants and
    protect soil tilth.

    We plan to share our findings
    through field days, on-farm demonstrations, and through
    interviews on the popular No-Till Growers podcast (reaching over
    15,000 listeners weekly), and has over
    275,000 YouTube subscribers,
    ur team will also develop
    a “
    Guide for
    occultation implementation: Occultation Protocol for No-Till
    Systems in Oregon
    share the practice in Oregon and beyond.


    Project objectives from proposal:

    Project Research Objectives: Our project will determine if occultation
    tarping has a positive impact on:

    1. Soil organic carbon
      concentration, compared to tillage.
    2. Soil carbon mineralization potential
      compared to tillage.
    3. Soil aggregate stability
      compared to tillage.
    4. Plant termination by
      percentage. Qualitatively measure, through observation and
      photo documentation the percentage of plants terminated using a
      1 = < 10%, 2= >20%, 3= <50%, 4=> 50%,
      5= >90%

    Education Objectives:

    Objective 1: Develop case
    study, record observations, photo document, and record impact
    data on soil health, plant termination, and crop yield over the
    course of the project.

    Objective 2: Establish
    educational field tours to demonstrate occultation techniques,
    impacts, and benefits to producers, gardeners, land managers, and
    ag professionals.

    Objective 3: Plan, design,
    and write a fact sheet and publication to serve as a
    Guide for occultation
    implementation: Occultation Protocol for No-Till Systems in
    ”. We will work
    with the project team, our technical advisor, research advisor,
    ag professionals from SOU, JSWCD, and OSU Small Farms to
    collaboratively develop content and publish the

    Guide for use by other farmers and producers.
    (Letters of support included) This Guide will be available in
    print (at least 200) and our team will pursue publishing the fact
    sheet through OSU Extension.

    Objective 4: Present
    findings through in-field demonstrations and presentations for
    OSU Small Farms program, OSU Small Farms Conference, Jackson Soil
    and Water Conservation District (JSWCD) workshops, OSU Land
    Steward classes, Friends of Family Farmers, and others when
    requested. At least 100 people will attend. 

    Objective 5: Print and
    distribute fact sheet / "Guide" through ag partners, technical
    advisor, and other community partners so that over 200 copies are
    provided to interested producers and ag professionals to increase
    the impacts of this research and broader adoption of the

    Objective 6: Prepare and
    deliver an online workshop / podcast to disseminate project
    findings via “No-Till Growers” podcast online. No-Till Growers
    have an active listening audience
    of approximately 15,000 weekly podcast listeners and 275,000 YouTube subscribers,
     No-Till Growers have committed to
    supporting this project (letter included) and their goal is to
    help promote and share no-till strategies so there is greater
    adoption of the practice.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.