OFRF Farmer Led Trials: Occultation Tarping as a No-till Strategy for Weed Suppression and Soil Health Management

Rhianna Simes, Verdant Phoenix Farm

Farm Trial Overview

Rhianna Simes, M.S.Ed. owns and operates Verdant Phoenix Farm, a 10-acre urban farm and education center located in Jackson County, Oregon. The farm is managed as a no-till production system and is certified organic. Rhianna operates the farm as a research and education hub, hosting educational workshops, hands-on demonstrations and farm tours. She sells nursery stock, seeds, basketry willow, plant starts, and other products through the farm stand and on their website.

Rhianna has been using occultation tarping to terminate cover crops and manage weeds while protecting soil health for years. With technical support from OFRF, Rhianna decided to create a farm trial that would compare the use of occultation tarping in no-till and tilled conditions.  Soil sampling was the primary way to measure differences in these practices and she  evaluated soil parameters such as soil organic matter, carbon mineralization potential, and aggregate stability.

For full details on the study’s methodology and results, check out the OFRF Farmer Led Trials Blog, or read the final report linked here.

Download Final Report

Funding Amount

$1,500

Funding Year

2024

Location

Jackson County, Oregon

Collaborators

Verdant Phoenix Farm

Organic Farming Research Foundation

Key Findings

  • Effective Weed Suppression: Tarped plots had significantly fewer weeds, demonstrating that occultation tarping is a viable alternative to tillage for weed control.
  • Increased Soil Moisture Retention: Soil moisture levels were higher in tarped plots compared to non-tarped areas, highlighting the potential of this method to improve drought resilience.
  • Short-Term Reduction in Soil Respiration: While tarping suppressed weeds effectively, it also temporarily reduced soil respiration and nitrogen levels, suggesting lower microbial activity in the short term.
  • Long-Term Soil Health Benefits: Despite initial reductions in biological activity, visual observations showed improved soil structure and aggregation in tarped plots, indicating potential long-term benefits for soil health.

Based on these findings, Rhianna plans to continue using occultation tarping as a tool for weed management and soil conservation. Future research could explore how repeated tarping affects soil biology over multiple seasons and its impact on crop yields.

Region

Western

Topic

Soil Health, Weed Management, Cropping Systems

Category

Vegetables/Fruits

Year Published

2025