Moving Towards Sustainable Mulching Practices: Comparing Outcomes from Traditional and Bio-based Mulches via Experimentation and Education

Commodities

Practices

Plastic pollution has quickly become one of the most pressing modern environmental challenges. Both macro and microplastic pollution are problematic throughout food systems, but given current economic realities, agricultural plastic use is often necessary to generate sufficient crop yields. For example, plastic mulch films are essential for reliable and cost-efficient crop production, even in organic farming. However, traditional plastic mulch films unintentionally contribute to global plastic pollution, and may also have adverse effects on soil, crop health, and surrounding ecosystem health as they breakdown into microplastics from UV light exposure. Bioplastic- based, wool, and paper sheet mulches are available alternatives; however little is known about how they compare to traditional mulches for food crops, and they can also be more costly, which is an understandable concern. There are also few studies comparing the same mulch treatments between organic farms and a greenhouse setting, allowing for an evaluation of impacts in both a real-world and controlled scenarios. Our proposed study aims to compare the breakdown and effects (e.g. microplastic breakdown, soil health, crop yield, and organism uptake/health) of traditional, bioplastic, wool, and paper sheet mulches in food crop systems on four organic farms in the Willamette Valley – Rainshine Farm, Riverland Farm, Upriver Organics, and Gathering Together Farm. Managers from fully compensated farms will have the opportunity to inform study design from project onset to completion, which will provide a framework for grower initiated movement towards the use of potentially more sustainable materials for crop mulching. Furthermore, we expect that working with growers on mulching alternatives will create a springboard for additional collaborations and creativity going forward on the many other aspects of farming that rely on plastics. By collaborating closely with producers throughout, we plan to collect data on parameters such as microplastic fragmentation, chemicals leaching from mulches, effects on moisture retention, mineral content, benthic organism health, and crop yield that can be used in a comprehensive cost-benefit analysis to understand the logistical and financial feasibility of potentially transitioning to alternative mulch materials for some applications. Further, we will facilitate grant-supported farmer-led outreach efforts, including field days and educational videos that allow growers to share their valuable insights regarding sustainable farming practices and alternatives to agricultural plastics with other farmers. This producer-centric approach to researching mulches is vital to not only understanding the potential positive/negative ecological and economic impacts of traditional and alternative mulches but also will empower sustainable agricultural practices throughout Western Oregon farming community and beyond. Additionally, we expect that this work will extend and be applicable to organic farms throughout the larger PNW region, including Northern California. Dissemination of project design and results will be achieved via the Pacific Northwest Consortium on Plastics, an already established network that reaches professional across sectors across the U.S. This research is in close alignment with a recent FAO global call for action and supported by Oregon lawmakers, with a goal of reducing infiltration of plastics into food systems and curbing the overall harm of plastics to human and environmental health.

Research objectives: 1. Design and run field studies in cooperation with producers from four Willamette Valley organic farms that compare traditional (LDPE), bio-based (PBAT, starch based plastic, e.g. BIO360), paper-based and wool mulch sheeting on active farms with vegetable or fruit crops to measure potential positive and negative impacts on soil health, moisture retention, and crop yield, microplastics breakdown, and organism uptake 2. Run controlled studies in a campus lab / greenhouse microcosm setting that compare the same four mulch types and responses, but also include a dose-response evaluation of MP uptake and impacts on important soil denizens (earthworms, nematodes), and 3. Collect data for conducting a cost-benefit analysis in order to assess the feasibility of switching to potentially more sustainable alternatives. Our work is supported at the state and federal level, and aligns with WSARE priorities because moving to more sustainable materials with fewer impacts on crops and surrounding ecosystems would enhance the quality and productivity of soil while conserving natural resources and improving the quality of surface and ground water. Along these same lines, using less toxic materials in mulching would also protect the health and safety of farmers and consumers.

Education objectives: 1. Producers at our four cooperating farms will educate scientists on their practices during the first year of the grant and work together to run field trials in preparation for the full field season in 2026. Because this is a sensitive matter, given that the use of alternative mulch materials may influence crop yields and thus profitability of farming operations, researchers have built in a period during the first year of the project for farmers to educate team members on the challenges and needs for each of their businesses. Approval of this approach that includes the opportunity for team-building and information gathering prior to deployment of field plots arose from discussions at a Plastics from Farm to Table workshop held by Brander and colleagues in September 2024. 2. Towards the end of second year of the project when mulch of four different types (traditional, bio-based, paper-based, wool) has been deployed for approximately one year, we will begin to coordinate and offer field day events at each of the four farms and invite farmers from the region to participate in a demonstration of how to deploy and maintain different mulch types as well as a discussion of potential differential impacts on moisture retention, material durability, and weed penetration, how these factors relate to overall crop health and yield, and the feasibility of wider implementation and use of alternative mulches. 3. This will stem from the second objective, in that the OSU graduate student and undergraduate assistant(s) will visually record farmer-to-farmer field day events (with the permission of growers) to produce an educational video intended for farmers who were not able to attend or who have a general interest in learning more about alternative mulches. This video will be a compilation of the events held at the four different farms and will be made available for free on our project website, with permissions obtained from anyone in the videos prior to sharing them, and also shared through social media channels already established by the Pacific Northwest Consortium on Plastics, which has been active since 2019.