Exploration of Shredded Cardboard as a Mulch and Compost Resource to Improve Soil Health and Water Management by Urban Growers in the Twin Cities

View the project report

Commodities

• Fruits: berries (strawberries)
• Vegetables: beans, collard greens

Practices

• Crop Production: municipal wastes, mulching
• Education and Training: demonstration, display, extension, farmer to farmer, on-farm/ranch research, participatory research, technical assistance
• Natural Resources/Environment: soil stabilization
• Pest Management: mulches - general, physical control, weed ecology
• Production Systems: urban agriculture
• Soil Management: nutrient mineralization, organic matter, soil analysis
• Sustainable Communities: leadership development, urban agriculture

Title: Exploration of Shredded Cardboard as a Mulch to Improve Plant and Soil Health in Urban Farms and Gardens in the Twin Cities Metropolitan Area, MN 

Problem Description: Mulching is utilized by urban growers to build soil health, mitigate weed pressure, and reduce water use. Despite these benefits, many mulching materials have become too expensive for growers to purchase and transport in the quantities required for an urban garden or farm. Our community-university research team identified shredded cardboard as a potential new mulch material that is accessible and affordable because of the increase in cardboard packaging for home delivery during the COVID-19 pandemic. The overall objective of this collaborative project is to assess the performance of shredded cardboard mulch in urban farms and gardens.

Key Outcomes:  Researchers, extension educators, and urban growers will increase understanding about the efficacy of shredded cardboard mulch and its impact on plant health, water use, and soil fertility. Researchers/educators will leverage grower experiences to develop mulching guidance and education resources. Growers will implement mulching practices to increase yields while stewarding environmental resources, such as water and soil nutrients.  

Approach: Activities were designed collaboratively by the community-university research team and informed by feedback from twenty growers who participated in a pilot study of shredded cardboard mulch in summer 2021. Growers observed that while mulch reduced weed pressure and maintained soil moisture, crops were more susceptible to chlorosis (leaf yellowing). Thus, we will conduct replicated research trials at the University of Minnesota to compare the effects of shredded cardboard mulch, straw, and no mulch on yield; nitrogen cycling; and soil characteristics (Activity 1). Based on grower interest in conducting research and requests for support to implement mulching, irrigation, and fertility management practices, we will facilitate complementary grower trials at six community gardens and facilitate co-learning gatherings to build shared knowledge (Activity 2). Finally, we will connect shredded cardboard mulching practices to broader environmental justice and climate change adaptation efforts by establishing an industry advisory panel, conducting a literature review, and facilitating three tours per year of sites such as cardboard production, recycling, and composting facilities, garden networks, or community organizations addressing climate change (Activity 3).

Relevance: In combination with parallel projects to explore local production and distribution of shredded cardboard, this project will contribute to increasing the availability, affordability, and accessibility of a new mulching option, which would benefit small-scale growers throughout the North Central Region.

Researchers, extension educators, and urban growers will increase understanding about the efficacy of shredded cardboard mulch and its impact on plant health, water use, and soil fertility. Co-learning gatherings will deepen relationships between researchers and growers; build shared knowledge; and increase grower capacity, all of which will support action outcomes (people). Researchers/educators will leverage grower experiences to develop mulching guidance and education resources. Growers will implement mulching practices to increase yields (profitability) while stewarding environmental resources, such as water and soil nutrients (planet). Participating in tours will highlight connections between research, grower practices, environmental justice, and climate change.