A glance down any row of raised bed vegetable crops at most commercial farms reveals long plastic strips carefully fitted over the soil beneath the budding plants. The plastic film has long been a tool used by farmers to assist in the production of crops such as strawberries, squash, tomatoes and lettuce, as it helps warm the soil, conserves moisture, and reduces invasive weeds and pests, ultimately improving productivity.

More than a third of the country’s vegetables are grown in California, with crops such as strawberries equating to a $2.2 billion industry. However, those crops also generate a large amount of plastic waste: California farmers alone are estimated to dispose of over 55 thousand tons of plastic per year. In addition to agricultural plastic waste that is removed from fields and destined for landfills, fragments of the plastic materials that are inadvertently left behind in fields may have a long-term detrimental effect by contaminating the soils and water.

This research has direct implications for reducing the agricultural plastic waste stream and has garnered the interest from a number of producers currently using plastic in agricultural production.

— Seeta Sistla

Seeta Sistla, an assistant professor in the Natural Resources Management and Environmental Sciences Department who specializes in soil ecology and global change science, is researching ways to reduce the impact of the use of agriculture plastics, known as “plasticulture.” Sistla was awarded a $344,250 California State University Agricultural Research Institute grant to initiate a study of biodegradable plastic mulch as an alternative to conventional plastic in cropping systems. She is working in collaboration with researchers at San Francisco State University, Washington State University, the California Marine Sanctuary Foundation and the University of Tennessee.

“The maintenance of healthy soils is paramount to sustaining agricultural production, water quality, soil carbon storage, reducing terrestrial greenhouse gas emissions, and facilitating human health,” Sistla said. “The use of agricultural plastics has grown rapidly, and plastic now covers millions of acres of farmland globally.”

A group of Cal Poly undergraduate and graduate students are assisting with a wide range of field and laboratory studies, assessing the utility of biodegradable mulch in local strawberry cultivation and the effects of different plastics fragments on soil microbial decomposers. Students are investigating how commercially available biodegradable mulches, which are designed to breakdown in soil over time, compare with conventional plastic mulch in strawberry cultivation and how soil health is impacted.

The research is being conducted directly in the field in partnership with the Cal Poly Strawberry Center and through laboratory analysis of soils. “Plastic waste is a huge issue for the California strawberry industry, and any gains in the use of biodegradable mulch will be of great interest,” said Gerald Holmes, director of the Cal Poly Strawberry Center.

“Ultimately, I hope this research can help to inform growers who use plastic mulch if biodegradable alternatives are viable for their crops and reduce agriculturally derived plastic pollution,” Sistla said. “This research has direct implications for reducing the agricultural plastic waste stream and has garnered the interest of a number of producers currently using plastic in agricultural production.”


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