Vegetable and fruit growers pay for a lot of plastic – $3.4 billion in worldwide sales in 2017. Farmers use plastic mulch to suppress weeds, retain moisture, prevent soil erosion, and increase yields. Disposal at the end of each growing season is a costly problem. Plastic mulches are stockpiled on farms, burned illegally, and/or transported to landfills. Conventional plastic mulch materials are not biodegradable and can persist in the soil for decades if not centuries. Residual pieces of plastic film remain in the soil, where they can form microplastics, damage soil, and may even enter the food chain.
To lessen the costly side-effects of conventional materials, USDA funded a team of scientists, engineers, and extension experts at the University of Tennessee Institute of Agriculture, Washington State University, and Montana State University to explore and verify biodegradable plastic mulches’ benefits and long-term impacts on soil, crop quality, and yield.
The partners investigated biodegradable plastic mulch to evaluate effects on soil health, crop production, pests, and diseases at two diverse geographical locations. They also assessed the economic costs and benefits for growers and consumers. They engaged stakeholders to increase adoption and developed important informational resources (see biodegradablemulch.org).
Over a four-year period, the team found no change of soil quality or microbial communities and no major differences in crop growth in two diverse regions using biodegradable compared to conventional plastic mulch. This is encouraging news for farmers as they protect their soil and profits.