Plasticulture is contaminating agricultural fields

Oct. 22 () –

The use of plastic sheets for weed control, even with the best management practices, contaminates the soil with macro- and microplastics and negatively affects critical soil functions.

It is the conclusion of a study carried out by Ekta Tiwari and Seeta Sistla, from California Polytechnic State University, who took samples from 12 agricultural fields on the Central Coast of California. It was published in PNAS Nexus.

Worldwide, more than 10 million hectares of agricultural land are seasonally covered with opaque plastic films used as “mulch” to prevent weeds, retain moisture and warm the soil, a practice known as “plasticulture.” Most studies have evaluated the impacts of soil contamination from plastic mulch using laboratory-based models or experimental plots.

For the new study, fields were inspected after plastic mulch had been carefully removed for the season, a “best practice” to reduce plastic pollution in fields. However, all the fields studied had plastic contamination and the authors found up to 25 kg of macroplastic waste per hectare, covering up to 3.4% of the field surface. Microplastics were also found in all fields and microplastic concentrations were positively correlated with macroplastic concentrations.

Key soil health characteristics were negatively correlated with macroplastic accumulation even at relatively low pollution levels, while no relationships were detected with microplastic pollution. Therefore, current “best practices” are causing subtle but harmful effects on the soil.

As the use of plastic film is rapidly expanding globally, the authors suggest exploring a biodegradable, plastic-free alternative to limit the threat to soil function and agricultural productivity caused by the relentless accumulation of plastic.