Biodegradable mulch films exhibit slower-than-expected degradation with negligible effects on soil microbial...

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Biodegradable plastic mulch films (PMFs) are increasingly used as sustainable alternatives to conventional films.
• Concerns exist that current biodegradability standards may not accurately reflect real-world in-field conditions.
• The accumulation of intact PMFs in soil and their effects on soil microbial communities remain largely undetermined.

Purpose of the Study:

• To investigate the in-field degradation of conventional and biodegradable PMF blends over 12 months in a temperate climate.
• To assess the impact of PMFs on soil properties and soil microbial community structure.
• To evaluate the fragmentation and degradation rates of PMFs under natural conditions.

Main Methods:

• A field experiment was conducted over 12 months in the UK.
• One conventional and seven biodegradable PMF blends were analyzed for degradation.
• Soil properties and microbial community structure were monitored.
• Above and below-ground degradation and fragmentation were assessed.

Main Results:

• PMFs exhibited no significant effect on soil properties or microbial community structure.
• Exposure time and meso-/macrofauna interactions were the primary drivers of bacterial and fungal community changes.
• Buried PMFs showed no fragmentation, irrespective of fauna presence, leading to stable microplastic concentrations.
• Degradation rates were slower than anticipated by current standards.

Conclusions:

• Current biodegradability standards for PMFs may be inadequate as they do not fully represent in-field degradation processes.
• The slow degradation and lack of fragmentation highlight potential long-term accumulation issues.
• Reframing biodegradability standards to consider degradation as a complex system property is crucial.