Biodegradable mulch films (BDMF), composed of the synthetic polyesters polybutylene adipate-coterephthalate (PBAT) and polylactic acid (PLA), are heavily used in Swiss agriculture. After use, these films are ploughed into soils to be mineralized by microorganisms. Yet, there is currently no data on the biodegradation of BDMF in soil under field conditions, leaving the possibility that biodegradation is much slower than predicted by laboratory incubations.
This proposal seeks funding for one PhD student to address essential open research questions and significant knowledge deficits related to the fate of BDMF in field soils. The proposed research will provide first reliable experimental data on the biodegradation dynamics of the major BDMF commercially available in Switzerland.
To this end, long-term soil incubations of BDMF under field conditions, in greenhouse mesocosms and in the laboratory will be conducted with periodic quantification of residual PBAT and PLA in soil. These incubations will be complemented by quantifying film-derived PBAT and PLA in field soils at a farm in the Kanton Zurich, which has been using BDMF for now three years. In addition to quantifying PBAT and PLA in soils, the project will assess mulch-film induced changes in the soil microbial community composition, both in bulk soil (to assess effects on the soil microbiome) and on the film surfaces (to characterize microbial BDMF degraders). The project results will inform farmers, authorities and regulators on a sustainable use of BDMF in Swiss agriculture.