This document is intended to openly disclose relevant information with the stakeholders of the PAPILLONS project with respect to the large-scale pan-European experiment that will be carried out between 2022 and 2023. The aim of this experiment is to study the potential effects of mulching film residues on soil ecosystems and their agricultural production. By presenting the experimental design in advance, PAPILLONS offers stakeholders the possibility of commenting and providing feedback and ideas prior to execution. These will be considered if they contribute to add quality, meaningfulness and objectivity to the experiment, and if their implementation is technically and economically feasible.
The main objective of the experiment is to address the following question:
Do legacy micro- and nanoplastic fragments accumulated in soil from deteriorated or partially degraded mulching films have an effect on farmed soil ecosystems and on soil fertility?
The experiment will be simultaneously and consistently conducted in three European countries: Spain, Germany and Finland. The same two microplastic materials will be separately tested at all sites (polyethylene (PE) mulching film fragments and biodegradable (Mater-bi- based) mulching film fragments), using soil cultivated with the same crop, and applying the local farming practices. Fragments will be obtained through cryomicronization of new films or from pellets made of recycled commercial films. The selection of the materials is performed by qualified experts with agronomy, polymer science and engineering background on the base of the material likelihood to represent a source of plastic fragments to soil. The ecotoxicology team involved with the assessment of effects and in running the experiment was not directly involved in this choice.
The experiment will be conducted in five fully randomized blocks that include one control and two concentration levels per each microplastic type. These concentration levels represent a worst-case scenario (75 g of plastic fragments per square meter of soil, equivalent to 0.05% of plastic in the soil ploughing layer) and an intermediate exposure scenario with (15 g per square meter, or 0.01%) for each type of material. The worst-case scenario is defined based on earlier observations of soils contaminated with polyolefin mulching film fragments. It also roughly represents a situation in which an entire film is mixed in the form of microplastic in a unit surface of soil, which is a relevant scenario also for the biodegradable film.
We offer the stakeholders the opportunity to give feedback on the exposure scenario and the treatment levels.
The experiment will take place over two years, but the plastics will be added to the soil only at the beginning of the first growing season. Several endpoints will be monitored during the growth and post-harvest periods to study possible mid- to long-term impacts of plastic fragments on soil ecosystem health and soil fertility. The endpoints measured will relate to a broad range of aspects such as agricultural performance, crop yields, soil properties and functioning and the health and functioning of soil invertebrates and microbiota.
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Deadline for feedback: March 6.