Inhibition factors and soil contamination by macro/micro-particles related to biodegradation of mulching films in Mediterranean and northern climates

• Inhibition to mulch films’ biodegradation affects soil pollution by micro-particles • Low temperatures & acidic soil impede biodegradation rates in northern climates • Biodegradation in Mediterranean zone inhibited by material composition deviation • Few micro-particles in soil from biodegradable film irrespectively of climate zone • Many micro-particles from film with composition deviated from the certified one Key knowledge gaps for the biodegradability in soil of bio-based biodegradable mulching films include potential inhibition factors related to different climate zones, environmental conditions, and material composition. Possible soil pollution by macro/micro/nano-particles of the degraded mulching films has also been poorly investigated so far. These gaps, stemming from the lack of comprehensive, full-scale comparative studies, were addressed by examining the disintegration behaviour as an indication of biodegradation of two commercially available agricultural mulching films. Both films were manufactured from the same starch/PBAT-based raw material and certified as soil biodegradable. One type was tested under field conditions in southern (Greece) and northern (Finland) Europe, while the second type was tested in southern Europe (Italy). In Greece, the film fully disintegrated in 5-7 months, while in Finland, two dominant inhibiting factors suppressed its disintegration to 32% in 29 months: a) lower temperatures throughout the year (Twinter<0°C), and b) acidic soil, impeding the microbial activity. The disintegration of the second film type in Italy, under analogous climatic conditions to Greece, was significantly lower (84% in 29 months), because of an analytically identified deviation of the film’s composition. The analysis of the soils revealed a low number of micro-particles originating from the biodegradable film exposed in Greece and Finland. Macro, and mainly micro-particles originating from the mulching film exposed in Italy, were identified, confirming the inhibition effect of the material. New grades of soil biodegradable materials, designed to be functional and biodegradable under different climate zones and soil environments, should be urgently developed.