EFFECTS OF COMPOST MADE FROM COMPOSTABLE BIOPLASTIC PACKAGING ADDED TO ORGANIC WASTE ON WHEAT HEALTH AND RHIZOSPHERE MICROBIOME: A FIELD EXPERIMENT

There is a growing global demand for innovative and sustainable bioplastic packaging to reduce the use of petroleum-based plastics. In line with the principle of a circular bioeconomy, the use of compostable bioplastics (BPs) can bring several benefits to composting and urban organic waste (UOW) management by reducing contamination with conventional plastics and enabling the production of compost that can be safely used in agriculture. However, the potential impact of the presence of BPs in compost on the soil microbiome and plant health needs to be assessed. This study aimed to evaluate and compare the effects of ’standard’ compost (Com) obtained from UOW and UOW composted with 3% BPs (Mater-bi) (BioP) on the health of wheat and its rhizosphere microbiome. Composting was carried out in a industrial composting plant under the supervision of the Consorzio Italiano Compostatori (CIC). In 2021-2022, field trials were carried out at an agricultural experimental station. Three treatments (Com, BioP and Ctrl) were tested with five replicates each. At the time of flowering, ten plants and the associated rhizospheric soils were collected from each plots. Morphological and productive wheat traits were measured. Bacterial and fungal communities were analysed by 16S and ITS metabarcoding. No significant differences between treatments were found for wheat traits. However, Com and BioP compost addition significantly changed the microbial communities compared to the Ctrl, although few taxonomic and functional differences were observed between the Com and BioP communities. However, network analysis revealed significant differences between these communities, with BioP showing a much more connected community compared to those of Com and Ctrl. Furthermore, the addition of compost, regardless of type, was able to select beneficial taxa involved in nutrient cycling and plant growth promotion. The results showed that adding BPs did not negatively affect the quality of the compost, neither the wheat nor the health of the soil microbiome. Thus, BPs may represent a valid and sustainable alternative to conventional plastics.