Valorisation of residual biomass for soil health: from medicinal plants to the MaisPLUS Project for sustainable and circular agriculture

Growing interest in sustainable agriculture has been driven by increased awareness of the environmental impacts of conventional farming practices. The adoption of technological innovations and circular economy approaches in waste management can significantly improve efficiency and reduce the ecological footprint of practices such as improper disposal. In this context, the valorization of residual biomass represents a promising strategy: medicinal and aromatic plants (MAP), distilled for essential oil extraction, generate residues still rich in biocomponents, potentially usable as soil amendments. Metabarcoding analyses conducted on soil and root samples in field and greenhouse experiments on the use of residues as amendments have highlighted an impact on soil health, crops, and the assembly of microbial communities. This analysis demonstrates that prokaryotic communities are more sensitive than fungal communities to management practices and indicates the need for multi-year interventions for a stable restructuring of the soil microbiome. The MaisPLUS project, recently supported by the CRT Foundation, was born on this basis. It integrates multidisciplinary approaches to reuse various agricultural wastes from Piedmontese farms, particularly those belonging to the Associazione Antichi Mais Piemontesi (Piedmontese Antichi Mais Association). The project focuses on soils cultivated with native, non-hybridized maize varieties (e.g., Ottofile, Pignoletto, etc.), where processing residues from the maize itself and crops such as walnuts, hazelnuts, and vines will be applied as soil improvers. Through chemical, physical, and biological analyses, sustainable practices will be identified to improve soil biodiversity and reduce the use of synthetic inputs. Expected outcomes include the development of a soil "identity card" and a cost-benefit assessment of the practices adopted, contributing to the development of resilient, sustainable, and zero-waste-oriented agricultural systems.