Biostimulants for Sustainable Agriculture: The Evaluation of Crops Productivity and Soil Microbial Diversity - Biostimolanti per un’agricoltura sostenibile: la valutazione della produttività delle colture e della diversità microbica del suolo

The increasing demand for sustainable agricultural practices has accelerated the search for effective alternatives to synthetic agrochemicals. Among these, biostimulants of natural origin represent promising tools for enhancing crop productivity, stress tolerance, and disease resistance while reducing environmental impacts. This thesis, developed within the project BIO4.0AGRIFOOD - Robotization of biomass biotransformation screening for the identification and commercialization of high value-added bioactive products, investigates the agronomic and biological effects of selected biostimulants on rice (Oryza sativa L.), maize (Zea mays L.), and lettuce (Lactuca sativa L.). The study specifically focused on formulations derived from Trichoderma asperellum Samules, Lieckf & Nirenberg, hydrolysed seaweed extracts, and chitosan, comparing their efficacy against conventional treatments such as chemical fungicides and full nitrogen fertilisation. Field experiments were conducted under Mediterranean agroclimatic conditions in Italy from July to November 2023, using replicated plot designs. Treatments were assessed under both optimal and stress-prone environments, incorporating reduced nitrogen inputs to simulate ecological farming practices. Parameters monitored included chlorophyll content (SPAD values), biomass accumulation, disease incidence, and yield performance. Particular attention was given to rice blast disease (Pyricularia oryzae Cavara), evaluated using standardized IRRI scoring scales at multiple growth stages, alongside complementary laboratory assays for fungal identification and pathogen suppression. The results highlighted that biostimulant applications improved plant physiological responses, enhanced resistance to both biotic and abiotic stresses, and reduced dependence on synthetic inputs. Trichoderma asperellum displayed dual functionality as a biocontrol agent and growth promoter, while seaweed hydrolysates and chitosan demonstrated significant roles in stress mitigation and nutrient efficiency. These findings underscore the systemic benefits of naturalorigin biostimulants, not only in improving crop yields but also in contributing to soil health and long-term sustainability. The research reinforces the potential of integrating biostimulants into mainstream agricultural practices as a viable pathway toward environmentally responsible and resilient food systems. Keywords: Biostimulant, Rice, Maize, Lettuce, Trichoderma asperellum, Biomass, Rice Blast