Assessing the Biosafety of Chitosan‐Based Nanohybrid Fertilizers: A Multitropic Toxicological Study for Sustainable Agriculture

The study evaluates the biosafety of a novel chitosan-based nanohybrid fertilizer (NHF), formulated with poly (methacrylic acid) (PMAA) and encapsulating NPK and micronutrients (Fe, Mg), across multiple trophic levels to assess its suitability for sustainable agriculture. Following OECD guidelines, the eco-toxicological impact was tested on terrestrial organisms (earthworms: Eudrilus eugeniae; pollinators: Apis cerana indica, Trichogramma chilonis), aquatic organisms (fish: Poecilia reticulata), and beneficial microbes (Bacillus subtilis, Trichoderma viride, Pseudomonas fluorescens). No mortality was observed in honey bees or fish across all NHF concentrations (1%, 1.5%, 2%), indicating high biocompatibility. Earthworms exhibited near-100% survival and significant growth (weight and length increases) across treatments, suggesting no acute or sublethal toxicity. T. chilonis showed high adult emergence (88%-96%) and parasitisation efficiency (87%-94%), classified as "harmless" per IOBC standards. Microbial assays revealed dose-dependent effects: B. subtilis and T. viride exhibited reduced growth compared to controls, but NHF treatments were less inhibitory than chitosan alone, with T. viride recovering to control levels by 96 h. Cytotoxicity assays (LDH, MTT) on P. fluorescens indicated lower cell death and higher viability at higher NHF concentrations, attributed to nutrient enrichment. These findings highlight NHF's minimal ecological impact and compatibility with sustainable farming, offering a safer alternative to conventional fertilizers while supporting soil health, pollination, and aquatic ecosystems.