Optimizing Nanopriming Duration: Chitosan-Stabilized Iron Oxide Enhances Lettuce Seedling Performance and Cost-Effectiveness.

Climate change and nutrient limitations increasingly hinder seed germination and early seedling establishment, highlighting the need for sustainable enhancement strategies. This study evaluates a green nanopriming approach using chitosan-stabilized iron oxide nanoparticles synthesized via an aqueous, low-energy co-precipitation process that employs biodegradable chitosan and avoids hazardous reagents, fully aligning with green chemistry principles. Lettuce seeds were primed in a 1 ppm nanoparticle suspension for 2, 6, 8, 16, and 24 h to identify the optimal priming duration. Chitosan markedly improved nanoparticle dispersion and colloidal stability, producing a strongly positive surface charge (+35.5 mV) that enhanced nanoparticle-seed interactions. The 8-h priming treatment yielded the greatest improvements, achieving a germination rate of 96.67% alongside the highest shoot and root elongation and biomass accumulation. Longer exposures (16 and 24 h) reduced performance, suggesting potential overstimulation or early metabolic imbalance. These enhancements likely arise from improved iron bioavailability, nanoparticle stability, and stimulation of early metabolic activation. A pilot-scale cost assessment demonstrated excellent economic feasibility, with production costs of only $4.40 per 10-L batch, supporting scalability for agricultural use. Overall, optimizing nanopriming duration using chitosan-stabilized iron oxide nanoparticles offers a sustainable, economical, and environmentally responsible approach to strengthen crop establishment under stress.