Chitosan nanoparticle-reinforced thermoplastic starch films for controlled release of NPK fertilizers and enhanced plant performance.

Thermoplastic starch (TPS) films were investigated as biodegradable matrices for the controlled release of nitrogen-phosphorus-potassium (NPK) fertilizers, with and without the incorporation of chitosan-based nanoparticles (NC). Films were prepared as TPS, TPS + NPK, and TPS + NC + NPK and characterized in terms of structural, physicochemical, thermal, and photodegradation properties. The incorporation of NPK and NC modified the organization of the polymer matrix, affecting water interaction, surface properties, and thermal stability. Leaching assays in soil demonstrated that TPS-based films promoted a more sustained nutrient release compared to conventional fertilization, following near zero-order kinetics. The presence of NC modulated nutrient dynamics, reducing nitrogen release while slightly enhancing phosphorus availability. Biodegradation tests revealed that NPK accelerated matrix degradation due to microbial stimulation, whereas NC improved structural stability and reduced degradation rates. Greenhouse experiments with cherry tomato plants showed that TPS-based systems, particularly TPS + NC + NPK, enhanced plant growth, biomass accumulation, and fruit production compared to controls. These results highlight the potential of TPS-based films reinforced with chitosan-based nanoparticles as sustainable platforms for controlled nutrient delivery, contributing to improved nutrient use efficiency and reduced environmental impact in agricultural systems.