Electrospun PVA/Urea Nanofibers as Morphology-Engineered Systems for Controlled Nitrogen Delivery in Agricultural Soils

Electrospun composite nanofibers represent an emerging strategy for the development of efficient fertilizer systems, as they enable modulation of the structural properties of the nanofibrous network and, consequently, the transport and release processes of nutrients. In this study, polyvinyl alcohol (PVA) nanofibers loaded with two different urea contents (0.09 g and 0.36 g) were fabricated and characterized to investigate how urea incorporation modifies the nanofiber morphology and influences urea release kinetics. SEM and EDS analyses confirmed that increasing urea content promotes surface roughnes and reduced nanofiber diameters, whereas XRD and FTIR demonstrated a decrease in crystallinity and the formation of hydrogen-bonded interactions between PVA chains and urea molecules, indicating that urea is incorporated within the PVA network rather than being superficially adsorbed on the nanofiber surface. These structural changes govern water retention and release kinetics: the 0.36 g formulation exhibited a 100-h induction period followed by multiphase diffusion, while the 0.09 g system displayed immediate release but lower final concentrations. Kinetic modeling revealed excellent fitting to the Higuchi and second-order models, confirming diffusion-controlled urea release modulated by internal interactions. The nanofiber network thus behaves as an active regulator of nitrogen mobility, overcoming the limitations of conventional coating-based fertilizers. These findings demonstrate the potential of PVA/urea nanofibers as scalable platforms for sustainable nitrogen delivery in agriculture, bridging morphology-driven polymer design with environmental performance.