Preparation and Application of Core–Shell Nanocarbon-Based Slow-Release Foliar Fertilizer

The application of nanotechnology offers a promising solution to improve fertilizer utilization efficiency by mitigating the losses and volatilization of conventional fertilizers, contributing to sustainable agriculture. In this study, a core-shell nanocarbon-based slow-release foliar fertilizer (CN@mSiO₂-NH₂@Urea@PDA) was synthesized using nanocarbon (CN) as the core, amino-functionalized mesoporous silica (mSiO₂-NH₂) as the shell, and polydopamine (PDA) as the coating layer. BET analysis revealed a 3.5-fold and 1.9-fold reduction in material porosity after PDA encapsulation, confirming successful synthesis. The controlled-release performance was enhanced, with a 24% decrease in the release rate and a prolonged nutrient delivery duration. Hydrophobicity tests demonstrated a 20° increase in the contact angle, indicating improved adhesion. Seed germination assays validated biosafety, while field trials showed a 69.94% increase in the choy sum (<i>Brassica rapa</i>) yield, 21.64% higher nitrogen utilization efficiency, and 22.21% reduced nitrogen loss. The foliar application increased the plant nitrogen use efficiency by 18.37%. These findings highlight the potential of CN@mSiO₂-NH₂@Urea@PDA as an advanced foliar fertilizer, providing a strategic approach to promote nanomaterial applications in agriculture and enhance the acceptance of functional fertilizers among farmers.