A one-step surface modification technique improved the nutrient release characteristics of controlled-release fertilizers and reduced the use of coating materials

Controlled-release fertilizers (CRFs) are a valid solution to agriculture's nonpoint source pollution problem. Due to surface structural defects in the fertilizer core, however, a large amount of coating material was wasted. A simple, fertilizer surface modification technique (SMT) that is based on abrasives was created in this study to modify the micro/nanostructure of the core surface, thereby considerably minimizing the amount of coating material and ensuring precise and long-term nutrient release. The effects of the SMT on the surface structure, roughness, and roundness of fertilizer cores were investigated, and a finite, element-based, interface polishing removal kinetic model and a discrete element, simulation-based, two-phase, fluid dynamics model were developed. The effect of core surface structural defects on the coating formation of CRFs and the controlled-release behavior of nutrients was observed at the micro- and nanoscale. The SMT improved the formed weak interfacial layer structure by urea crystals adsorbing water vapor, by reducing surface roughness by 64.43%, by improving overall particle fluidity, by increasing the proportion of urea with high roundness (0.950-0.975) by 8.72%, and by lessening the surface area of a single particle by 2.18%. At high temperatures, the surface was softened and deformed, allowing for the reconstruction of the surface microstructure and for a considerable improvement in interfacial bonding performance. The CRF nutrient release characteristics showed that the SMT enhanced the tightness and consistency of the coating, improved the precision of nutrient release, and reduced the use of coating material by up to 28.6% during the same release period. This novel technology has the potential to significantly optimize the production of CRF by reducing coating materials and residues in soil generated after nutrient release.