Preparation and characterization of slow-release and water-retention fertilizer based on starch and halloysite

In this work, a kind of slow-release and water-retention fertilizer was fabricated by free radical copolymerization of potato starch, acrylic acid, acrylamide, and β-cyclodextrin modified by maleic anhydride, accompanying halloysite nanotubes whose cavities were enlarged by acidification and loaded with urea in advance. The fertilizer was characterized by FTIR, TGA, SEM, TEM, and XRD. Its swelling behavior in distilled water and salt solutions as well as the ability to hold water was studied by weighing method. Finally, its controlled-release behavior to urea was investigated. The results suggested the as-prepared fertilizer had good abilities to retain water and control urea release. Moreover, the addition of halloysite helped to improve the release properties of the fertilizer. The study on urea release kinetics indicated the release behavior of urea in water was controlled by its concentration, whereas the release behavior of urea in soil fitted with Fickian diffusion mechanism. • Fertilizers were obtained in urea solution by radical polymerization • Fertilizers were based on starch, halloysite nanotubes and β-cyclodextrin • Halloysite nanotubes could load more urea by acidification • The fertilizers have the properties of slow-release and water-retention