Fabrication of a water-retaining, slow-release fertilizer based on nanocomposite double-network hydrogels via ion-crosslinking and free radical polymerization

•Double-network hydrogel beads were used as water-retaining and slow-release fertilizers.•The beads were fabricated via ion-crosslinking and the free radical polymerization.•The fertilizers contain sodium carboxymethyl cellulose, halloysite nanotubes and β-cyclodextrin.