Modification of Gelatin Hard Capsules With Surface Crosslinking and Epoxy Resin for the Slow‐Release of Urea

ABSTRACT Here, we report the preparation of large‐sized gelatin capsules via a dipping method. The surface properties of the capsules were engineered via glutaraldehyde crosslinking and epoxy resin grafting to enhance hydrophobicity and crosslinking density. Soil column leaching tests with urea‐loaded capsules demonstrated an excellent sustained‐release profile, characterized by a low initial release (4.5% within 24 h) and prolonged nutrient release (78.4% over 28 days). Beyond improving fertilizer efficiency, this capsule system offers a versatile platform for co‐encapsulating multiple agrochemicals, such as fertilizers and pesticides. This work successfully bridges pharmaceutical capsule technology with the field of agricultural controlled‐release fertilizers.