Preparation of hydrophobic hard gelatin capsules for slow-release fertilizers

In order to attenuate the pollution problem caused by low fertilizer utilization, a biodegradable urea slow-release capsule was prepared in this study using gelatin as the main material. Glycerol was added to the gelatin solution as a plasticizer, and the mechanical properties and water resistance of the gelatin film were enhanced by crosslinking with glutaraldehyde. The addition of nano-SiO2 (nSiO2) and calcium magnesium phosphate fertilizer power (CaMgP) enhanced the hydrophobicity and tensile strength of the gelatin film. X-ray diffractometer confirmed that the nSiO2 could make the gelatin molecular chains more tightly entangled. Scanning electron microscope indicated that the addition contents of nSiO2 and CaMgP was optimal at 2 wt% and 40 wt%, respectively. The gelatin capsules were loaded with urea particles for slow-release experiments, the results of soil column drenching showed that the release rates of urea from nSiO2-modified and CaMgP-modified cross-linked gelatin capsules were 4.1 % and 5 % after 24 h, respectively, and 78.8 % and 75.2 % after 28 d, respectively.