Study On Modification Of Chitosan As Sustained-release Fertilizer Vector

unique chemical structure and extensive sources. Because of its excellent biocompatibility, biodegradability, film forming ability, antibacterial activity and other excellent properties, chitosan has been popularly used in medicine sustained-controlled-release system. However, there is very few report about using chitosan as a sustained-release vector of fertilizer. As a sustained-release vector of fertilizer, chitosan not only can extend the release time of ferilizer, restrain and resist bacteria, but also be easy to degradate. Meanwhile, it has an advantage of non-residual and non-pollution. It is topic research in the agricultural in the future.In this paper, chitosan using as a sustained-release material was mainly discussed. Urea-chitosan films and urea-chitosan microspheres were prepared. Chitosan was modified by glutaraldehyde as the cross-linking agent. Then sustained-release chitosan films were prepared by solution cast method. The release films were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, the test of water-absorption and cross-linking degree. The modified film's swelling was measured. The result showed that chitosan and glutaraldehyde had produced cross-linked structure and the reaction between them was good. Because of the addition of glutaraldehyde, the speed of water absorption of films had been improved obviously. Further, the stability of films increased. The cross-linking degree of chitosan films was normally over 60% with the highest being 85%. The dosage of cross-linking agent and molecular weight of chitosan had some influence in the cross-linking degree. The result of the release experiment showed that as a sustained-release vector, chitosan could effectively achieve the purpose of sustained-release. But the speed of release was quick correspondingly. After 24 hours, the cumulate release of nitrogen element was over 90%, and the release tended to the end.Then urea-chitosan microspheres were preparaed by emulsification-chemical crosslinking method. The release mircospheres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and the test of cross-linking degree. The result showed that urea was successfully encapsulated in chitosan microspheres. Products presented a normal sphere with the diameter around 1μm. The structure of microspheres was impoved by adding porogenic agent. Some pores were found on the surface of microspheres. The volume of microspheres were increased, and the diameter was between 50μm and 120μm. The cross-linking degree of chitosan microspheres was over 89% with the highest being 97%. The result of the release experiment showed that the cumulate release of nitrogen element was inversely proportional to the chitosan concentration and the dosage of cross-linking agent. Compared with the result of release experiment with two release fertilizer, the release speed of chitosan micropheres was slower than the chitosan film. It indicated that the sustained-release microspheres have good sustained release effect.