Ginger-extracted oil as an alternative for the emulsion to prepare chitosan microspheres for urea controlled-release fertilizer

The present study was undertaken with the aim of evaluating the ginger essential oil potential and its urea-loading efficacy in the preparation of control-releasing chitosan microspheres. The ginger oil for hydro-distillation was extracted by applying Clevenger apparatus, chemical composition was characterized by FTIR, and the GC-MS was used to identify the oil compounds. Urea-loaded chitosan microsphere formulations were formulated through modified emulsification and cross-linking procedure. The various factors and levels related to preparation of urea-loaded chitosan microspheres were evaluated using response surface test. The present study was also an effort to observe the yield and content of nitrogen. Additionally, FTIR and SEM were applied to characterize the microspheres. The results show the yield of ginger oil as 6.0%. Main compounds identified by GC-MS were gingerol, decanal, isoshogaol, octanal, and others. FTIR also showed that some typical bands appeared in ginger oil. The nitrogen content % in urea-loaded microspheres showed a significantly higher value in proportion to higher oil volume and cross-linking. However, by decreasing the amount of urea and enhancing acetic acid, nitrogen content was decreased. The lower oil concentrations improved the microsphere surface structure and morphology. Response surface analysis showed that the optimum preparation conditions are as follows: 2.094% of Span 80, 2.302% of acetic acid, and cross-linking agent ratio of formaldehyde to glutaraldehyde 1:8.15. Under these conditions, the theoretical value of nitrogen content of urea-loaded chitosan microspheres was 4.683%. According to release test, the urea diffused uniformly in the microspheres after 48 h. It is concluded that the use of ginger oil in control release of fertilizers is the right option in the formulations of control-releasing micro-fertilizers.