The process protocol for the synthesis of two slow-release nitrogen (N) fertilizers, namely ureaformaldehyde
polymer and urea-hydroxyapatite composite, was standardized and successfully produced. Incorporation of urea-formaldehyde into the hydrogel matrix led to an additional decrease in water absorbency, making the overall water absorbency of the slow-release fertilizer very low. Subsequently, an alternative approach was adopted to link the hydrogel polymer with a slow-release fertilizer, specifically Magnesium (Mg) doped urea-hydroxyapatite composite, through the wet granulation process. After testing various combinations of binding agents and different proportions of component materials, a polymerembedded slow-release nitrogen fertilizer having N content of 16% and a water absorbency of 171.12 g/g was developed.
