Zeolite coated urea fertilizer using different binders: Fabrication, material properties and nitrogen release studies

Zeolite is the most widely used coating material in developing controlled release fertilizers (CRF) due to low cost and its inherent cation exchange property that effectively controls the nutrient release rate. Using an appropriate binder is the key in fabricating structurally stable zeolite based CRF due to the poor binding behavior of zeolite. In this research, five different binders, namely corn starch, potato starch, bentonite clay, white cement, and acrylic polymer were used in fabricating zeolite coated urea CRF using a pan granulator at different operational conditions. The fabricated CRFs (using five different binders) were characterized by particle size distribution (PSD), structural stability, crushing strength, elemental analysis, Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Nitrogen release rate from the CRFs was investigated by laboratory studies. The zeolite coated urea with acrylic polymer binder (UZ-AP) was found to be structurally stable with high crushing strength. The SEM analysis revealed that UZ-AP had dense coating and tiny pores with 135-150μm coating thickness. The FT-IR analysis predicted the hydrophilic nature of the CRF. The UZ-AP controlled the nitrogen release by 54.7% compared to other CRFs. Thirty days soil column study for UZ-AP and urea concluded that leaching of nitrogen decreased by 65% compared to urea fertilizer. This newly developed zeolite coated urea could be a potential nitrogen fertilizer with controlled release property for efficient crop nitrogen management.