Preparation and Nutrient Release Characteristics of Liquefied Apple Tree Branche-Based Biocoated Large Tablet Urea

Controlled-release fertilizers (CRFs) could improve crop yield and fertilizer use efficiency. However, the coating materials of conventional CRFs are mainly derived from petrochemical products, which are expensive and nondegradable, bringing potential environmental pollution. Therefore, using sustainable bio-based materials is the development direction. In this study, large tablet urea (LTU) was prepared using physical extrusion technology. The economical and biodegradable liquefied apple tree branch bio-based coating material was used to coat LTU, obtaining large tablet CRFs (LTCRUs). Also, the optimum proportion of liquefaction of apple tree branches modified by castor oil was studied. The specific surface area, surface morphology, and FTIR of LTCRU were characterized. The results showed that the surface of the LTCRU was the most smooth and the LTCRU modified with 30% castor oil presented the best controlled-release characteristics. The specific surface area of LTCRU was one-third of that of traditional small-particle fertilizers, which indicated that reducing the using dosage of coating materials is economical. Overall, this work provided theoretical and technical supports for the industrialization of biocoated superlarge tablet urea, which is conducive to the green development of agriculture.