Green synthesis and slow-release mechanism of biodegradable compound fertilizers

N-(n-Butyl) thiophosphoric triamide (NBPT) degrades gradually when directly blended with compound fertilizer, which severely limits the product's shelf life. To address this limitation, a biodegradable coating layer composed of ethyl cellulose and stearic acid was applied to the surface of compound fertilizer granules via the solvent evaporation method, using industrially recyclable toluene and isopropanol as solvents. This approach enabled the stable integration of NBPT into compound fertilizers while maintaining its bioactivity. Incubation experiments demonstrated that the degradation rate of NBPT in the slow-release system compound fertilizer (SRS-CF) was reduced to 15.51% after 60 days of storage at 10°C, with a half-life of 221 days, in comparison with 17.9 days for directly adding NBPT to compound fertilizer. This study effectively addresses the technical bottleneck of the unstable incorporation of NBPT in compound fertilizers and provides feasible strategies for its practical application in compound fertilizer systems.