A mathematically tractable model for controlled-release urea fertilisers

The dissolution of polymer-coated, controlled-release urea fertilisers by means a simple, Fickian diffusion-based model is described. This in contrast to prior contributions that invoke non-Fickian mechanisms or take more quantitative view. Within quasi-static approximation, simple expressions for the granule radius and release profile as function time are obtained terms experimentally accessible parameters. Predictions compare well with available experimental data, although full required capture gradual saturation released late stages process. If scaled appropriately, wide range data different coatings turn out collapse onto what all intents purposes can be called universal curve. suggests extensive testing avoided if properties coating known beforehand.