Effects of coating properties of controlled-release fertilizers on nutrient release characteristics

In order to study the effects of properties of coating materials on nutrient release characteristics of controlled-release fertilizers, the experiments concerning tensile testing, electronic microscope scanning and nutrient release rate in water were conducted on mechanical properties and micro-structure of two coating materials, and nutrient release characteristics. The results showed that the coating mechanical properties of thermoplastic resin P₂ were superior to that of thermoplastic resin P₁, by contrast, the permeability of thermoplastic resin P₁ was better than that of thermoplastic resin P₂; besides, thermoplastic resin P₁ tended to crack under the same conditions. However, the controlling capacity of two coating materials can't be achieved only by altering the coating rate. The results also showed that adequate amount of macromolecule water-repellent materials and adequate amount of degradable starches added to different coating materials could markedly improve mechanical property and microstructure, and thus control nutrients release rate. Accordingly, controlling capacity of nutrients in controlled-release fertilizers could be achieved by changing its coating rate and proportion of additives, the relation between them could be simulated by functions, and simulation equation achieved significant levels.