Biodegradable oil-based polymeric coatings on urea fertilizer: N release kinetic transformations of urea in soil

Polymer coatings are used to control the rate of release of plant available nutrients from fertilizers as well as to reduce nutrient losses such as ammonia (NH3) volatilization. Although the literature presents several examples of materials used to coat urea, little is known about nitrogen (N) release properties such as the mechanism involved and phenomena (e.g., pore opening) in the polymer coating. Thus, this study investigated urea release from polyurethane (PU) derived from two renewable raw materials (castor oil and soybean oil), to explain how the oil structure and coating microstructure influence release and urea-N dynamics in soil. The results demonstrated that the profile of urea release and the urea-N mineralization in the soil could be controlled by altering the thickness of the coating on the urea granules. Coating by eco-friendly polymer was efficient in controlling urea release in soil to reduce volatilization of ammonia and increase the availability of N in the soil.