Synthesis, characterization and analysis of biodegradable polymer-coated urea fertilizers for controlled nutrient release

The study aimed to develop a highly efficient, biodegradable polymer-coated urea to minimize nitrogen (N) losses and facilitate sustained release. The study included four treatments: T1: uncoated urea (UCU); T2: palm stearin-coated urea (PSCU) 10%; T3: pine oleoresin-coated urea (POCU) 6%; and T4: humic acid-coated urea (HACU) 15%. The bio polymer-based urea coatings were compared for their N content and their dissolution rate in water against UCU as a control. Results from high throughput instrumentation revealed that the coating materials had great compatibility with urea fertilizer. In a laboratory study of urea release in water over a 5-h interval, PSCU 10% (0.54–2.38 mol L−1) exhibited a sustained release of urea. This performance was superior to POCU 6% (0.59–2.50 mol L−1) and HACU 15% (0.71–2.69 mol L−1). In contrast, UCU released (1.61–2.47 mol L−1) almost all its urea within 2-h interval. Additionally, PSCU 10% had excellent synergy in surface morphology, interaction and crystal structure through scanning electron microscope (SEM), Fourier transform infrared spectroscopy analysis (FTIR) and X-ray diffraction (XRD), respectively. The PSCU 10% fertilizer could be a good competitor for other coated urea fertilizers. However, this fertilizer must be field validated to prove its effectiveness on crops before commercialization.