Nanocomposite of nanocellulose-bentonite for coating urea fertilizer: Towards reducing nitrogen nutrient loss

Excessive nitrate leaching in high-rainfall tropical regions significantly reduces fertilizer efficiency, negatively impacting crop productivity and environmental health. To address this challenge, this study developed a controlled-release fertilizer using a nanocellulose-bentonite nanocomposite coating to minimize nutrient loss. Cellulose was extracted from corn husk via alkali treatment and bleaching, followed by nanocellulose preparation through sulfuric acid hydrolysis. Bentonite nanoparticles (Bent) were synthesized via HCl activation and calcination. The nanocellulose-bentonite nanocomposite was produced at three ratios (1:1, 1:5, 1:10 w/w), with X-ray diffraction analysis confirming nanoparticle sizes of 3.788 nm, 7.064 nm, and 28.767 nm, respectively. Fourier-transform infrared spectroscopy confirmed successful nanocomposite formation, while scanning electron microscopy revealed uniform dispersion of bentonite within the nanocellulose matrix. Urea was coated with the composite via immersion, and ammonium (NH 4 + ) release kinetics was evaluated in both soil and aqueous media. Ultra violet-visible spectrophotometer was used to measure NH 4 + concentration in the leachate. Nitrogen release study demonstrated that nanocellulose-bentonite nanocomposite coated urea released only 20.47 % of NH 4 + after 11 days in soil media, compared to 63.13 % from uncoated urea. In water media, coated urea exhibited a gradual release of NH 4 + , reaching a cumulative of 64.72 % after 7 h, while uncoated urea released a cumulative of 27.27 % NH 4 + within the 7 h. The study highlights nanocellulose-bentonite nanocomposite as an effective, eco-friendly coating material for slow-release fertilizers, enhancing nutrient retention and reducing environmental pollution. Further field trials in acidic soils are recommended to validate agronomic performance and plant uptake efficiency.