Efficient release of urea with amorphous silica from pumice rock

Urea is a nitrogenous fertilizer usually applied for optimum production; nevertheless, nearly 50% is lost before utilization, resulting in poor yields and severe environmental pollution. As a result, controlled-release urea fertilizers are emerging to reduce nitrogen loss from highly soluble traditional urea fertilizers. Most controlled-release urea coatings emanate from costly or non-biodegradable polymers, which present ecological hazards. This study explored the feasibility of silica derived from pumice rock as a coating material for controlled-release urea. Silica was successfully extracted from pumice rock via alkaline leaching and characterized as amorphous with a high purity of 96.32%. Release studies showed that silica-coated urea significantly prolonged nutrient release, delivering 78% of urea over 5 days, compared to uncoated urea, which released the same amount within 24 h. These findings demonstrate that silica derived from pumice can serve as an effective, biodegradable coating material, offering a promising alternative to costly and environmentally harmful polymer-based coatings.