Preparation of green hydrogel for slow-release urea and its positive effect on improving wheat yield under deficit irrigation conditions and remediation of soil

Due to the rising costs, environmental concerns, and limited availability of conventional fertilizers, developing eco-friendly, multi-functional fertilizers is crucial for sustainable agriculture. This study introduces a cellulose-based superabsorbent polymer (SAP) as a carrier for controlled-release urea fertilizer. The resulting cellulose-based slow-release fertilizer (CSRF) effectively absorbs and retains water, enabling gradual urea release. The performance of CSRF was evaluated under various conditions. Water absorbency kinetics followed Fickian diffusion in saline solutions, whereas non-Fickian diffusion was observed in distilled water. The impact of pH on urea release was investigated, and the Korsmeyer-Peppas model accurately described the release kinetics in all pH environments. Column leaching experiments demonstrated a significant reduction in urea leaching, also 61.46 % of the urea was released over 42 days in soil. Furthermore, CSRF exhibited biodegradability in soil, with 43.73 % degradation after 60 days. The polymer also showed good reusability in both distilled water and saline solutions. Pot experiments confirmed the positive impact of CSRF on wheat growth under water-stress conditions. Increased chlorophyll content in wheat leaves further highlights the potential of CSRF to enhance plant health and yield. These findings suggest that CSRF can contribute to sustainable agriculture by improving water use efficiency, reducing fertilizer loss, and promoting plant growth. • CSRF fertilizer is a cost-effective alternative to traditional fertilizers. • CSRF increases wheat growth in water-deficit conditions by retaining moisture. • CSRF reduces fertilizer consumption by reducing urea leaching by 10 %. • The urea release at different pH levels corresponded to the Korsmeyer-Peppas model. • CSRF degrades by 43 % after 60 days and is environmentally friendly.