Ionically crosslinked Sodium alginate – Galactoxyloglucan hydrogel beads as a controlled release system for sustainable urea delivery

Abstract

The prolonged usage of chemical fertilizers often causes deleterious effects on the environment, and it remains an alarming issue in agricultural practices. Smart delivery of fertilizers achieved by hydrogels proved their efficiency in reducing risk in action. In this study, we investigated the optimization of urea-encapsulated hydrogel formulations and evaluated their physical and chemical attributes for agricultural applications. The proposed hydrogel formulation consists of ionically crosslinked two promising plant biopolymers (galactoxyloglucan and sodium alginate) which are specifically developed for the controlled release of urea fertilizer. The FT-IR analysis of the hydrogel beads confirmed the presence of biopolymer functional groups and urea. XRD analysis indicated the amorphous nature of the biopolymers. TGA revealed a thermal stability of up to 350°C. SEM images showed the porous structure of the hydrogel beads. To investigate the controlled release of urea, two kinetic models were employed: Korsmeyer-Peppas and Peppas-Sahlin. The results indicated a controlled release mechanism. The hydrogel beads demonstrated excellent water retention properties, maintaining soil moisture for up to 16 days. Additionally, degradability results demonstrated that in the soil environment, the hydrogel beads were degraded completely in 21 days. Therefore, we are confident that the formulated hydrogel bead exhibits eco-friendly and bio-compatible characteristics, which potentially mitigate the risks associated with urea fertilizers.