Abstract
Controlled-release fertilizers (CRFs) are increasingly developed to enhance nutrient use efficiency (NUE) and reduce leaching losses in sustainable agriculture. The objective of this study was to developed poly (vinyl alcohol) (PVA)/borate/chitosan hydrogels as a controlled release carrier for potassium chloride (KCl) nutrient. The hydrogel composition was systematically optimized and the formulation with a PVA: borate: chitosan volume ratio of 8:1:5 (with 1 mL of 1 M KCl) exhibited the best structural homogeneity and mechanical integrity. Fourier-transform infrared (FTIR) spectroscopy revealed hydrogen bonding interactions between PVA and chitosan, as well as possible ionic interactions between K⁺ ions and borate groups, contributing to network stabilization. Compared to PVA/borate-KCl CRF, the chitosan-modified system exhibited significantly higher swelling capacity (750.7% vs. 642.5%), prolonged water retention (234 h vs. 216 h) and a slower, more controlled nutrient release profile. Kinetics analysis showed that the release behaviour was fit described by second-order kinetics model, indicating that the rate-determining step of the release process is the hydration of the ions in the system. The improved performance of the CRF might be attributed to increased network compactness, enhanced intermolecular interactions and higher diffusion resistance within the hydrogel matrix. These findings demonstrated that the incorporation of chitosan effectively enhances both structural stability and release kinetics control of PVA/borate hydrogels, highlighting their potential as environmentally friendly matrices for sustainable potassium fertilizer delivery.
Keywords: Agrochemical, Chitosan, Controlled-release Fertilizer, Hydrogel, PVA/Borate/Chitosan-KCl.