Preparation on polymer-modified clay of alginate-saponite composite for urea slow-released fertilizer application has been conducted. The material was prepared by intercalating alginate into saponite structure followed by composite formation using urea. Material characterization was performed by x-ray diffraction, gas sorption analysis, and Fourier-Transform Infra-Red (FTIR) spectroscopy. Swelling, diffusion and network parameters of the composite were studied. The results indicated that the increasing physicochemical character was found as identified by the increasing basal spacing d 001 of saponite as well as increasing specific surface area after intercalation and composite formation. The increasing water sorption and urea adsorption rate were obtained by the modification. Study on the effect of pH on urea desorption rate composites showed that the kinetics are fit with Ritger-Peppas, first-order desorption and Higuchi models. The higher acidity enhances the rate of urea desorption. By Ritger-Peppas model, n values of desorption kinetics at all pH variation are at the range of 0.81-0.91 The values describe that the release mechanism is controlled by the diffusion and relaxation rate and it depends on water migration and urea diffusion.