Preparation and Properties of Urea Slow-Release Fertilizer Hydrogel by Sodium Alginate-Gelatin Biopolymer

Urea is high solubility nitrogen fertilizer. There is major nitrogen pollution in ecosystem. Slow-release nitrogen fertilizer the way to decrease nitrogen form agriculture. Slow-release nitrogen fertilizer the way to decrease nitrogen in agriculture. Slow-release formulations of nitrogen fertilizer were developed based on alginate-gelatin by using calcium chloride as the cross-linker in the egg-box model as hydrogels. Water-retaining ratio, loading behavior, and the release kinetics were examined. The release kinetic rates were investigated by Zero-order kinetic, First-order kinetic, Higuchi, Korsmeyer-Peppas, Weibull, and Hixson-Crowell models. The results showed that the S1G0.5 sample (alginate 1 g and gelatin 0.5 g) was the optimum condition for application as urea slow-release fertilizers because it was a minimal release kinetic rate for 12 hrs. These results indicate that the alginate-gelatin hydrogel can be a slow-release nutrient to plant an environmentally friendly fertilizer.