| dc.description.abstract | Onggok is a byproduct of tapioca production from cassava. Onggok contains 73% of starch which is potential to be transformed into soil conditioner, i.e. hydrogel to control urea release rate. Onggok was copolymerized by grafting with Na-acrylate, ammonium persulfate as initiator, and N,N-methylene-bis-acrylamide as cross-linker to produce onggok-g-polyacrylate hydrogel. Swelling of the hydrogel in water and 1 M urea solution were 250 and 203 g/g, respectively. The amount of urea that could be loaded into the hydrogel 1 M urea solution was 99%. Urea release rate from hydrogel in water followed a sigmoidal pattern, i.e. Richards model with correlation coefficient of 0.997. This hydrogel could inhibit the urea release in water 8.2 times higher compared with conventional urea application. Biodegradation of 0.11 g of hydrogel in 250 g of soil produced 754 mg of CO2 in 29 days so that it can be used in soil for more than 1 month. | en |
