This research aims to prepare liquid fertilizer beads formed with sodium alginate (SA) (SAB) that were coated with interpenetrating polymer network (IPN) hydrogels based on pre-vulcanized natural rubber latex (NR) and cassava starch (St) (IPN NR/St) for controlling the release of the urea solutions. The preparation of SAB at various concentrations of SA and calcium chloride (CaCl 2 ) solutions was investigated. It was found that the appropriate concentrations of SA and CaCl 2 solutions were 1.5 and 5.0 wt%, respectively. The obtained SAB was coated with IPN NR/St, the ratio between SAB and IPN NR/St at 1.0/1.0, and the number of coated layers of IPN NR/St at 2 layers. As a result, coated alginate beads (CSAB) can decelerate the release of urea solution, and enhance the Thai eggplant growth. Thus, the CSAB could enhance not only the release control of urea solution but also lesser environmental problems, and is a novel technique for coating and the liquid release control for organic or biofertilizers.