Slow Release of Dissolved N-Urea as NH4+ and NO3- Following Activated Carbon Application in Andisols Soil

Abstract

Urea is fertilizer that has low efficiency absorption in soil-plant system, which is about 30-50%. This is due to highly hygroscopic nature of urea that made urea dissolve easily into groundwater as nitrate when it applied to plants. Slow release fertilizer releases essential nutrient contained in urea slower than original urea fertilizer. Agriculture waste could be used as activated carbon which used to coat the urea in order to make slower release. The activated carbon in this study functioned in two different ways, as a coating material for the urea and as an adsorbent of urea residue. The research aimed to compare decreasing efficiency of dissolved urea as NH4+ and NO3- in Andisol soils using four activated carbon materials: coconut shells, rice hulls, corn cobs, and palm empty bunch during incubation period of 30 days. The result pointed out that the activated carbon could decrease NH4+ and NO3- dissolved in soil about 4-44% as compared with the control soils. It also showed that the activated carbon was the most effective in decreasing dissolved NH4+ and NO3- were those derived from coconut shells and rice hulls.