Part of the fertilizer nitrogen (N) appliedto pasture may be lost from the system and, in tropical pastures, the volatilizationof ammonia (NH3) is one of the major pathways of loss. The presentstudy aimed to estimate the NH3-N volatilization loss in Panicummaximum cv. Tanzania pasture fertilized with urea during the summer. A completelyrandomized design, following a repeated measure arrangement, with three replicateswas used. The plots were represented by urea levels (40, 80 and 120 kg/ha urea-N)and the subplots by the time after fertilization (1, 5 and 9 days). The interactionbetween level of fertilization and time after urea application was significantfor accumulated NH3-N volatilization loss and daily NH3-Nvolatilization loss rate. The combination of high soil water content, lack ofrainfall in the day following fertilization and high temperature determinedhigh ammonia volatilization losses. The accumulated NH3-N loss inthe period represented 48%, 41% and 42% of the applied N in 40, 80 and 120 kg/haurea-N fertilizations, respectively. The accumulated NH3-N loss (kg/ha)increased, while the daily NH3-N volatilization loss rate decreasedwith the increase in time after fertilization.
