Soil biogenic emissions of N20 and NO increase considerably when nitrogen fertilizer is applied to soils. Global nitrogen fertilizer consumption increased at 3.5% per year during the decade 1979 to 1989 [Matthews, 1994]. Most of this increase has occurred in tropical and subtropical regions. If fertilizer use keeps increasing at the current rate, it is expected that by 2025, 100 Tg yr -1 of N fertilizer will be applied in developing countries (according to a 1990 Environmental Protection Agency study cited by Matson et al. [ 1996]). Several reviews have summarized the effect of fertilizer use on N2O emissions in temperate climates [Eichner, 1990; Bouwrnan, 1994]. Current global N20 budget calculations are based on the assumption that fertilizer effects are of the same magnitude in temperate and tropical areas. However, a recent study by Matson et al. [ 1996] showed that the percentage of applied urea that was emitted as N20 was higher in a tropical climate (1%) than the 0.5% that is found for urea in temperate areas [Bouwman, 1994]. Also the NO losses were higher (2%) than the 0.5% of applied N fertilizer emitted as NO in temperate agricultu