Fertilized agricultural soils and soils cropped with legumes can be a significant source of atmospheric N₂O. By modifying soil physical, chemical and biological properties, tillage may considerably influence N₂O emissions from soils. In this study, we measured N₂O fluxes from corn and soybean long-term plots (13 yrs) that were managed with either no-till (NT) or moldboard plowing (MP) and with various rates of mineral N fertilizer. Fluxes were measured in corn (Zea mays) receiving 0, 80 and 160 kg N ha^-1 as NH₄NO₃ in 2004, and on unfertilized soybean (Glycine max) in 2005.  In 2004, the cumulative N₂O-N lost from soil increased linearly with the amount of mineral nitrogen (N) fertilizer applied (1.0, 2.0 et 2.5 kg N ha^-1 in the plots receiving 0, 80 and 160 kg N ha^-1, respectively).  The fertilizer-induced N₂O emissions during the corn year agreed with the 2006 IPCC default value (0.01 kg N₂O-N/kg N).  The cumulative N₂O-N lost from soil did not vary with tillage. In 2005 under soybean, cumulative N₂O-N emissions were higher under NT (2.52 kg N ha^-1) than under MP (1.52 kg N ha^-1), and were not different among rates of N fertilizer applied in 2004. At different sampling periods, N₂O concentration in soil and fluxes were correlated to soil NO₃-N, water filled pore space and rainfall. Rainfall was 50% greater in 2005 than in 2004.  It is hypothesized that the increased N₂O emissions under no-till in 2005 were the result of higher denitrification rates in the denser no-till soil under wetter soil conditions.