Agricultural soils often receive annual applications of manure for long periods. Our objective was to quantify the effects of 19 consecutive years of pig (Sus scrofa) slurry (PS) application to a loamy soil (loamy, mixed, frigid Aeric Haplaquept) on N2O emissions. Soil surface N2O fluxes (F(N20)) were measured 36 times in 1 yr. Nitrous oxide concentration profiles, soil NH4(+)- and NO3(-)-N contents, denitrifying enzyme activity (DEA), and denitrification rate (DR) in soil were also determined to explain the variation in F(N20). Long-term (19 yr) treatments on continuous silage maize (Zea mays L.) were 60 (PS60) and 120 Mg ha-1 yr-1 (PS120) of pig slurry and a control receiving mineral fertilizer at a dose of 150 kg ha-1 each of N, P2O5, and K2O. Denitrifying enzyme activity, soil N2O concentrations, and F(N20) (<25 ng m-2 s-1) were low in the control plots receiving mineral fertilizer. Annual applications of PS to the soil for 18 yr had positive residual effects on the DEA compared with the long-term fertilized control plots. Following PS application, there was a strong and rapid increase of F(N20) (up to 350 ng m-2 s-1) on manured plots. The PS-induced F(N20) increased with increasing quantity of PS, probably as the result of a greater availability of NO3(-)-N for denitrification. The effects of PS on F(N20) were mostly limited to the 30 d following application, with low fluxes (<10 ng m-2 s-1) during the rest of the measurement period. Total N2O-N emissions represented 0.62, 1.23, and 1.65% of total N applied in control, PS60, and PS120 plots, respectively. These emission factors for the PS plots agreed with values previously suggested for N-fertilized soils (1.25%).