Nitrogen losses from nine nitrogen fertilizers, applied to four different topsoil samples, were compared in the laboratory. Total N losses were determined 28 days after application, as a difference between the extractable soil nitrogen initially and after 28 days. The ammonia volatilized during this period was determined. By subtracting this ammonia nitrogen loss from the total nitrogen loss, the‘denitrification’loss was estimated. Ammonia volatilization was important from aqua ammonia, urea or UAN for two soil samples with a clay content of 9,5% and 32,3%, and if the soil pH (H2O) increased above 7,0 as a result of fertilizer application.