Context. An appropriate use of the fertiliser technology may lead to a more efficient N absorption and to the reduction of economic and environmental costs. Aims. This study sought to quantify N2O emissions generated from soil and the residual nitrate (NO3-) up to 2 m depth in field conditions in a maize crop under supplementary irrigation and fertilised with two nitrogen (N) sources (UAN and urea) at increasing N rates (0, 80, 160 and 250 kg N ha(-1)) in the Semi-arid Argentine Pampas. Methods. Throughout the crop cycle, emissions were monitored daily with static chambers during the first week after fertilisation; then sampling frequency was gradually reduced until the end of the experiment. Key results. There were no yield responses to the use of different sources and N rates. Crop N uptake saturated at 80 kg N ha(-1), reaching 300-310 kg N ha(-1). Residual NO3- increased significantly with the highest rates of N fertiliser. Total N2O emissions differed significantly only among fertiliser rates. The N2O emissions were lower at 80 than at 160 and 250 kg N ha(-1). Conclusions. The N2O emissions measured were lower than those calculated by the IPCC, even when only direct emissions were considered. No grain yield increase was observed due to N fertilisation, with a non-limiting supply of N-NO3- at the beginning of the crop cycle and of N from mineralisation. Implications. This excess of N can generate negative environmental effects due to higher emissions of N2O and residual N-NO3- that can be leached.