Objective This study aims to investigate the effects of water and nitrogen regulation on the emission patterns of NH₃ and N₂O and the nitrogen fertilizer utilization rate in saline-alkali farmland. Methods Sunflower was used as the research subject. Two irrigation gradients were set： T1， mild deficit irrigation （field capacity 65%-75%）， and T2， full irrigation （field capacity 75%-80%）. Four nitrogen application levels were established： N1 （0 kg/hm²）， N2 （150 kg/hm²）， N3 （225 kg/hm²）， and N4 （300 kg/hm²）. By analyzing the effects of different irrigation gradients and nitrogen application levels on NH₃ and N₂O emissions， the pattern characteristics of nitrogen fertilizer utilization， residue， and loss in saline-alkali land were clarified. Results Under the two irrigation conditions， with increasing nitrogen application rate， both the N₂O emission flux and NH₃ volatilization rate significantly increased. Peak emissions under the N4 treatment were 4.4%-21.4% higher than those under N3 and N2. Under the same nitrogen application level， the cumulative NH₃ volatilization and N₂O emissions under the T2 treatment were 10.10%-20.41% and 16.41%-39.77% higher than those under the T1 treatment， respectively. The gaseous nitrogen fertilizer loss rate under the T1 treatment was 7.05%-32.38% lower than that under the T2 treatment. The ¹⁵N isotope tracing results showed that the fate of fertilizer nitrogen followed the pattern： nitrogen fertilizer loss rate > nitrogen fertilizer residual rate > nitrogen fertilizer utilization rate. The residual fertilizer nitrogen was mainly concentrated in the 0-20 cm soil layer， accounting for 46.13%-63.14% of the total residual amount， and gradually decreased with increasing soil layer depth. Under the T1 treatment， the sunflower yield was higher than that under the T2 treatment by 4.12%-12.38%. The nitrogen fertilizer utilization rate under the T1 treatment was 8.46%-14.96% higher than that under the T2 treatment. Among them， the T1-N3 treatment achieved the highest yield and nitrogen fertilizer utilization rate， reaching 2 796.01 kg/hm² and 26.10%， respectively. Additionally， the effects of salinity on the nitrogen transformation process were mainly related to the composition of salt ions， and Na⁺+K⁺ and \mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-} were positively correlated with the gaseous nitrogen emission rate （r = 0.57-0.86）. Conclusion For severely saline-alkali farmland， under mild deficit irrigation conditions， a nitrogen application level of 225 kg/hm² （T1N3） can effectively reduce nitrogen fertilizer residue and gaseous losses while ensuring nitrogen fertilizer utilization efficiency， representing the optimal water and nitrogen management mode for emission reduction and efficiency improvement.