The article presents the research (2020-2021) on the effect of ammonium sulphate on the yield structure and yield of spring mustard of the variety Yunona on the leached chernozem of the Western Ciscaucasia. We established that the highest effectiveness of ammonium sulphate application on brown mustard sowings was achieved by split application of N22S25 at the seedling stage and N22S25 at the stem extension stage. These methods help increase the yield by 0.05-0.44 t/ha in comparison with the control due to an increase in thousand-seed weight by 18-48 %, the number of productive branches on one plant by 11-22 %, pods – by 5.5-28 %, and seeds in a pod – by 11-18 %.