Soil salinity typically exhibits non-uniform distribution in the natural environment. However, how vertically non-uniform distribution of soil salinity in the root zone (VNDSR) regulated plant nitrogen metabolism is still largely elusive. This study aimed to investigate the impact of VNDSR on leaf Malondialdehyde (MDA) content, upper and lower root activity, leaf Na+/Ca2+ and Na+/K+, various tomato organs' nitrogen concentration (%) and natural abundance of nitrogen isotopes (delta N-15,parts per thousand), and nitrogen utilization efficiency of tomato plants. Four treatments were established, including the upper layer of the root zone having soil salinity levels of 1 parts per thousand, 1 parts per thousand, 2 parts per thousand, and 3 parts per thousand, while the corresponding lower layer of the root zone had soil salinity levels of 1 parts per thousand, 5 parts per thousand, 4 parts per thousand, and 3 parts per thousand, respectively, denoted as T-1:1, T-1:5, T-2:4, and T-3:3. The results showed that under the same average soil salinity conditions and compared to the treatment with uniform soil salinity distribution in the root zone (T-3:3), the VNDSR treatment (T-1:5) significantly reduced leaf MDA content (p < 0.01), Na+/Ca2+ (p < 0.01) and Na+/K+ (p < 0.01), and stem delta N-15 values (p < 0.05). Moreover, the VNDSR treatment (T-1:5) significantly increased the ratio of upper and lower root biomass-weighted root activity (p < 0.01), tomato fruit yield (p < 0.01), and nitrogen partial factor productivity (PFP, gg(-1), p < 0.01) compared to uniform salt distribution treatment (T-3:3). There were significant positive correlations (p < 0.05) between leaf delta N-15 values and Nitrogen Absorption Ratio (NAR, %, p < 0.05) and PFP (p < 0.05), indicating that under VNDSR, delta N-15 values can serve as an indicator that comprehensively reflects the information of plant nitrogen utilization efficiency. In conclusion, the VNDSR could mitigate the damage of salt stress to tomatoes, enhance plant nitrogen uptake and utilization efficiency, and promote the growth and development of tomatoes.

来源平台：ENVIRONMENTAL AND EXPERIMENTAL BOTANY