Soil salinization poses a serious threat to global food security, as high Na⁺ contents in soils hinder nitrogen use efficiency (NUE), affecting the growth and yield of crop plants. The present study aims to explore the effects of different nitrogen fertilizer types viz., NO₃⁻ (N1) and NH₄⁺ (N2) and planting densities, viz., D1: 30 × 10 cm, D2: 20 × 20 cm, and D3: 30 × 20 cm, on growth and development, nitrogen absorption and utilization, and yield formation. The salt-tolerant rice variety ‘Jingliangyou 3261’ was exposed to 0.3% salt irrigation water. Results revealed that N2 substantially improved the rice yield by increasing the number of effective panicles and the rate of grain-setting compared to N1. In addition, the N2 also increased leaf chlorophyll content, dry matter accumulation, antioxidant enzyme activity such as superoxide dismutase, peroxidase, and catalase activity and reduced the content of malondialdehyde. In comparison with N1, the N2 treatment resulted in an increase of 12.21%, 31.89%, and 37.53% in total nitrogen accumulation, nitrogen recovery efficiency (NRE), and nitrogen agronomic efficiency (NAE), respectively. This increase can be attributed to enhanced leaf nitrogen metabolic enzyme activity, including nitrate reductase and glutamine synthetase, and a more robust root system. Under N1 and N2 conditions, compared to D3, D1 resulted in an increase in the number of tillers but decreased the percentage of productive tillers, the grains per panicle, the grain-filling rate, and the thousand-grain weight, thereby reducing yield. Additionally, the D3 treatment also significantly improved NRE and NAE compared to the D1 treatment. Therefore, the rational selection of nitrogen fertilizer type (N2) and planting density (D3) is crucial for improving the yield and nitrogen use efficiency of salt-tolerant rice. This would broaden the scope of agricultural solutions for saline soils, potentially improving food security in regions where soil salinization is a widespread issue.

The present study aimed to investigate the effects of different soil amendments coupled with nitrogen fertilizer on the morpho-physiological characteristics and yield of salt-tolerant rice under saline conditions. The soil amendments, i.e., S1: zeolite amendment, S2: coconut coir amendment, S3: humic acid amendment, and S0: no amendment, and fertilizer treatments, i.e., N1: urea, N2: slow-release urea, and N0: no N fertilizer, were kept in main plots and sub-plots, respectively, in a split-plot design. The salt-tolerant variety ‘Shuangliangyou 138’ was exposed to 0.3% salt irrigation water. The results showed that during the entire growth period, compared to S0, the S1 and S3 treatments increased the SPAD values by an average of 6.3%and 5.5%, respectively, the leaf area index by an average of 24.5% and 19.8%, the canopy interception rate by an average of 11.5% and 4.1%, and the aboveground biomass by an average of 36.8% and 13.9%, respectively. Moreover, under S1 and S3 conditions, the tiller number per square meter, leaf water potential, leaf water content, and chlorophyll contents were also improved under the slow-release urea than urea. Moreover, slow-release urea promoted root vitality and nutrient absorption as well as enhanced the activity of antioxidant and nitrogen metabolism enzymes than urea under the S1 and S3 conditions. In sum, the rational application of soil amendments and slow-release urea could improve the rice productivity on saline-alkali land.