Nitrogen fertilizer setback and planting density both affect wheat yield. However, the differences in winter wheat yield and its components, canopy structure, and microenvironment caused by N fertilizer setback at different planting densities are not clear. A two-year field experiment was conducted to investigate the most suitable planting density and N fertilizer setback combinations for winter wheat. Three planting densities of 3.3, 2.36, and 1.77 million plants·hm⁻², and two basal fertilizer/nodulation and fertilizer/spike fertilizer ratios of 6:4:0 and 4:3:3, respectively, were used in the experiment. The results of the two-year experiment showed that, under the same planting density, the yields of wheat with nitrogen fertilizer setback increased by 8.2%, 2.7%, and 2.8%, respectively; the total leaf area of the upper trifoliate leaves increased by 10.7–17.4%; and the leaf area index (LAI) increased by 5.4% and 5.3%, respectively. The results showed that the yield, the effective number of spikes, leaf area index, and vertical light interception of wheat at a density of 3.30 million plants·hm⁻² were higher than those of the other treatments. In both years of the experiment, the planting density of 3.30 million plants·hm⁻² with nitrogen fertilizer setback (basal fertilizer/nodulation fertilizer/spike fertilizer = 4:3:3) was the best. Therefore, a nitrogen application of 240 kg·hm⁻² and a planting density of 3.30 million hm⁻² with nitrogen fertilizer setback was found to be the best combination.

Introduction: The research on improving the salt tolerance of crops through plant nanobiotechnology has been extensively reported. However, the mechanism by which plant - derived nanomaterials enhance the germination rate of wheat under salt stress remains elusive. Unveiling the mechanism by which plant - derived nanomaterials boost the salt tolerance of wheat is conducive to safeguarding food security.Methods: Herein, we used mesoporous self-assembly licorice and wolfberry-derived complex nanomaterial (LW-CNs) to soak wheat (Triticum aestivum L) seeds.Results: The size and zeta potential of LW-CNs were 42.2±8.2 nm and ^-19.6±1.5 eV, respectively. After 4 days of salt stress, LW-CNs-soaked wheat seeds presented a higher germination rate (78.4±8.3 vs 54.4±8.5%) and protein content (44.0±0.1 vs 39.1±0.2 mg g^-1), but no significant effect was observed on fresh weight (2.6±0.4 vs 2.3±0.4 g). LW-CNs significantly increased the pigment content (chlorophyll a: 0.11±0.0 vs 0.03±0.0 mg g^-1, chlorophyll b: 0.05±0.0 vs 0.02±0.0 mg g^-1, and carotenoids: 10.3±0.0 vs 2.9±0.0 μg g^-1). LW-CNs alleviated salt-induced reactive oxygen species (ROS) accumulated through increase superoxide dismutase (917.4±8.7 vs 767.5±1.6 U g^-1), peroxidase (2458.7±5.0 vs 2070.5±14.8 U g^-1), and catalase (158.3±3.9 vs 112.0±3.2 μmol min^-1 g^-1) activity. Soaking in LW-CNs maintained ROS homeostasis also through the ascorbic acid–glutathione cycle. Furthermore, LW-CNs elevated the K⁺/Na⁺ ratio within wheat seeds and augmented the activities of nitrogen metabolism enzymes.Conclusion: Overall, our study demonstrates that soaking seeds with plant - derived nanomaterials promotes the growth and nutrient absorption of wheat under salt stress by modulating the homeostasis of reactive oxygen species (ROS) and the K⁺/Na⁺ ratio/.