Layered nitrogen (N) application to wheat is intended to avert nutrient retention in the topsoil, which limits deep root development and grain yield. In a two-year field experiment on the Loess Plateau comparing two N treatments: 240 kg N ha⁻¹ applied at the 8-cm soil depth or in a 1:2:1 ratio to the 8-, 16-, and 24-cm soil layers, the layered treatment increased grain yield, post-anthesis N accumulation, phosphorus (P) accumulation, root biomass, and soil organic carbon and available P in the 8−24 cm layers. It also upregulated N and P transporter genes in roots across different soil layers. Layered N application optimized the vertical nutrient distribution in the wheat root zone, induced adaptive root architectural development, and activated the transcriptional regulatory network of nutrient uptake, which peomoted post-anthesis nutrient assimilation and ultimately improving grain yield.

Winter wheat is a key staple crop in Northwest China, yet optimizing its productivity and economic returns remains a challenge due to water constraints and suboptimal planting densities. This study evaluates the combined effects of irrigation strategies and planting density (PD) on winter wheat yield, resource-use efficiency, and net economic benefits (NEB). A two-year field experiment was conducted under four irrigation treatments (I1, no irrigation; I2, before winter and jointing; I3, jointing; I4, jointing and anthesis) and three PD treatments (PD1, 562.5×10⁴ plants ha^–1; PD2, 375 ×10⁴ plants ha^–1; PD3, 187.5×10⁴ plants ha^–1). Through field trials, we identified optimal water-saving irrigation regimes and planting densities that maximize grain yield while enhancing water productivity. Our results demonstrated that lower PD (187.5×10⁴ plants ha^–1) under reduced irrigation significantly improved dry matter accumulation (DMA), SPAD, and leaf area index (LAI), leading to higher grain yield. Moderate irrigation at the jointing stage (I3) enhanced grain yield in higher planting densities by up to 18.42% compared to other irrigation regimes, while the highest overall yield (6,310 kg ha^–1) was achieved in medium PD under the I3 irrigation. Water-use efficiency (WUE) was significantly improved by reducing irrigation at specific growth stages, mitigating excessive evapotranspiration. PD3–I3 achieved the highest NEB, exceeding I1, I2, and I4 by 11.9, 18.4, and 16.4%, respectively, in 2022–2023 and by 15.1, 14.0, and 8.4%, respectively, in 2023–2024. The findings provide practical insights for sustainable wheat production, ensuring higher profitability while conserving water resources. Implementing optimized irrigation and PD strategies offers a strategic pathway to improving food security and farm income in the semi-arid regions of Northwest China.

Nitrogen is a key nutrient for wheat (Triticum aestivum L.) growth and yield, particularly during the grain-filling stage, where most nitrogen is redistributed from vegetative organs to the grain, significantly influencing yield. However, it remains unclear during which period the nitrogen translocation from the vegetative phase to grain maturation occurs and how it correlates with flag leaf senescence. In this study, a field experiment was conducted using the winter wheat cultivar ‘Xinong 511’ under two nitrogen fertilizer treatments: regular nitrogen supply (240 kg ha^–1 (N₂₄₀)) and no nitrogen supply (0 kg ha^–1 (N₀)). The results revealed that nitrogen accumulation in wheat flag leaves peaked at 7–14 days, with a nitrogen content 4.55%, after which nitrogen was redistributed to the grains. Nitrogen content in flag leaves decreased by 56% during 21–35 days, while that in the grains increased by 51%. The plant analysis development value (relative chlorophyll content), photosynthetic rate, free amino acid concentration, and soluble protein content in flag leaves peaked at 7–14 days, indicating nitrogen transportation from the flag leaves to the grains. Nitrogen application significantly increased the nitrogen remobilization rate in flag leaves by 20% compared with that of N₀, reduced reactive oxygen species accumulation by 21%, and delayed flag leaf senescence. Under nitrogen deficiency, autophagy was induced earlier, with a 5–7-fold increase in the expression of autophagy-related genes (TaATG8), suggesting that regulation of the autophagy pathway and enhancement of autophagy activity can optimize nitrogen fertilization. Our study demonstrates that the remobilization of nitrogen from vegetative parts to grains initiates leaf senescence and is closely correlated with the expression of autophagy-related genes.