Layered nitrogen application increases post-anthesis nutrient accumulation and grain yield of wheat by coordinating root morphology and nutrient transporter gene expression

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.