Both genetic improvement and the application of N fertilizer increase the quality and yields of wheat. However, the molecular kinetics that underlies the differences between them are not well understood. In this study, we performed a non-targeted metabolomic analysis on wheat cultivars from different release years to comprehensively investigate the metabolic differences between cultivar and N treatments. The results revealed that the plant height and tiller number steadily decreased with increased ears numbers, whereas the grain number and weight increased with genetic improvement. Following the addition of N fertilizer, the panicle numbers and grain weights increased in an old cultivar, whereas the panicle number and grain number per panicle increased in a modern cultivar. For the 1950s to 2010s cultivar, the yield increases due to genetic improvements ranged from −1.9% to 96.7%, whereas that of N application ranged from 19.1% to 81.6%. Based on the untargeted metabolomics approach, the findings demonstrated that genetic improvements induced 1.4 to 7.4 times more metabolic alterations than N fertilizer supply. After the addition of N, 69.6%, 29.4%, and 33.3% of the differential metabolites were upregulated in the 1950s, 1980s, and 2010s cultivars, respectively. The results of metabolic pathway analysis of the identified differential metabolites via genetic improvement indicated enrichment in 1-2 KEGG pathways, whereas the application of N fertilizer enriched 2–4 pathways. Our results provide new insights into the molecular mechanisms of wheat quality and grain yield developments.

Investigating the interaction effect of nitrogen (N) management strategies and stay-green types of maize hybrids is essential for enhancing N use efficiency and developing N-efficient hybrids. A field experiment was conducted with five N management treatments (Control, Opt.N*70%, Opt.N, Opt.N*130%, and Con.N) and two stay-green types of maize hybrids (stay-green hybrids: DH605 and ZD958; moderate-green hybrids: XY335 and XY1266) to examine their interaction effects on maize yield, aboveground biomass, and N uptake and allocation. The highest grain yields for moderate stay-green and over stay-green maize hybrids were 12.8 Mg ha⁻¹ and 10.8 Mg ha⁻¹, respectively. Compared to over stay-green hybrids, moderate stay-green hybrids exhibited a significantly higher aboveground biomass and N uptake. Under an optimal N (Opt.N) treatment, moderate stay-green hybrids achieved a 15.8% higher grain yield than over stay-green hybrids. Under the Opt.N*130% treatment, moderate stay-green hybrids had the highest grain N concentration, averaging 13.1 g kg⁻¹. Nitrogen application enhanced N allocation to grains, resulting in a 3.1–7.7% increase in grain N content. Moderate stay-green hybrids with optimal N management exhibited a 1.9% higher grain N content compared to over stay-green hybrids, whereas their vegetative organs had a relatively lower N content except for the Opt.N*130% treatment. Selecting a suitable maize hybrid (e.g., moderate stay-green maturity hybrid, XY335) and optimizing N fertilizer management can enhance grain yield, grain N content, and enhance N absorption and utilization efficiency.