From past to future: Trends in maize N dilution curve

Abstract Background and Aims Maize ( Zea mays L.) grain yield has increased over recent decades due to genetic improvement and advances in crop management, accompanied by greater nitrogen (N) fertilizer use. The N dilution curve provides a physiological framework to diagnose crop N status by describing allometric relationship between aboveground biomass and plant N concentration. However, it remains unclear whether long-term breeding progress and recent architectural have altered this relationship. This study aimed to (i) evaluate historical changes in the maize N dilution curve and (ii) compare N dilution patterns between short- and tall-stature hybrids. Methods Three published datasets including hybrids released between 1930 and 2020 were synthesized and combined with two experiments conducted in the United States and Argentina under non-limiting N conditions. Nitrogen dilution curves were fitted using Bayesian modeling, whole-plant and organ-level (leaf and stem) N dilution dynamics were evaluated. Results The N dilution curve differed between the oldest hybrids (1930–1949) and modern hybrids (1990–2020). Posterior model parameters median across eras were 2.69 for a and 0.22 for b, with no shifts detected among hybrids released from 1950 to 2020. Across field experiments, short- and tall-stature hybrids exhibited similar N dilution patterns at the whole-plant, leaf, and stem levels. Conclusion These findings demonstrate that neither long-term genetic improvement nor reduced plant height alters the core physiological relationships governing N dilution in maize. Overall, the results reinforce the robustness of the N dilution framework and support its use as a physiological reference for understanding crop N status.