Nitrogen Uptake and Response to Radiation Distribution in the Canopy of High-Yield Maize

Nitrogen is an essential element for maize (Zea mays L.). Farmers in developed countries most often apply more N fertilizer than necessary, which reduces N use efficiency (NUE). Improving radiation and N distribution, and thus the NUE of modern maize production systems with high plant density, is of great significance. In this study, field experiments were conducted in 2014 and 2015 in Xinjiang, China, using hybrid maize cultivar DH618 with high density. In addition, a synthesis analysis was conducted using data from 95 publications to observe N characteristics under different yield levels and compare the experimental results with existing studies. The relationship between radiation and N distribution in the canopy of high-yield maize was also assessed. Nitrogen uptake was significantly correlated with grain yield. However, N uptake per unit grain yield and grain N concentration at maturity decreased as grain yield increased. The positive correlations between radiation and leaf and stalk N concentrations at silking showed that N concentration at silking increased as the height of the canopy layer increased because of increased radiation in the canopy. These results indicate that maize hybrids with erect upper leaves and high post-silking N uptake can coordinate and optimize the distribution of radiation and N in different canopy layers and thus improve NUE and yield under high-density production.