Following the development of hybrid maize (Zea mays L.) breeding technologies and advanced agricultural strategies, we postulated that maize grain yield and nitrogen (N) uptake and utilization could be further improved by selecting appropriate hybrids and identifying optimum planting densities. Five field experiments were conducted in 2013, 2014 and 2015 in Jilin Province, China. Our orthogonal design demonstrated significant interactive effects of maize hybrid and planting density on grain yield. The optimum planting densities, i.e., those associated with the best grain yields for hybrids ZD958, XY335 and LM33, were 74.0-81.4, 74.3-79.1, and 78.6-89.7 × 103 ha–1 , respectively, across 3 years and two sites. Increased planting density had a significant inhibitory effect on the leaf growth and development of individual plants, but this was offset by positive effects at the population level: increased planting density significantly increased the population leaf area index. Increased planting density improved dry mass and total aboveground N uptake (TNU), and promoted dry mass and N remobilization in stalks and leaves.
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