Nitrogen Effects on Grain Yield and Yield Components of Leafy and Nonleafy Maize Genotypes

Effects of N fertilization have been extensively studied for conventional maize (Zea mays L.) hybrids but not for genotypes bearing the leafy and reduced‐stature traits which differ significantly in canopy and root morphology. We tested the hypothesis that genotypes carrying the leafy trait (taller plants with more leaves, greater leaf area development, and greater rooting systems) would show differing responses to N availability in terms of grain yield and yield components from those of conventional maize hybrids. The experimental design was a split‐plot in a randomized complete block design with four blocks repeated across two growing seasons at each of two field sites. The treatments were N fertilization rates (0, 85, 170, and 255 kg N ha−1) as the main plot factors and genotypes as the subplot factors. The genotypes were leafy reduced stature (LRS), nonleafy normal stature (NLNS), leafy normal stature (LNS), nonleafy reduced stature (NLRS), and conventional hybrid checks of early (P3979) and late maturity (P3905). The latter consistently yielded best and the NLRS hybrid worst; however, the genotypic grain yield ranking varied between sites. Overall, the LRS outyielded its conventional counterpart (P3979) by 12% at one site and by 26% at the other. No significant N × hybrid interactions were detected for grain yield. We inferred that using leafy genotypes in maize production would not require additional N fertilization compared with their conventional maize hybrid counterparts.