Response of a Leafy and Non-Leafy Maize Hybrid to Population Densities and Fertilizer Nitrogen Levels

Optimum plant population density (PPD) of maize (Zea mays L.) for grain and/or silage production depends on hybrid type, soil fertility and agronomic management. Limited information exists on the yield response of Leafy maize hybrids to different PPD under varying N application rates. A field study was conducted during 2003 and 2004 in Ottawa, Canada to evaluate grain and silage yields of a Leafy hybrid (‘Maizex LF850 RR’) with a conventional hybrid (‘Pioneer 3893’), under three PPD (60 000, 75 000, and 90 000 plants ha⁻¹) and four N fertilizer (0, 75, 150, and 225 kg N ha⁻¹) regimes. Canopy light interception, plant dry matter (DM), silage, and grain yield were measured. The Leafy hybrid had 20 to 25% more leaf area, on an individual plant basis, and produced significantly greater silage DM (21.1 vs. 20.0 Mg ha⁻¹), but had a significantly smaller grain yield (9.4 Mg ha⁻¹) than the conventional hybrid (9.7 Mg ha⁻¹). The Leafy hybrid was more sensitive to high density and low N stresses, resulting in more barren plants (up to 15%), lower harvest index (HI), thus significantly lower grain yield than the conventional hybrid in 2003. Grain yield reached to a maximum with 225 kg N ha⁻¹ followed by 75 and 150 kg N ha⁻¹, but silage DM was not different between 150 and 225 kg N ha⁻¹ Plant population density had no effect on grain yield but silage yield increased linearly as PPD increased from 60 000 to 90 000 plants ha⁻¹ Within the tested range of PPD, no differential response of hybrids was observed in terms of grain yield or silage DM, and N treatments had no effect on response of hybrids to PPD. We conclude that the Leafy hybrid was more sensitive to high PPD and low N stresses than the conventional hybrid especially for grain production. The optimum PPD for silage production may be beyond 90 000 plants ha⁻¹ for both types of hybrids.