Lack of Hybrid by Seeding Rate Interactions for Corn Growth, Silage Yield, and Quality

Transgenic Bt (Bacillus thuringiensis) corn (Zea mays L.) hybrids may require higher but brown midrib (BMR) and leafy hybrids may require lower seeding rates than currently recommended for silage in the northeastern United States. We planted dual-purpose (three Bt and one non-Bt) two silage-specific and two BMR hybrids to evaluate growth, dry matter (DM) yield, and quality responses to four seeding rates (61,750–98,800 kernels ha−1). Hybrid × seeding rate interactions were not observed. At silking (R1), BMR hybrids averaged 6% lower leaf area index (LAI, 4.58) compared with dual-purpose hybrids and 7% lower biomass (1050 g m−2) compared with two dual-purpose hybrids. Crop growth rates were similar from the 14th leaf (V14) to R1 stage between BMR and dual-purpose hybrids (34.3–35.8 g m−2 d−1) so less BMR vegetative growth was associated with 10% lower LAI (3.46) and biomass (480 g m−2) at V14. Biomass and LAI had linear responses to seeding rates. The BMR compared with two dual-purpose hybrids averaged 8% lower DM yield (20.7 Mg ha−1) but similar predicted milk yield (37.6 Mg ha−1) because of 8% higher milk Mg−1 values (1823 kg Mg−1). Silage-specific compared with two dual-purpose hybrids averaged about 7.5% lower DM and milk yields because of similar milk Mg−1 (1685 kg Mg−1). Milk and DM yields showed quadratic, and milk Mg−1 showed negative linear responses to seeding rates. Results indicate that Bt, BMR, and silage-specific hybrids should be seeded at about 89,000 kernels ha−1 for silage in New York.