Plant Density and Hybrid Impacts on Corn Grain and Forage Yield and Nutrient Uptake

Corn (Zea mays L.) production recommendations should be periodically evaluated to ensure that production practices remain in step with genetic improvements. Since most of the recent increases in corn grain yield are due to planting at higher densities and not to increased per-plant yield, this study was undertaken to measure the effects of plant density and hybrid on corn forage and grain yield and on nutrient uptake. Plant density (4.9, 6.2, 7.4, and 8.6 seeds m-2) and hybrid relative maturity (RM) [early (108 day RM); medium (114 day RM); and late (118 day RM)] combinations were evaluated over five site-years under irrigated and non-irrigated conditions. The interaction of hybrid with plant density was never significant for grain, stem, or leaf biomass. The latest RM hybrid out-yielded the medium and early hybrids by 550 and 1864 kg ha-1, respectively. Grain yield was highest at 8.6 plants m-2. Total stem yield was also greatest at the highest plant density but by only 340 kg ha-1 more than at 7.4 seeds m-2. Based on grain yield response over sites, the estimated optimum density was 7.6 seeds m-2, which is 0.7 seeds m-2 higher than the current recommendation at this average yield level (11.5 Mg ha-1). Grain nitrogen (N), phosphorus (P), and potassium (K) uptakes were highest for the medium RM hybrid. Nutrient uptake levels varied by planting density, with the lowest levels observed at the lowest and highest plant densities. At 4.9 seeds m-2, the reduced uptake is explained by lower biomass yields. At the 8.6 seeds m-2 rate, N and K levels may have been lower due to dilution.