NITROGEN UPTAKE AND UTILIZATION EFFICIENCY OF MAIZE HYBRIDS UNDER HIGH AND LIMITED NUTRIENT SUPPLY

Maize (Zea maysL.) genotypes with improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha-1) and low-N (100 kg N ha-1) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1in the low-yielding (dry) environment to 55 kg grain kg N-1under higher yielding environment. When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.