Grain corn and soil nitrogen responses to sidedress nitrogen sources and applications

The efficiency of synthetic N fertilization can be improved by selecting the fertilizer source and application that best matches the soil N supply and crop demand. A field experiment was conducted for 3 yr (2004-2006) on a clay soil near Québec City, QC, Canada, to evaluate the effects of N fertilizer source and application on corn (Zea mays L.) yield, plant N accumulation, and residual soil inorganic N. Treatments consisted of an unfertilized control (0 N) and three sources of N fertilizer (urea ammonium nitrate 32% [UAN], calcium ammonium nitrate [CAN], and aqua ammonia [AA]) applied at three different concentrations (100, 150, and 200 kg N ha-1). Nitrogen fertilizers were banded 5 cm below the soil surface between corn rows at the six-leaf stage every year. Fertilizer source affected grain corn with the highest mean yields (8.9 Mg ha-1) and total plant N accumulation achieved with UAN at any application. For all fertilizer sources, the linear-plus-plateau model best described the corn response to N application with optimum rate at 100, 124, and 128 kg N ha-1 for UAN, CAN, and AA, respectively. At harvest each year, the concentration of residual soil inorganic N increased in the upper layer. Under the cool and humid climatic prevailing conditions, UAN was the most efficient synthetic N fertilizer when banded into the soil at sidedress. © 2010 by the American Society of Agronomy.