Nitrogen Source, Timing, and Placement for Corn.

The recent introduction of new nitrogen (N) fertilizer sources encourages farmers to re-evaluate N management decisions.  The objectives of this multi-year study were to determine the effect of various N sources, application timings, and placements on corn grain yield, N uptake, N use efficiency, and economic return.  The study was conducted on tile drained Nicollet-Webster clay loam soils (Aquic Hapludolls and Typic Endoquolls, respectively).  Treatments included four N sources (ESN, urea, Nitamine and anhydrous ammonia), two placements (band and broadcast-incorporated), two timings (fall vs. spring), and a control (zero N).  All N sources were applied at 112 kg N ha^-1. Treatments were arranged as a partial factorial of a randomized complete block design with four reps.  Corn grain yield, N uptake, and N use efficiency were not different among urea and ESN sources.  Corn yields were greater in two of three years when fall applied ESN was banded versus broadcast-incorporated.  Spring application increased corn grain yields 0.3 Mg ha^-1 compared with fall application, when averaged across ESN, urea, and Nitamine sources.  These data showed no economic advantage for controlled-release N sources compared with conventional sources.