Effect of Nitrogen Efficiency Enhancers On Corn Growth and Yield at Multiple N-Rates.

Corn requires large quantities of water and N to achieve high yields.  Efficiency enhancers (EE) may reduce N losses, especially in the sandy soils of the Coastal Plains.  The objective of this study was to determine if EE added to Urea Ammonium Nitrate (UAN, 32-0-0) would result in improved plant size or yield than UAN alone.  A strip-plot design was used to evaluate side-dress applications of UAN treated with EEs – Agrotain Plus (AP) or Nutrisphere-N (NN) compared to UAN alone at 13 rates (0 to 168 kg N ha^-1) in Attapulgus, GA and 14 rates (0 to 196 kg N ha^-1) in Tifton, GA.  There were no statistical differences in any measured variable (yield, weight per ear, or whole plant biomass at mid-season) among UAN, UAN+AP, and UAN+NN.  There were differences among N rates.  At Attapulgus, very dry conditions coupled with irrigation problems caused yields to be very low, but treatment trends were similar to Tifton.  There were no statistical differences in grain yield for rates above 126 kg N ha^-1 (3.3 to 4.0 Mg ha^-1) at Attapulgus, and there were no differences in yield for rates above 72 kg N ha^-1 (7.0 to 8.5 Mg ha^-1) in Tifton.  Weight per ear resulted in no differences for rates above 100 kg N ha^-1 (45 to 57 g) at Attapulgus, and no differences for rates above 72 kg N ha^-1 (85 to 103 g) in Tifton.  Mid-season whole plant biomass was taken only at Attapulgus, with no differences for rates above 85 kg N ha^-1 (107 to 126 g plant^-1).  Based on these results, addition of EE for N do not result in improved plant performance and rate plays a more important role in achieving yield goals.