Evaluation of Nitrogen-Loss Prevention Products in North Carolina.

Determining optimum N fertilization rates is critical to preventing over-application and environmental losses of N to air and water, thus field trials were designed to: 1) determine optimum N rates for corn and wheat in three different regions of North Carolina (Coastal Plain, Piedmont, and Mountains); and 2) determine the value of alternative fertilizer additives in reducing N losses. The standard fertilizer treatment UAN was compared to UAN with AgrotainPlus®, UAN with Instinct®, and UAN with NZone® at six different N rates in corn and five different N rates in wheat. A linear-plateau statistical model determined the optimum N rates for the 2014 crop as 150, 117, and 66 kg ha^-1 for corn in the Coastal Plain, Piedmont, and the Mountains, respectively. There was a N rate response at all locations, but no yield advantage from fertilizer additives. These values, Mountains excluded, align closely with current recommendations in the North Carolina Realistic Yield Expectation database. Wheat spring N applications (2014) were optimum at 124 kg ha^-1 in the Coastal Plain and 112 kg ha^-1 at the Piedmont location. At the Coastal Plain location, the yield of UAN with Instinct was statistically significant compared to UAN (5717 vs. 5448 kg ha^-1, respectively). The fertilizer additives were not statistically significant for wheat yield at the Piedmont location. Preliminary results indicate that these products may not significantly prevent N loss compared to UAN alone, indicating that proper N application rates may be a more efficient nutrient management strategy. A separate experiment compared six differently timed applications of Environmentally Smart Nitrogen (ESN®), with and without ammonium sulfate (AS) to UAN on wheat. In the Coastal Plain, the recommended split-N application of AS and UAN showed yields significantly higher than various rates of ESN. In the Piedmont, results were not significant by fertilizer source or timing.