Fertilization of Corn Including N-Efficiency Enhancers in Georgia.

Nitrogen efficiency enhancer (NEE) products are designed to increase N-use efficiency and reduce non-target losses through reduced volatilization and nitrification, plus urease inhibition.  However, these fertilizer additives are an added expense and need to be proven in many different soil types and growing conditions for numerous crops before they are readily accepted.  The objective of this trial was to evaluate corn response to various rates of N fertilization with and without N-enhancer products.  Experiments took place from 2009-2011 on a Tifton loamy sand and a Suches loam in southern (Tifton) and northern (Blairsville) GA, respectively.  In one set of experiments, urea ammonium nitrate (UAN, 32-0-0) was used alone or in combination with N-(n-butyl) thiophosphoric tramide (NBPT) + dicyandiamide (DCD) or with maleic-itaconic copolymer calcium salt (MIC) with each treatment applied at 34 kg ha^-1 increments from 0 to 269 kg ha^-1 as a one-time sidedress application at V6.  Another set of experiments compared the same fertilizer treatments above, but as a sidedress rate of 56 kg ha^-1 increments from 0 to 224 kg ha^-1 at V6 following an at-plant application of 58 kg N ha^-1 and 45 kg P₂O₅ ha^-1, versus one completely unfertilized check.  Corn responded to N rates, but there were no indications that the NEE additives provided a yield increase in any trial or location.  The objectives of these trials were not to evaluate whether the products met the claims of reduced volatilization, nitrification, etc. but merely whether they would be effective in typical Georgia growing conditions.  Based on these results, the supplementation of UAN with NEE products is not worthwhile or cost-effective over a large range of N-rates, and maximized production was in the range of 168 – 202 kg N ha^-1.