Comparison of Ammonia Volatilization for Urea-Based Fertilizers in Acidic, Neutral, and Basic Soils.

Urea and ammonium based fertilizer are susceptible to rapid loss via ammonia (NH₃⁺) volatilization immediately following fertilizer application, but NH₃⁺ volatilization losses can be reduced if the fertilizers are incorporated. In pasture and no-till operations, fertilizer incorporation may not be possible leaving the fertilizer susceptible to rapid ammonia volatilization from the soil surface. New N fertilizer products and urease and nitrification inhibitors have been developed that may reduce the rate of NH₃⁺ volatilization. The objective of this study was to compare NH₃⁺ volatilization among these products which includes an ammonium sulfate-nitrate fused fertilizer FUSN, urea and ammonium based fertilizers that utilize this technology. Ammonia volatilization was measured over an eight-day period on soil pH classes 5.9, 7.0, 7.8; showing volatilization peaked the second or third day after application of fertilizer.  Among the fertilizers, urea had the highest amount of NH₃⁺ volatilization over the 8 d study (1229.78  mg m^-2 NH₃⁺) followed by urea N-N(1148.1 mg m^-2 NH₃⁺), Amidas(1005 mg m^-2 NH₃⁺) urea/AMS(395.6 mg m^-2 NH₃⁺), UAN N-N(476.7 mg m^-2 NH₃⁺), and UAN(439.7 mg m^-2 NH₃⁺).  The urea fertilizer combined with urease inhibitors had significantly lower amounts of NH₃⁺ volatilization with highest amount being Eclipse (195.6 mg m^-2 NH₃⁺), followed by Agrotain (133.68 mg m^-2 NH₃⁺), ESN(111.9 mg m^-2 NH₃⁺), and Limus(98.5 mg m^-2 NH₃⁺). The non-urea fertilizer had low amounts of NH₃⁺ volatilization (AMS = 53.78 mg m^-2, and FUSN = 40.4 mg m^-2 NH₃⁺; Fig. 3). These results suggest Nutrisphere-N may be inhibiting urease, but not preventing the conversion of NH₄⁺ to NH₃⁺.  Also suggesting that the urease inhibitors are a reliable product to reduce to NH₃⁺volatilization. Regarding the ammonia volatilization among the three soil pH classes by fertilizer the results differ per class. All soil classes presented had concurring results for highest total NH₃⁺, with urea followed by urea N-N for the highest. This research indicates FUSN is potentially a good source for crop production, because it had significantly lower NH₃ volatilization than Urea and UAN, and higher N analysis than AMS.