Comparison of Ammonia Volatilization from Surface Applied Fertilizers on High, Neutral, and Low pH 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 a twenty eight-day period on soil pH classes 5.9, 6.96, 8,03; showing volatilization peaked the second or third day for urea and peak times varying for products containing urease inhibitors after application of fertilizer.  Among the fertilizers, urea had the highest amount of NH₃⁺ volatilization over the 28 d study (1197.11 mg m^-2 NH₃⁺) followed by urea/AMS(301.44mg m^-2 NH₃⁺ .  The urea fertilizer combined with urease inhibitors had significantly lower amounts of NH₃⁺ volatilization with highest amount being Eclipse (269.99  mg m^-2 NH₃⁺), followed by Limus (262.99 mg m^-2 NH₃⁺), Agrotain (253.75 mg m^-2 NH₃⁺), and ESN (98.5 mg m^-2 NH₃⁺). The non-urea fertilizer had low amounts of NH₃⁺ volatilization (AMS 134.65 mg m^-2, and FUSN = 40.4 mg m^-2 NH₃⁺; Fig. 3). These results suggest 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/AMS 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 Urea/AMS, and higher N analysis than AMS. As well as indicating that ESN showed a significant decrease  in NH₃⁺ volatilization, , similar to the urease inhibitor products. Although longer observations may be necessary due to indication of increased volatilization at the end of 28 days.

Keywords: Nitrogen, NH₃⁺, volatilization, urease