Effect of Nitrogen Sources On the Volatilization of Ammonia (NH3-N) On Corn in No-Tillage.

The nitrogen sources have different potential for volatilization of ammonia (NH₃-N), which affects its efficiency, especially superficially on the "trash". The aim of this study was to evaluate the effects of nitrogen fertilizer applied to corn (Zea mays L.) grown in no-tillage. The experiment was conducted at USP-São Paulo University in Pirassununga-SP/Brazil in Oxisol, clay, loam, and the randomized complete block design with ten treatments and four replicates with the standard dose of 100 kg.ha^-1 N. The treatments were: T1) Control + Gypsum, T2) Control absolute, T3) Urea, T4) Urea + Gypsum, T5) Urea + ammonium sulfate, T6) Ammonium nitrate, T7) Ammonium nitrate + Gypsum, T8) Nitrate ammonium sulfate + ammonium, T9) ammonium sulfate and T10) FASN (Fusion Amonium Sulfate Nitrate). The losses of NH3-N were determined by semi open collector according to Lara Cabezas et al. (1999) using five bases to collect in eight periods between December 20th and January 10th. It was found that the greatest losses of NH3-N occurred until the sixth day after application, in the treatments containing urea, T3 (13.5%), T4 (13.0%) and T5 (10.8%), and lower losses for the treatments with ammonium sulfate and ammonium nitrate, and the lowest value for the T-10 (8.14%). This behavior is associated with the chemical form of N,namely amide and urea and ammonium nitrate in FASN. The losses of NH₃-N can be considered low, as they were applied to the trash, because of precipitation occurred, namely 29.8 mm two days before and 32.2 mm after 4 days of cultivation. It was concluded that the major losses of NH₃-N occurred in up to six days and that FASN was the fertilizer that had the lowest NH₃-N loss by volatilization.