The objective of this study was to evaluate the influence of addition of ammonium sulfate in mixture with urea on the volatilization of NH3-N. An experiment was carried out under controlled laboratory conditions at the Soil and Plant Nutrition Department (ESALQ/USP). The experimental design was completely randomized with five replications and five treatments. Each treatment was obtained by the mixture of urea (330 mg) with ammonium sulfate at different rates (0, 75, 150, 225 and 300 mg). The fertilizer mixtures were applied on the surface of soil (Latossolo Vermelho distrófico, medium/sandy texture) in plastic pots (400 cm³). Volatilized NH3-N was collected on the 3rd, 8th, 15th and 23rd day after incubation in a flask containing sulfuric acid and methyl orange indicator. Variables that influence the quality of the fertilizer mixture, as hygroscopicity, granulometry, and rest angle were also evaluated. NH3-N volatilization depends on the soil pH. The mixture of urea (330 mg) with ammonium sulfate (300 mg) reduced the losses of NH3-N significantly without affecting the mixture quality, in relation to the evaluated physical and chemical attributes. This mixture presented technical and agronomic efficiency for the proposed objective.
nitrogen sources; ammonia losses; fertilizers mixture