The present study aimed to evaluate the effect of the dose and source of nitrogen (N) fertilizers on plant vegetative growth, productivity, and quality of onion bulbs in the conditions of the Brazilian Cerrado. For this purpose, the experimental design included three doses of N (50, 100 and 150 kg N ha-1, corresponding to 50, 100 and 150% of the recommended dose, respectively), and two N sources (urea, 45% of N; and and ammonium sulfate, 20% of N). It was verified that the increment of N doses resulted in more vigorous plants and, consequently, in greater productive gains. In addition, it was found that the use of ammonium sulfate provided a 37.2% increase in bulb weight and total productivity and a 59.6% increase in the productivity of Class III marketable bulbs compared to urea. In addition, it was concluded that, for onion cultivation under tropical conditions, like in the present study, the use of a dose equivalent to 150% of the recommendation for onion provides better productive performance of the crop, especially when associated with the use of sulfate ammonium as N source.
Keywords: Allium cepa L., ammonium sulfate, urea, bulb quality