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Nitrogen (N) leaching below the crop-rooting zone represents not only a valuable loss of nutrients for the plant, but also a potential pollution source of groundwater. The objective of this work was to quantify leaching losses of native N and that derived from fertilizer in an Oxisol that was cultivated with sugarcane (Saccharum officinarum) during the crop plant cycle. The sugarcane was planted and fertilized with urea in the planting furrow, with 120 kg ha -1 of N. In order to determine the fate of the fertilizer -N, four microplots with 15 N enriched fertilizer were installed. Input and output of N at the depth of 0.9 m were quantified from the flux density of water and the N concentration in soil solution. During the evaluation period the rainfall was 141 mm less than the historical average (1,315 mm), and the climate was drier than normal in January. The average concentration of mineral N in soil solution was 1.8 mg L -1 . The abundance of 15 N was very high at the beginning (first week) of the assessment period and remained approximately constant (0.453 atom% of 15 N) until the end of the period. The internal drainage was 91 mm of water and the N leaching loss was 1.1 kg ha -1 of N, with only 54 g ha -1 derived from fertilizer. Therefore, under high demand of N by the crop in a system without burning before planting, the leaching of N was not considerable, mainly because the surplus of water between the months of December and March was lower than expected and also because the extraction of nitrogen by the crop was high. Key words: Saccharum spp., sustainability, solute transport, environmental quality, pollution Nitrogênio lixiviado num Latossolo cultivado com cana-de-açúcarRESUMO: A lixiviação de nitrogênio (N) abaixo da zona radicular representa uma valiosa perda do nutriente para as plantas e uma fonte potencial de poluição do lençol freático. Quantificaram-se as perdas de N por lixiviação num Latossolo Vermelho Amarelo cultivado com cana-de-açúcar (Saccharum officinarum) durante o ciclo agrícola de cana-planta. A cultura foi implantada e fertilizada no sulco com 120 kg ha -1 de N-uréia. Para conhecer o destino do fertilizante, foram instaladas quatro microparcelas onde o fertilizante era marcado com o isótopo 15 N. As entradas e saídas de N a 0,9 m de profundidade foram quantificadas diariamente pela densidade de fluxo de água e a concentração de N da solução no solo. No período de avaliação, a precipitação pluvial foi 141 mm menor que a média histórica (1.315 mm) sendo janeiro mais seco que o normal. A concentração de N mineral média foi 1,8 mg L -1 . A abundância de 15 N foi superior à abundância natural do isótopo, especialmente no início do período de avaliação, permanecendo logo constante (0,453% de 15 N). A drenagem interna foi de 91 mm de água e a perda por lixiviação foi 1,1 kg ha -1 de N com apenas 54 g ha -1 derivados do fertilizante. Portanto, com elevada demanda de nutrientes e elevada incorporação de restos culturais, não foram registradas perdas apreciáveis de N por lixiviação d...