The aim of this work was to optimize the application of nitrogen fertilizer in a melon crop (Cucumis melo c.v. "Sancho") in order to reduce the nitrate lixiviation. This experiment was carried out from May to September 2005 in the field station La Entresierra, Ciudad Real, Spain. The characteristic soil texture of this area is sandy and clay-sandy, which presents very low variability in the first 60 cm of depth. Deeper than this a fragmented petrocalcic layer is localized. The experiment had a random block design, it was watered with 100% of ETc and the treatments consisted in four nitrogen doses: 0 (A0), 60 (A1), 90 (A2) and 120kg N ha^-1 (A3). The levels of nitrates in the soil profile were obtained by means of suction cups located between two plants to 32.5 cm of watering line and 60 cm of depth. Between the two following plants, three access tubes to the probe Diviner were installed at 12.5, 37.5 and 62.5 cm distance from the watering line to determinate the soil humidity. The results showed a clear correlation between the increments of nitrogen leached and fertilizer doses bigger than A1 treatment, as well as with the distance to the watering line. The nitrogen uptake by melon plants and the melon quality parameters are full discussed related to these observations.