[en] This greenhouse study conducted on a Mediterranean Terra Rose soil, as a single crop production, heated only for anti frost, was designed to investigate the response of drip-irrigated tomatoes (Lycopersicon esculentum Mill.) to four nitrogen levels continually applied with the irrigation stream. Water containing 0, 50, 100 or 150 mgN/l and uniformly supplied with 60 and 180 mg/l of P and K, respectively, were applied two times a week. Three adjacent plants in each plot were fertigated with N¹⁵ labeled NH₄S₂O₄ (2% a.e. enrichment). For each plant the amount of water, P,K and the N¹⁵ applied through the bottles was equivalent to that amount applied through a single dripper. These treatments were compared with banded application of NH₄S₂O₄ at the rate of 400 kgN/ha that was equivalent to 100 mgN/l treatment. The resulting N application totals ranged from 200 to 600 kgN/ha.The total amount of water applied was 427mm. The results obtainedshowed that the percentage fertilizer utilization by the tomatoes was the highest in 50 mgN/l (200 kgN/ha) treatment, 100 mgN/l (400 kgN/ha) treatment, was on the second row, the percentage fertilizer utilization in 150 mgN/l (600 kgN/ha) and soil applications (400 kgN/ha) were the same and were significantly lower than the other treatments. The highest yield was achieved in the 100 and 150 mgN/l (400 and 600 kgN/ha) treatments. This experiment demonstrated that the amount of N fertilizer by applying in the irrigation water is to be recommended 100 mgN/l for tomatoes to obtain high yield in production under greenhouse conditions