Proper N-fertilizer and irrigation management can reduce nitrate leaching while maintaining productivity, which is critical to enhance the sustainability of vegetables production on vulnerable soils. This study compared different methodologies for estimating nitrate leaching in mulched zucchini, pepper and tomato production systems. N-fertigation levels were 100% and 150% of recommended rates corresponding to 164 and 246 kg N/ha for zucchini vs 220 kg and 330 N/ha for pepper and tomato, respectively. Irrigation was either applied at fixed daily rate or based on threshold values of sensors placed in production beds. Four different methods were used to evaluate the interactive effects of N rate and irrigation management on N leaching. Suction cup lysimeters were installed at 30, 60 and 90 cm and sampled weekly, 24h after applying a partial vacuum (65 kPa). Drainage lysimeters were constructed using barrels cut in half lengthwise (volume=104 L) and barrels were placed 70 cm below the bed surface and samples were collected weekly using a partial vacuum (20 kPa). Resin traps consisted of 7.5 cm wide and 10 cm tall PVC pipe filled with a representative soil along with 80 g resin material and traps were placed at 60 (2004) or at 30, 60 and 90 cm (2005). N was determined at the end of the season. Representative soil samples were collected biweekly at 0-30, 30-60 and 60-90 cm depth and analyzed for nitrate. Based on drainage lysimeters N leaching ranged from 5 to 62 kg/ha for the medium and high N rates, and nitrate concentrations were similar compared to those for suction cup lysimeters. Most of the leaching occurred during the beginning of the season when both crop nutrient interception capacity and N demand were limiting. Results show that sound irrigation management is essential to minimize N leaching.