N03-N is readily leached from mineral soils with rain or overhead irrigation. To determine the amount of N03-N conserved with plastic mulch, `Northstar' bell pepper was grown with and without 2-mil black plastic mulch, with 0, 80, and 160 lbs/acre of preplant N. One treatment consisted of unplanted rows. At 1, 2, 3, and 5 months after planting on 26 May 1994, soil samples for N03-N analyses were taken at 0–6” and 6–12”. Not only was N03-N conserved under the mulch, but it was also enhanced. N03-N levels increased up to 595 ppm in plots with mulch, no crop, and 160 lbs N/acre. The pepper crop utilized about one-third of the nitrogen under the mulch. After 5 months, nitrate levels averaged about 6 ppm in all plots without mulch, whereas, in plots with mulch, nitrate levels averaged about 97 ppm. For most of the season nitrate were higher at 0–6 inches than at 6–12 inches, but, nearer the end of the season, nitrates in plots without mulch were nearly the same or greater at 6–12 inches than at 0–6 inches. Yields were highest with mulch and 80 lbs N/acre.