Fig. 2. Concentrations of NO₃–N in lysimeter leachate during the period October 1992–April 1994, as affected by a spring-seeded (1992) ryegrass cover crop (incorporated in May 1993). Statistical differences are indicated by ** (0.01), * (0.05), and + (0.10). NS = not significant. Data points without symbols had only one sample for one of the treatments.