Fig. 4. Annual NO₃–N transport in subsurface flow throughout the 11-yr pre-study period (1979–1990) during which 168 kg N ha^–1 was applied annually to rotationally grazed pastures, and the 7-yr study period (1990–1997) during which no N fertilizer was applied and two watersheds were grazed and two were hayed. Each year notation is a grazing year (May–April).