Fig. 9. Temporal changes in NO₃–N concentrations in water collected from lysimeters and piezometers at D, S, T, and R positions in Watersheds 1 and 2 (see Fig. 1). Open symbols denote suction-cup lysimeters, black-filled symbols denote piezometers in loess, and gray-filled symbols denote piezometers near the till contact. Depths of monitoring (meters below surface) are noted above each plot. Nondetectable concentrations (<1 mg L^-1) are plotted at zero. Symbols overlap in some plots. Some installations did not yield water samples every month (see Table 2).