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Fig. 3. Variation in N uptake by corn in the three management treatments: (i) barley followed by corn under no-tillage (Barley-NT), (ii) barley followed by corn under a spring plowing and secondary tillage operation (Barley-CT), (iii) barley under-seeded with red clover that was plowed down in the following spring and plots planted to corn (Barley + RC-CT) (averaged over landscape positions in the 0N plots) during the 1997, 1998, 1999, and 2001 growing seasons. The vertical bars indicate the standard error.