Fig. 1 Mean root density (roots cm^-2) as observed with minirhizotrons. Data from various depths (15, 45, and 80 cm), positions relative to the maize row (0–67, 135–202, and 337–402 mm), and years (1994, 1995, and 1996) are shown. Symbols and lines represent observed means and non-parametric LOESS fits, respectively