Fig. 7. Effect of increasing amounts of goethite application to the artificial quartz substrate (G-0 = 0 g kg^–1; G-1 = 1 g kg^–1; G-4 = 4 g kg^–1) on soil solution pH at increasing distance from the center of the root compartment with time. Horizontal hair lines at 16 mm distance from the center of the root compartment represent the location of the nylon net (root surface). Soil solution was sampled 10, 17, 24, and 31 d after planting (DAP).