Fig. 2

Schematic of the experimental set-up. Each unit of the RadiMax facility had a V-shaped bottom. Minirhizotrons were overlain on the bulkheads at 0.25 m intervals, sloping from the edge towards the middle of the facility. A subsurface tracer supply system involved 15 tracer pipes, set next to every second minirhizotron. The crop rows above the tracer pipes were labeled crop rows, and those above minirhizotrons were neighbor crop rows. A subsurface irrigation system was established along the bulkheads, enabling irrigation at ten soil depths separately