Effect of structure and texture on infiltration flow pattern during flood irrigation

Understanding the flow pattern of water and solute in subsurface soils is critically important in the fields of agricultural and environmental sciences. Dye tracer tests using a flood irrigation of Brilliant Blue FCF solution (5 g l^-1) and excavation method was performed to investigate the effect of texture and structure on the infiltration pattern at three different field soils developed from granite (GR), gneiss (GN) and limestone (LS). The GR soil showed a homogeneous matrix flow in the surface soil with weak, medium granular structure and a macropore flow along pegmatitic vein and plant root in C horizon. The surface horizon (A1) of GN soil with moderate, medium granular structure and many fine roots had matrix flow. The fingering occurred at the interfaces of sandy loam A horizon and loamy sand C horizon in GR soil and loam A1 horizon and sandy loam A2 horizon in GN soil. The LS soil with strong, coarse prismatic structure and the finest texture showed a macropore flow along cracks and had the deepest penetration of the dye tracer. The macropore (crack and vein), layer interface and plant root induced the preferential flow in the studied soils.