Preferential flow in a clayey coastal plain soil as affected by tillage

A 4-year study was conducted to investigate tillage systems effects on soil physical properties and preferential flow in a clayey Coastal Plain soil. The systems no-till (NT), fall moldboard plow-spring disk harrow (MB) and fall chisel plow-spring disk harrow (CP) were used in a winter wheat, summer grain sorghum rotation. Bulk density, saturated hydraulic conductivity, and soil moisture retention were determined on soil samples collected from the no traffic interrow areas of the plots. A rainfall simulator was used to directly measure surface runoff and indirectly measure infiltration. Examination of changes in the top soil zone (2.5-10.1 cm) showed that, after 1-1/2 years of tillage treatment and thereafter, the NT interrow top soil zone had significantly greater bulk density, lower saturated hydraulic conductivity, and held more water than the same soil zone on the other two treatments. The rainfall simulator work showed greater infiltration into and less surface runoff from the NT treatment than for the other treatments (despite the measured lower hydraulic conductivities of the NT interrow areas). This was attributed to preferential flow through cracks/slots in the crop row areas which survived intact on the NT plots.