Soil Hydraulic Properties Affected By Topsoil Thickness in Corn-Soybean Rotation and Switchgrass Production Systems.

Soil hydraulic properties influence many of the ecological functions of soil. The objectives of this study were to determine the influence of topsoil thickness on soil hydraulic properties for grain and perennial grass production systems. The experiment was carried out at the Soil Productivity Assessment for Renewable Energy and Conservation (SPARC) plots at the University of Missouri. Each experimental plot was planted with either switchgrass (Panicum virgatum L.) or a corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation. Plots were initially established in 1982 with varying levels of topsoil thickness (0, 12.5, 25, and 37.5 cm) on a Mexico silt loam (Vertic Epiaqualfs). Intact soil cores were collected from the plots in March 2014 by using aluminum rings (7.6 cm in diam. by 7.6 cm long) from four 10 cm depth increments to determine saturated hydraulic conductivity (Ksat), soil water retention, and bulk density (additional samples were collected from deeper depths for the 40 cm topsoil thickness plots). The Ksat was three times higher (349.7 versus 111.2 mm h-1) in the switchgrass treatment compared to the row crop treatment within the first 10 cm. Significant interactions for Ksat occurred for production system and topsoil thickness. Results show that switchgrass treatment increased saturated hydraulic conductivity compared to row crop treatment. This approach of using vegetative biofuel crops on eroded soils may be important for future production systems as demand for food and biofuel consumption increases.