Soil hydraulic properties influenced by stiff-stemmed grass hedge systems

The effectiveness of stiff-stemmed grass hedge systems in controlling runoff and soil erosion is influenced by the water transport properties of the soil under grass hedge management. This study evaluated soil hydraulic properties within a grass hedge system 10 yr after establishment. The study was conducted at the USDA-ARS research station near Treynor, IA in a field managed with switchgrass (Panicum virgatum) hedges. The soil was classified as Monona silt loam (fine-silty, mixed, superactive, mesic Typic Hapludolls). Three positions were sampled: within the grass hedges, within the deposition zone 0.5 m upslope from the grass hedges, and within the row crop area 7 m upslope from the hedges. Intact soil samples (76 by 76 mm) were taken from the three positions at four depths (100-mm increments) to determine saturated soil hydraulic conductivity (K-sat), bulk density (rho(b)) and soil water retention. The grass hedge position had significantly greater (P < 0.05) macroporosity than the row crop and deposition positions in the first two depths and greater than the deposition position in the last two depths. The K-sat within the grass hedge (668 mm h(-1)) was six times greater than in the row crop position (115 mm h(-1)) and 18 times greater than in the deposition position (37 turn h(-1)) for the surface 10 cm. Bulk density and macroporosity were found to provide the best two-parameter regression model for predicting the log-transformed K-sat (R-2 = 0.68). These results indicate that grass hedges significantly affected soil hydraulic properties for this loess soil.