Monday, November 13, 2006

Characterization of Soil Hydraulic Properties from Morphological Features and Land Use.

Xiaobo Zhou, The Pennsylvinia State University, 116 ASI Building, University Park, PA 16802, Hangsheng Lin, Pennsylvania State Univ., University Park, PA 16802, and Ed White, USDA-NRCS, One Credit Union Place, Ste 340, Harrisburg, PA 17110.

The estimation of soil hydraulic properties is a critical step in understanding and quantifying water flow and solute transport in the vadose zone, and their knowledge is essential for runoff/erosion control, ground water quantity and quality protection, watershed management, land use planning, precision agriculture, and ecosystem functions. Soil hydraulic properties are affected by soil properties and land use, hence a dynamic soil properties database including use-dependent soil properties will benefit diverse agricultural, environmental, and ecological applications. Our study characterizes and compares the surface and subsurface hydraulic properties soil properties of various soil series under different land uses, using in situ and laboratory measurements. Four soil series with contrasting textures and parent materials were selected. For each soil series studied, four distinct land uses (woodland, pasture, cropland, urban) were chosen to investigate the impacts of land use on soil hydraulic properties. The soil core samples were collected at each infiltration site to determine surface and subsurface saturated hydraulic conductivities in the laboratory.  Other soil properties of each site, including initial soil moisture, bulk density, soil structure, macroporosity, and root density, were also investigated to help understand and interpret the hydraulic properties difference among different soil series and land use, as well as their temporal changes.The results showed the influence of various macropore sizes in different soils on soil hydraulic conductivity. The sandstone-derived Joanna and Morrison series generally had considerable higher water conductivities than the schist-derived Glenelg. Glenelg soil has a platy structure that inhibits infiltration as compared to the Morrison sub-angular blocky structure causing more infiltration. The infiltration rates in spring season were generally greater than those in fall season, particularly in cropland.