Friday, 14 July 2006
107-11

Modeling Soil Hydraulic Properties as a Function of Morphological Features and Land use.

Xiaobo Zhou1, Henry Lin1, ED White2, John Chibirka2, and Yuri K. Plowden3. (1) Penn State Univ, 116 ASI Bld., University Park, PA 16802, (2) USDA-NRCS, One Credit Union Place, Harrisburg, PA 17110, (3) Natural Resources Conservation Service, 216 Spring Run Road, Room 102, Mill Hall, PA 17751

Soil hydraulic properties provide critical information in runoff/erosion control, ground water quantity and quality protection, watershed management, land use planning, precision agriculture, and ecosystem functions. A dynamic soil properties database including use-dependent soil properties will benefit diverse agricultural, environmental, and ecological applications. The objective of this study is to develop a set of models to estimate soil hydraulic properties based on soil morphology, land use, and other available soil survey data. Such models would facilitate the interpretation and utilization of the National Cooperative Soil Survey (NCSS) databases for characterizing flow and transport in various soils, contribute to soil survey updates, and help the incorporation of use-dependent or dynamic soil properties into the NCSS databases. Four soil series with contrasting textures and parent materials were selected for this study. Two series (Glenelg and Joanna, Typic Hapludults) were located in Chester County, PA, representing Northern Piedmont Major Land Resources Area (MLRA) 148, and the other two series (Hagerstown, a Typic Hapludalf, and Morrison, a Ultic Hapludalf) were located in Centre County, PA, representing Northern Appalachian Ridges and Valleys MLRA 147. This study focuses on how soil infiltration rates are affected by soil properties under different land uses. 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. Apparent steady-state surface and subsurface infiltration rates were measured in situ using a set of tension infiltrometers under a series of water supply tensions (12, 6, 3, 2, 1, and 0 cm tensions). The saturated hydraulic conductivities were determined in the laboratory. Other soil properties of each site, including bulk density, soil structure, macroporosity, and root density, were also investigated for use in model development. The results showed the influence of various macropore sizes in different soils on soil hydraulic conductivity. Under low tensions (less than 3 cm), the sandstone-derived Joanna and Morrison series 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. Hagerstown series has the highest infiltration rate, and Glenelg series has the lowest with Joanna and Morrison in between. Hydraulic conductivities have the following general trend among the four land uses: woodland being the highest, pasture and urban being similar, and cropland being the lowest. The granular structure and lower bulk density of the woodland explain its rapid infiltration. The tillage practice may cause the decrease of macropores and infiltration rate in cropland. Pedotransfer functions were developed to estimate soil hydraulic in terms of soil morphology and land use as well as other soil survey data.

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