Friday, 14 July 2006
107-10

Hydropedology in Action: Soil Changes After 40 Years of Wastewater Irrigation.

Charles Walker and Hangsheng Lin. The Pennsylvania State University, 420 ASI Building, University Park, PA 16802

For over 40 years, The Pennsylvania State University (PSU) has irrigated its wastewater onto both cropped and forested lands. This method of wastewater disposal has been gaining popularity in water deficit regions. However, it is not widely used in areas that have a surplus of water. PSU sprays two inches of water a week, regardless of local weather conditions. The irrigation and natural precipitation combined amount to approximately 140 inches of water per year, equivalent to tropical rainfall. Our study investigates soil changes in its morphology and functionality that have occurred during this long period of increased inputs of water. The research area has a karst geology and is dominated by rolling hills that have many small depressions that act as sinks for runoff. Soil cores were taken at 50 sites within a 16-acre field. The sites were chosen based on landscape position. The field was cropped with a corn and winter wheat rotation, which used a no-till farming practice. According to the 2nd–order soil map, the predominant soils in the field are the Hagerstown (Typic Hapludalf) and Hublersburg (Typic Hapludult) soil series. These soils are generally very-deep and well-drained that have formed from limestone/dolomite residuum. Previous studies of the area provide an estimate of original soil properties. Combinations of original and new methods were performed in this study to determine how the soils have changed over time. Soil morphological parameters including structure, horizonation and redoximorphic features were evaluated from the soil cores and in situ soil pits. Soil functional parameters including saturated hydraulic conductivity, bulk density, texture, organic matter content, aggregate stability, and infiltration rate were also evaluated to determine the longevity of the system. Preliminary results suggest that the soils have experienced a period of accelerated erosion. This was characterized by an over-thickened A horizon in the depressions and a very thin A horizon on the ridges. The soil structure has also appeared to change from granular to platy in the A horizon. Some of the depressions are showing signs of redoximorphic features at depths of less than a meter and most of the areas have increased numbers of manganese concretions. The soil functionality has also changed. Visual observations of increasing amounts of runoff are supported by the laboratory findings of increased bulk density and reduced saturated hydraulic conductivity in regions of the study area. Further studies are ongoing to comprehensively evaluate various soil changes over several decades of heavy human impacts.

Back to 1.1A Hydropedology: Fundamental Issues and Practical Applications - Theater II
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Back to The 18th World Congress of Soil Science (July 9-15, 2006)