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Preferential Flow in Pastures on Benchmark Soils in West Virginia

Harman, Michael B.1; Thompson, James A.1; Pena-Yewtukhiw, Eugenia M.1; McDonald, Louis M.1; Beard, Jared2

Soil Science:
doi: 10.1097/SS.0b013e318229344d
Technical Article
Abstract

Preferential flow is a mechanistic description of irregular water movement in a soil profile where part of the soil matrix is bypassed during periods of infiltration and percolation. Although a common phenomenon, there is little research specific to West Virginia soils, particularly those under pasture management. To identify the active preferential flow pathways, FD&C blue no. 1 dye solution was applied in a ponding application to 24 pedons representing three different benchmark soil series common to pastures in eastern West Virginia. Sites were excavated 2 days after the dye application to reveal the flow paths. Digital images of the dye-stained soil profiles were taken to identify the active flow pathways and analyzed to determine if the movement of the dye appeared to be preferential. A paired t test was used to compare the stained areas of adjacent horizons within each plot to determine if the extent of stained soil between observed horizons was statistically different. Statistically different stained pixels percentages were identified in every research plot. Overall, the percentage of stained pixels was significantly different in 76% of the adjacent horizons, and irregular wetting fronts were identified in every research plot. Dye patterns indicated zones of both increasing and decreasing subsurface staining. Changes in staining patterns often occurred at or near observed horizon boundaries. This research supports the qualitative identification of preferential flow as the dominant means of water movement through the soil profile, which may have implications for the transport of surface applied nutrients or contaminants into deeper soil layers and/or groundwater.

Author Information

1Division of Plant and Soil Sciences, West Virginia University, Morgantown, WV 26506-6108. Dr. James A. Thompson is corresponding author. E-mail: james.thompson@mail.wvu.edu

2US Department of Agriculture, Natural Resources Conservation Service.

Received December 29, 2010.

Accepted for publication June 14, 2011.

Financial Disclosures/Conflicts of Interest: None reported.

© 2011 Lippincott Williams & Wilkins, Inc.