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Experimental Measurement of Macropore Flow in a Silt-Loam Soil

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  . . 10.13031/2013.1918

Authors:   G. O. Brown, H. T. Hsieh, and J. Kimzey
Keywords:   preferential flow, macropore, laboratory column

The mechanics of flow in soil macropores was measured in repacked, laboratory columns. Pore diameter, length, construction, and coating, were varied along with the flow rate to allow for empirical determination of their significance. Gamma-ray tomography was used to quantify soil density before and after pore construction. Results indicated a lack of a pressure gradient within the macropores for the described laboratory conditions. At lower flows rates (15 ml/min), flow down the macropore is controlled by the water supply and not by soil pressure gradients or soil permeability. All water will radially adsorb into the soil column. For higher flow rates (60 ml/min), the flow through the column has a more uniform gradient and is controlled by soil permeability. The method of macropore construction and organic coating did not impact any results, and the size of the pore only changes results for high flow rates.

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