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Evaluation of Methods to Estimate Macropore Characteristics in Montmorillonitic Clay Soils

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

Citation:  Pp. 233-236 in Preferential Flow, Water Movement and Chemical Transport in the Environment, Proc. 2nd Int. Symp. (3-5 January 2001, Honolulu, Hawaii, USA), eds. D. D. Bosch and K. W. King. St. Joseph, Michigan: ASAE  701P0006.(doi:10.13031/2013.2125)
Authors:   W.J. Rawls, Y.A. Pachepsky, and H.S. Lin
Keywords:   macropores, macroporosity, saturated hydraulic conductivity, clay

Macropores contribute to the rapid movement of water and solutes through the soil. Rawls et. al. (1993) developed methods based on fractal geometry for estimating the macropore saturated hydraulic conductivity for no-till soils. These procedures required a measured areal macroporosity or a measured areal macroporosity and a measured radius of the largest macropore. The objective of this study was to test these procedures on montmorillonitic clay soils. The soil survey macroporosity classes were highly correlated with the measured macroporosity. The equation for predicting macroporosity based on the largest macropore radius gave poor results. The macropore saturated hydraulic conductivity prediction equations based on a measured macroporosity and the radius of the largest macropore gave good results; however, the constant had to be reduced by about a factor of 10.

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