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This article in SSSAJ

  1. Vol. 58 No. 2, p. 294-303
    Received: Feb 17, 1993

    * Corresponding author(s):
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Nondestructive Determination of Hydrogeometrical Characteristics of Soil Macropores

  1. D. Wang,
  2. J. M. Norman ,
  3. B. Lowery and
  4. K. McSweeney
  1. Department of Soil Science, 1525 Observatory Drive, Univ. of Wisconsin, Madison, WI 53706-1299



Hydrological and geometrical parameters of macropores are essential for modeling water and solute transport through soils containing macropores. This study was conducted to develop a fast and nondestructive technique for determining the hydrological and geometrical characteristics of soil macropores. We measured the rate of water flowing into ant and earthworm burrows with a macropore infiltrometer and estimated burrow diameter, volume, and depth from the measured flow rate and a water flow model. To evaluate the estimated burrow parameters, we made castings of the ant and earthworm burrows with a dental plaster. The burrows had similar diameters (2.1 mm for laminar flow; 2.9 mm for turbulent flow) but different volumes and depths (281-cm3 volume and 0.60-m depth for ant burrows; 210-cm3 volume and 0.82-m depth for earthworm burrows). This technique is reasonable for ant burrows because the root mean square difference (RMSD) between casting and infiltrometer-calculated volumes is 17%; however, errors are larger for earthworm burrows (RMSD is 73%). Saturated soil matrix hydraulic conductivity (Ks) estimated from the infiltrometer measurement of earthworm burrows were comparable to matrix Ks of the bulk silt loam. The matrix Ks values estimated for ant burrows were about eight times smaller than matrix Ks of the bulk sandy soil. Such large decrease in Ks is probably caused by infilling of burrow walls by ants with fine materials. Combining the macropore infiltrometer measurements with the model is a useful means of estimating the hydrological and geometrical parameters of ant and possibly earthworm burrows.

Research supported by USDA-CSRS.

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