Porosity of Surface Soil Aggregates at Various Moisture Contents1
- W. B. Voorhees,
- R. R. Allmaras and
- W. E. Larson2,3
Porosity of individual surface soil aggregates at moisture contents ranging from saturation to air-dry was determined by glass bead displacement. Measurements were made on aggregates having a diameter range from 0.5 to 10 mm at air-dry moisture content and 2.0 to 10 mm at suctions ≤ 15 bars. The coefficient of variation for a determination of aggregate density (g cm-3) ranged from 1 to 11% depending on diameter and moisture content. The major contributor to precision loss was heterogeneity of soil aggregates and not precision errors of the method.
More than a 50% decrease in specific total pore volume (cm3 g-1 of oven-dry aggregate) upon desorption from saturation to air-dry was found for three aggregate sizes each from a Chernozem and a Chestnut soil. In both soils, the percentage of pores having diameters > 29 µ increased as aggregate diameter increased. The volume fraction of air at a given moisture content increased as the diameter of aggregate increased. For all aggregate sizes, the volume fraction of air was ≥ 0.10 at 0.33 bar suction. The two soils exhibited different types of shrinkage curves.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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