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Porosity factors that control the hydraulic conductivity of soil-saprolite transitional zones

Soil Science Society of America Journal

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Abstract

Slowly permeable transitional horizons separate soil and saprolite, but these horizons cannot be identified easily in the field. The objectives of this study were to determine why the soil-saprolite transitional zone (BC and CB horizons) is slowly permeable, and to evaluate ways for identifying it in the field. Two saprolite deposits were studied in the North Carolina Piedmont. At each site, saturated and unsaturated hydraulic conductivities (Ksat and Kunsat) were measured for major horizons. Volume fractions of water-conducting pores were also compared with the changes in hydraulic conductivity with depth. Horizon mean Ksat values at both sites ranged from virtually 0 to approximately 3 cm h-1. The lowest Ksat values (<0.3 cm h-1) occurred in or near the transitional horizons that were directly below the Bt horizons. Changes in the volume of pores within or between mineral grains (termed inter/intraparticle pores) with depth corresponded to changes in both Ksat and Kunsat. In the transitional horizons, the inter/intraparticle pores were plugged with clay and this caused the horizons to have low K values. In situ measurements of Ksat with depth were the most accurate technique to use for identifying transitional zones in the field. Examination of both the soil and rock structures in pits was also an acceptable technique. Texture and consistence were not considered reliable for pin-pointing transitional horizons.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Porosity factors that control the hydraulic conductivity of soil-saprolite transitional zones
Series title:
Soil Science Society of America Journal
Volume
60
Issue:
1
Year Published:
1996
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Soil Science Society of America Journal
First page:
192
Last page:
199