Soil water erosion is influenced by several properties and is normally explained by a two step process: the breakdown of soil aggregates caused by raindrop impact and the removal of material through losses with water flow. The role of clay in the global process depends on the soil type: it may decrease aggregate breakdown by slaking and increases that by differential swelling (microcracking), but it may also affect the amount of particles in the dispersed phase, enhancing therefore the second step of the erosion process. The dispersibility of fine suspensions depends on a number of properties of the solid phase including the relative amounts of cations on the exchange sites, the mineralogical composition, the surface properties and the size of the particles, which are in turn affected by soil characteristics such as organic matter content. Most of the studies on the effect of clay on aggregate stability are related to clayey soils. The aim of this work was to evaluate the dispersibility of the clay fraction and the stability of the aggregates on two Alpine soils (Entisol and Alfisol) with low clay contents. Samples are similar for pH, subacid, and organic matter content. CEC value is 20.0 and 15.7 cmol(+)kg-1, the base saturation is however very different in the two soils and the dominant exchangeable cations are calcium in the Entisol and magnesium in the Alfisol. The Alfisol has more clay and it shows a higher ratio water to chemically-dispersible clay and flocculation value. These findings indicate that the colloidal fraction is more dispersible and more stable in the Alfisol than in the Entisol. In the aggregates the total pore volume and the pore radius decrease as a function of clay content. Both soils show a good stability of the aggregates but differences were found in the kinetics of breakdown. In Alpine soils, clay properties seem therefore to affect the breakdown caused by the compression of air entrapped inside the aggregates during wetting, but also the mobility of particles in water.

Relationship between clay properties and some physical properties in two alpine soils in piedmont (italy)

FALSONE, GLORIA;
2004

Abstract

Soil water erosion is influenced by several properties and is normally explained by a two step process: the breakdown of soil aggregates caused by raindrop impact and the removal of material through losses with water flow. The role of clay in the global process depends on the soil type: it may decrease aggregate breakdown by slaking and increases that by differential swelling (microcracking), but it may also affect the amount of particles in the dispersed phase, enhancing therefore the second step of the erosion process. The dispersibility of fine suspensions depends on a number of properties of the solid phase including the relative amounts of cations on the exchange sites, the mineralogical composition, the surface properties and the size of the particles, which are in turn affected by soil characteristics such as organic matter content. Most of the studies on the effect of clay on aggregate stability are related to clayey soils. The aim of this work was to evaluate the dispersibility of the clay fraction and the stability of the aggregates on two Alpine soils (Entisol and Alfisol) with low clay contents. Samples are similar for pH, subacid, and organic matter content. CEC value is 20.0 and 15.7 cmol(+)kg-1, the base saturation is however very different in the two soils and the dominant exchangeable cations are calcium in the Entisol and magnesium in the Alfisol. The Alfisol has more clay and it shows a higher ratio water to chemically-dispersible clay and flocculation value. These findings indicate that the colloidal fraction is more dispersible and more stable in the Alfisol than in the Entisol. In the aggregates the total pore volume and the pore radius decrease as a function of clay content. Both soils show a good stability of the aggregates but differences were found in the kinetics of breakdown. In Alpine soils, clay properties seem therefore to affect the breakdown caused by the compression of air entrapped inside the aggregates during wetting, but also the mobility of particles in water.
Geophysical Research Abstracts
06794
06794
Falsone G.; Bonifacio E.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/98210
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