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| Titel |
Effect of antecedent soil-water content on aggregate stability and erodibility of a loess soil |
| VerfasserIn |
J. Vermang, V. Demeyer, W. M. Cornelis, D. Gabriels |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029497
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| Zusammenfassung |
| Soil erosion processes are affected by the erodibility of the soil and by the erosivity of the
rain. Aggregate stability is commonly considered as the most significant soil physical
property that determines soil erodibility. Both aggregate stability and soil erodibility are
commonly considered to be constant properties, without taking into account the influence
of time-dependent parameters, such as antecedent soil-water content (θa), being
the soil-water content prior to the rainfall. The effects of rain characteristics and
invariant soil properties such as texture and organic matter content on soil erosion
processes are well documented. However, the effect of antecedent soil-water content on
aggregate breakdown, seal formation and subsequent soil erosion is much more
disputable as opposing effects have been reported. The objectives were to determine
the effect of θa on aggregate stability, seal formation, runoff and soil loss. Lab
experiments were conducted on a Belgian silt loam soil. Air-dried soil aggregates were
subjected to antecedent soil-water contents of 0.04 (air-dry aggregates), 0.12 and
0.19 m3 m-3. Aggregate stability was determined according to the ‘dry and wet
sieving’ method of De Leenheer and De Boodt (1959). The method starts from fixed
aggregate fractions obtained from dry sieving which subsequently are prewetted
and undergo a wet sieving. Runoff and soil loss was determined by means of a
laboratory rainfall simulator, consisting of a rotating circular water tank, which is
located at 3.20 m height and which is supplied with 90 glass capillaries serving as
drop formers. A positive relationship between antecedent soil-water content and
aggregate stability was found. This can be attributed to a decrease in slaking forces.
On the soils with highest antecedent soil-water content an increase in aggregate
stability due to prewetting prevented aggregate breakdown. As such, no seal was
formed and no runoff occurred. The highest total runoff values were observed for the
intermediate θa, while intermediate amounts of total runoff were noticed for the air-dry
aggregates. Soil loss, however, showed a different trend: highest values were found for
the lowest θa, intermediate values for the intermediate θa and no soil loss for the
highest θa. We further observed that θa had no influence on the final runoff rates and
on the final infiltration rate through the soil surface. In using a water discharge
and stream power equation to predict sediment transport, we found a decreasing
erodibility with increasing θa. We therefore suggest including θa as an additional
variable to assess soil erodibility in deterministic event-based water erosion models. |
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