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| Titel |
Geophysical characterization of soil moisture spatial patterns in a tillage experiment |
| VerfasserIn |
G. Martinez, K. Vanderlinden, J. V. Giráldez, J. L. Muriel |
| 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 |
250021932
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| Zusammenfassung |
| Knowledge on the spatial soil moisture pattern can improve the characterisation of the
hydrological response of either field-plots or small watersheds. Near-surface geophysical
methods, such as electromagnetic induction (EMI), provide a means to map such patterns
using non-invasive and non-destructive measurements of the soil apparent electrical
conductivity (ECa. In this study ECa was measured using an EMI sensor and used
to characterize spatially the hydrologic response of a cropped field to an intense
shower.
The study site is part of a long-term tillage experiment in Southern Spain in which
Conventional Tillage (CT), Direct Drilling (DD) and Minimum Tillage (MT) are being
evaluated since 1982. Soil ECa was measured before and after a rain event of 115 mm, near
the soil surface and at deeper depth (ECas and ECad, respectively) using the EM38-DD EMI
sensor. Simultaneously, elevation data were collected at each sampling point to
generate a Digital Elevation Model (DEM). Soil moisture during the first survey
was close to permanent wilting point and near field capacity during the second
survey.
For the first survey, both ECas and ECad, were higher in the CT and MT than in the DD
plots. After the rain event, rill erosion appeared only in CT and MT plots were soil
was uncovered, matching the drainage lines obtained from the DEM. Apparent
electrical conductivity increased all over the field plot with higher increments in the DD
plots. These plots showed the highest ECas and ECad values, in contrast to the
spatial pattern found during the first sampling. Difference maps obtained from the
two ECas and ECad samplings showed a clear difference between DD plots and
CT and MT plots due to their distinct hydrologic response. Water infiltration was
higher in the soil of the DD plots than in the MT and CT plots, as reflected by their
ECad increment. Higher ECa increments were observed in the depressions of the
terrain, where water and sediments accumulated. On the contrary, the most elevated
places of the field showed lower ECa increments. When soil is wet topography
dominates the hydrologic response of the field, while under drier conditions, hydraulic
conductivity controls the soil water dynamics. These results show that when static
soil properties, e.g. clay content, are spatially uniform, ECa can detect changes in
dynamic properties like soil moisture content, characterizing their spatial pattern. |
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