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Mapping Clay Content across Boundaries at the Landscape Scale with Electromagnetic Induction

^a Helmholtz Centre for Environ. Research-UFZ, Dep. of Soil Physics, Theodor Lieser Str. 4, 06120 Halle (Saale), Germany
^b ZALF-Leibniz Centre for Agric. Landscape Res., Institute of Soil Landscape Research, Eberswalder Str. 84, 15374 Müncheberg, Germany and Univ. of Potsdam, Institute of Geoecology, PO Box 601553, D-14415 Potsdam, Germany
^c GSF-National Res. Centre for Environment and Health, Institute of Biomathematics and Biometry, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany
^d ZALF-Leibniz Centre for Agric. Landscape Res., Institute of Soil Landscape Research, Eberswalder Str. 84, 15374 Müncheberg, Germany

View larger version (44K): [in this window] [in a new window]   Fig. 1. Apparent electrical conductivity (EC) measurement points and fields investigated for method comparison.

View larger version (10K): [in this window] [in a new window]   Fig. 2. Workflow for electromagnetic induction measurement (EMv) to clay mapping: (a) no correction for influence of land use and time; (b) fieldwise calibration; and (c) nearest neighbors EMv correction.

View larger version (15K): [in this window] [in a new window]   Fig. 3. Semivariograms for electromagnetic induction (EMv) measurements: (a) variograms for two fields compared with regional semivariogram after electrical conductivity (EC) correction; and (b) regional semivariogram with and without EC correction.

View larger version (67K): [in this window] [in a new window]   Fig. 4. Comparability of multiple electromagnetic induction (EMv) measurements: I. Reproducibility of electrical conductivity (EC) measurements.

View larger version (51K): [in this window] [in a new window]   Fig. 5. Comparability of multiple electromagnetic induction (EMv) measurements: II. Influence of time of measurement on electrical conductivity (EC) measurements.

View larger version (21K): [in this window] [in a new window]   Fig. 6. Comparability of multiple electromagnetic induction (EMv) measurements: III. Influence of time and cultivation on electrical conductivity measurements normalized to 25°C (EC25). Each symbol represents one spatial point and its EC25 signal at Date 1 (x axis) vs. the measurement at Date 2 (y axis).

View larger version (11K): [in this window] [in a new window]   Fig. 7. Comparison of methods to correct electromagnetic induction (EMv) measurement of electrical conductivity normalized to 25°C (EC25) for influences of time and cultivation with regard to prediction of soil clay content.

View larger version (72K): [in this window] [in a new window]   Fig. 8. Discontinuities of soil clay content predicted by measurements of electrical conductivity (EC) on the boundaries between landscape units.

View larger version (17K): [in this window] [in a new window]   Fig. 9. Dependence of RMSE for clay content prediction by measurements of electrical conductivity (EC) on the number of calibration points.

View larger version (69K): [in this window] [in a new window]   Fig. 10. Map of estimated clay content of the Klostergut Scheyern using the nearest neighbors electromagnetic induction measurement (EMv) correction method.