Large-scale multi-configuration EMI characterization

Satellite-derived Leaf Area Index (LAI) data obtained after a two-month drought period showed narrow and undulating patterns (see lower circle), probably caused by a paleo-channel system at the upper terrace of the river Rur close to the testsite Selhausen. The influence of lateral and vertical changes of the soil properties on these patterns was investigated at ten arable fields by using multi-receiver electromagnetic induction (EMI) measurements with depths of exploration ranging from 0.3 to 1.8 m (see upper circle). The shallow apparent electrical conductivity (ECa) data were not well correlated with the observed LAI patterns, and also soil probes indicate a relatively homogeneous topsoil, probably due to agricultural management. The deep ECa data showed a strong correlation with the LAI patterns and soil probes confirmed that filled-in channels were present in the subsoil having a higher electrical conductivity (EC) due to the higher clay fraction compared to the surrounding soil with a higher sand and gravel fraction. The strong correlations between large-offset ECa data and the subsoil clay content and soil profile depth, imply that the subsoil is mainly responsible for better crop development in drought periods.

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Geoderma 261 (2016) 178–189, doi: 10.1016/j.geoderma.2015.07.015
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