Geostatistical homogenization of soil conductivity across field boundaries

The use of the apparent electrical conductivity (ECa) to map soil characteristics such as clay content is mostly limited to the field scale because of field-specific random effects e.g. due to different management history. Soil conductivity maps that are continuous across field boundaries are however a prerequisite for mapping soil properties at the landscape scale. Therefore we propose a geostatistical framework for the homogenization of soil data across field boundaries, i.e. for "matching" adjacent ECa surveys together. It consists of transforming field-specific data by minimizing the discontinuity error of an interpolator of the target variable on adjacent fields. We apply the homogenization technique in a case study in Central Germany, which shows that the proposed scaling technique is able to remove field-specific effects. A simulation study with known, simulated field-specific effects is performed to test the validity of the technique. It confirms that the algorithm is able to reduce discontinuity errors, yielding a homogenized ECa surface that is continuous across field boundaries. It identifies linear scaling parameters between fields apparently with a small bias. Spatial decorrelation between adjacent fields may lead to significant estimation uncertainties, depending on the distance between ECa survey traces and measurement error. (C) 2007 Elsevier B.V. All rights reserved.