Spatial heterogeneity of soil properties and its mapping with apparent electrical conductivity

The site‐specific cultivation as part of the precision‐agriculture concept is more and more introduced into practical farming. However, soil information is often not available in a spatial resolution intrinsically needed for precision farming or other site‐specific soil use and management purposes. One approach to obtain spatially high‐resolution soil data is the non‐invasive measurement of the apparent electrical conductivity (EC a ). In this study, we recorded the EC a on three fields with an EM38 (Geonics, Canada). The EC a data were compared with (1) ground truth data obtained by conventional drilling, (2) traditional soil maps (large scale, ≤1:5,000), (3) the growth and yield of corn. The temporal variability of the EC a due to varying soil moisture and temperature was taken into account by repeated measurements of the same fields and subsequent averaging of the EC a values. Significant correlations (r² = 0.76) were found between the mean weighted clay content (0–1.5 m) and the EC a . Furthermore, in soils with differently textured layers, EC a was used to estimate the thickness of the uppermost loess layer. A comparison of EC a and large‐scale soil maps reveals some pros and cons of EC a measurements. The main advantages of EC a recordings are the high spatial resolution in combination with low efforts. Yet, the EC a signal is no direct measure for a soil type or unit. Depending on the variability of substrates and layering, the EC a pattern can be a precise indicator for the spatial distribution of different soils. A strong conformity of the spatial variability of plant growth (derived from orthophotos and yield maps) and EC a patterns within a field indicates that the EC a signal per se— without conversion to traditional soil parameters—integrates the effects of various soil variables that govern soil fertility. Altogether, EC a surveys can be a powerful tool to facilitate and improve conventional soil mapping.