Feasibility study on the potential of electrical conductivity sensor Veris® 3100 for field mapping of topsoil strength

•Use of soil electrical conductivity for delineating topsoil strength.•Promising relation between electrical conductivity and the state of soil strength.•Weak correlation between soil electrical conductivity and dry bulk density.•Justification of the observations with theoretical model of electrical conductivity.

With advances in technology for precision agriculture, numerous attempts have been made towards development of on-the-go sensors for measuring soil compaction. Most of the on-the-go sensors developed so far have been mechanical sensors providing a soil strength parameter that can be related to degree of soil compactness. In this study, a commercial electrical conductivity sensor (Veris® 3100) in combination with a previously developed combined horizontal penetrometer (equipped with a dielectric sensor for water content) were tested in a field in order to examine whether the apparent electrical conductivity (ECa) within the 0–0.3 m depth (ECa-shallow) could be helpful in detecting the topsoil strength (here the horizontal penetrometer resistance). Interpolated field maps of horizontal penetrometer resistance (PR), volumetric water content (θv) and ECa showed comparable patterns within some areas (but not over the field). No significant correlation (but a negative trend) was found between ECa and dry bulk density. A significant correlation between ECa and PR/θv (a previously proposed water content-independent PR) was found (R2 = 0.37, P < 0.0001). However, ECa was strongly affected by soil water content and texture. It was concluded that PR may be indirectly related to ECa through θv, which greatly affects both ECa and PR. The results suggested that the EC sensor could potentially be helpful for detecting zones of high soil strength (i.e. high PR/θv). Further studies are suggested to address whether ECa is better related to the state of soil compaction at dry state of soil due to more significant effect of soil–soil electrical conductivity.