Using Regionalised Variables to assess Field-scale Spatiotemporal Variability of Soil Impedance for different Tillage Management

To assess the effect of tillage on soil impedance, the knowledge of spatial and temporal variability in the soil is necessary. Geostatistical approaches are very useful for characterisation of space–time variability of soil parameters. In this study, geostatistics were applied to soil impedance data, in order to study the effects of two soil tillage depths: mouldboard ploughing to 40–45 cm and surface disc harrowing to 20–25 cm. Soil strength was measured from January to April 2001 at 3·5 cm depth increments, from the surface to a depth of 52·5 cm. Mean gravimetric water content was also measured for two depths (0–25 and 26–50 cm). In order to treat the spatial–temporal variability of soil impedance, the multiple random function models approach was applied, where the set of the recording dates is treated as a realisation of inter-correlated random functions. The variography revealed a high temporal correlation between the soil strength measured at different depths over time. For each survey, the three-dimensional interpolated maps showed random variations of soil impedance on the surface, mostly affected by soil water content, and a clear stratification along the vertical profile. However, no discrimination between the strips differently managed was possible to be detected on three out of four dates.