Three-layered soil maps based on sensor measurements

Principles for on-going 3-D mapping projects, from field to catchment scale, of arable land in Sweden are outlined. The procedure uses proximal soil sensors and terrain attributes. Mapped areas have a pixel size of 10x10 m and consist of 2-3 layers in the top 0.8 m of the soil. As an example, the 3-D clay content map for an 800 ha catchment is presented. Accuracy was best for the topmost layer (RMSE=3.7% clay) and decreased for each layer downward. The deepest layer had high and rather homogeneous clay content and model calculations were poor. The procedure will be tested in other areas with more variable soil type and clay content.