Importance of terrain attributes in relation to the spatial distribution of soil properties at the micro scale: a case study

Micro-topography and spatial variability of soil properties influence the environmental consequences of site-specific management. This study investigated the spatial structure of soil properties in relation to the micro-topography of an agricultural field in the Canadian Prairies. The geospatial sampling scheme had 178 soil cores to a depth of 120 cm. Soil texture and soil water content (SWC) at 0-120 cm, total nitrogen (TN), total carbon (TC), and soil organic carbon (SOC) at 0-15 cm were measured and spatially interpolated using semi-variograms calculated with GS+. The correlation of terrain attributes, calculated from digital elevation models, with soil properties was also assessed. Texture was strongly spatially dependent in the surface layers, and the significance of spatial dependency declined with depth. Spatial autocorrelation of sand content declined from 96% at the soil surface (0-15 cm) to 90% at 30-45 cm, 53% at 75-90 cm. SWC, TC, TN, and SOC were similarly auto-correlated. Elevation, relative slope position, and vertical distance to channel network influenced the distribution of texture and SWC based on analysis with partial least squares, though this relationship decreased with depth. Terrain attributes are correlated with the spatial variability of soil properties and should be considered in environmental analyses at the micro-scale.