Selection and establishment of Alberta agricultural soil quality benchmark sites

Forty-three benchmark sites were established to monitor soils across the agricultural regions of Alberta. Soil chemical and physical properties were examined in an initial pedological investigation in 1997. This paper describes site selection and presents results from the initial pedological investigation. Ninety-five percent of the chosen sites were representative of their provincial ecodistrict, with only two profiles being darker and higher in organic carbon than expected. The majority of selected sites were gently undulating loam soils on morainal parent materials in the dryland regions of Alberta. Soil texture, cation exchange capacity, calcium carbonate content, and soil pH reflected regional differences in quaternary geology and agricultural practices across Alberta. Southern Alberta was characterized by high pH, sandier-textured soil profiles, whereas the Peace Lowlands, being derived from marine shale deposits, exhibited finer soil textures and higher cation exchanges capacities. Owing to climatic and vegetative differences, organic carbon levels were significantly greater in northern Alberta compared with the south, but were found to differ based on soil horizon and slope position. Upper slopes typically had lower organic carbon levels, particularly in the A horizon. Similar results were observed for total soil N, although other soil nutrients differed in relation to soil properties, slope and ecoregion. Data collected will provide: (a) the basis for a detailed Alberta soil quality assessment, (b) data for future modeling efforts, and (c) data necessary to identify temporal changes in soil properties, yield and management relationships.