Impact of a subsurface volcanic-ash layer on the properties of a southern Alberta soil with shallow water table

Abstract

Two soils from a large depressional area, one with (AL) and one without (NL) a volcanic-ash layer, were investigated to determine the effect of the ash layer on soil properties. The soil parent materials, including the ash layer, were deposited in a lacustrine environment. Both soils had well-developed A and B horizons with secondary salinity. The AL soil contained less Na in the B horizon than the NL soil, resulting in a soil classification of salinized Gleyed Solonetzic Dark Brown Chernozem at the AL site and salinized Gleyed Dark Brown Solonetz at the NL location. Saturated hydraulic conductivity and moisture retention values indicated that the volcanic-ash layer enhanced the depth of effective drainage. This was supported by greater rooting depth, weaker B horizon structure, lower salinity, and dominance of different ions in the upper solum of the AL than in the NL soil. The distribution of soluble ions in the profiles indicated that the ash layer had negligible impact on the height of capillary rise. Lower soluble ion contents in the lower profile of the AL than the NL soil were attributed to the presence of an indurated or cemented layer between the water table and the ash layer in the AL soil. Key words: Soil properties, volcanic-ash, water movement, soluble salt movement, indurated horizon