Long-term solute redistribution in relation to landscape morphology and soil distribution in a variable glacial till landscape

摘要

Landscape delineation based on soilslope associations with similar patterns of solute redistribution would allow for better agro-environmental land management. Long-term redistribution of solutes was examined in relation to topographic variables and static soil properties in a glacial till landscape near Miniota, Manitoba. Static soil properties that were the best predictors of solute redistribution included CO_3, Ahor, Solum and OrgC. Temporal variability overshadowed the influence of topographic variables and static soil properties on dynamic solute redistribution within the crop rooting zone (i.e., 120 cm). Topographic variables (relative elevation, topographic index, contributing area) and static soil properties (A horizon depth, solum depth, Ahorizon organic carbon) were correlated to SO_4~(2-) and NO_3~- redistribution. An unexpected result was that more statistically significant relationships were found between these parameters and solute redistribution below 120 cm rather than within the root zone. Very low NO_3~- concentrations were found in the rooting zone at most sample positions, indicating that crop demand during recent growing seasons matched or exceeded supply. Accumulations of NO_3~- below the rooting zone indicated that deep percolation of NO_3~- has been an important process over the longer term throughout the upper and mid slope positions of this landscape. A lack of NO_3~- accumulation in one lower-toe position and the depression indicated that excess NO_3~- in these profiles may have been leached into the groundwater and/or removed via denitrification or simply may not have accumulated. There appears to be utility in using static soil properties and topographic variables as indicators of dynamic processes of solute redistribution, however, a priori knowledge of soil-landscape relationships and an understanding of associated pedogenic processes and hydrologie regimes are required to achieve sensible results.