RATES OF SOIL REDISTRIBUTION ASSOCIATED WITH SOIL ZONES AND SLOPE CLASSES IN SOUTHERN SASKATCHEWAN

Abstract

The usefulness of the average slope measurements available from soil surveys in the development of regional erosional inventories depends on the relationship between the average slope measurements of the mapped area and the mean rates of soil redistribution within the areas. Using 137Cs redistribution techniques we examined the relationship between mean rates of soil redistribution and average slope characteristics at 21 areas in the Brown, Dark Brown, and Black Chernozem soil zones of southern Saskatchewan. Net soil losses averaged 5.8 t ha−1 yr−1 for areas with mean gradients between 0 and 1.5°, 7.8 t ha−1 yr−1 for areas with mean gradients between 1.0 and 3°, and 11.3 t ha−1 yr−1 for areas with mean gradients between 3.5 and 8.5°. For all three slope classes, the highest rates of soil loss were found in the Dark Brown soil zone and the lowest rates in the Black soil zone. Net soil loss alone was, however, an inadequate indicator of the rate of loss within the areas because a considerable proportion of eroded soil was deposited within the confines of the study areas. Our results indicate that a distinct rate of soil loss was associated with the average slope characteriestics of the study area, but that both net soil loss from the field and mean soil loss within the field need to be considered together if a complete erosional assessment is to be made of an area. Key words: Soil erosion, soil deposition, 137Cs redistribution, slope gradient, Saskatchewan