ALBERT

Description: Soil erosion in five Rural Municipalities of west-central Saskatchewan was assessed using cesium-137 as an indicator of soil redistribution. Native, noneroded soils across the study area were sampled to determine a baseline value for cesium-137 (2877 Bq m−2), which was used to predict the erosion of cultivated soils since the early 1960s. Soil redistribution estimates were calculated for idealized positions (upper, middle, lower) on medium-textured cultivated hillslopes, and for the total erosional portion of the hillslopes. Mean hillslope soil erosion rates were 23 ± 8 t ha−1 yr−1 for slopes with 0–3% gradient, 27 ± 9 t ha−1 yr−1 for 3–10% slopes, and 48 ± 16 t ha−1 yr−1 for 10–24% slopes, representing a soil removal of 3.8 cm, 4.4 cm, and 7.8 cm, respectively, since 1960. These soil losses represented between 27 and 67% of the topsoil and between 8 and 35% of the solum currently present within the eroding upslope areas. A significant positive correlation existed between the thickness of soil horizons and solums, and the rate of soil erosion on the upper and middle slope positions. The greatest erosion rates were determined for the upper slope positions, probably because of a dominance of wind and tillage erosion within the area. Soil erosion rates within slope classes decreased with increasing slope length, particularly on 10–24% slopes. Erosion by overland flow was considered to be of minor importance, especially on level landscapes (0–3% gradient) where erosion averaged 23 ± 8 t ha−1 yr−1. Erosion rates ranging between 23 and 48 t ha−1 y−1 occurred over approximately 2/3 of the cultivated study area. High rates of soil erosion over such a large portion of the landscape are alarming, considering that the accepted tolerable soil loss is 11.2–4.5 t ha−1 yr−1. Key words: Soil erosion, cesium-137, water erosion, wind erosion, hillslope