Tillage Erosion

The translocation of soil by tillage varies greatly within landscapes as a result of several factors. These factors include the design and operation of tillage implements and the topographic and soil properties of landscapes. The consequence of this variation in translocation is net soil redistribution within landscapes, i.e. tillage erosion. Typically, tillage results in the progressive downslope movement of soil, causing severe soil loss on upperslope positions and accumulation in lowerslope positions (Fig. 2). Tillage erosion is expressed similarly to wind and water erosion, i.e. a change in soil mass per unit area or a change in elevation. Visual evidence of tillage erosion includes: loss of organic rich topsoil and exposure of subsoil at the summit of ridges and knolls (Fig. 3), and undercutting of field boundaries (fencelines, hedgerows, terraces, etc.) on the down-slope side and burial on the up-slope side.

Figure 2. Simple illustration of tillage erosion. a) Variability of translocation in hilly landscape (upslope-downslope tillage) - soil loss occurs on convex areas and accumulation occurs on concave areas. b) Variability of translocation in landscapes with simple, dissected slopes (contour tillage, grassed water diversion terraces) - soil loss occurs on uppermost portion of slope segments and accumulation occurs in lower portions. Translocation indicated by arrows.

Figure 3. A landscape that is severely eroded by tillage erosion, near Fergus Falls, Minnesota, 1999. In the foreground, note the calcareous subsoil tilled to the surface where it will be incorporated into the till-layer.