TILLAGE TRANSLOCATION AND TILLAGE EROSION ON SHOULDER SLOPE LANDSCAPEPOSITIONS MEASURED USING CS-137 AS A TRACER

Tillage erosion, the net downslope translocation of soil by tillage, w as measured on eight shoulder slope landscape positions within two fie lds in the upland regions of southwestern Ontario. Translocation of so il by tillage was measured by labelling plots of soil with Cs-137 and measuring its displacement in response to tillage. Paired plots were u tilized to compare soil translocation by upslope and downslope tillage . A single sequence of conventional tillage operations, consisting of mouldboard plough, tandem disc (double pass) and C-tine cultivator, tr anslocated 90 kg soil m(-1) slope width when tillage was conducted ups lope, and 142 kg m(-1) when conducted downslope. Net downslope translo cation resulting from one upslope tillage sequence and one downslope, was 52 kg m(-1). Assuming one sequence of tillage operations occurs pe r year and is conducted upslope and downslope equally often, the rate of net downslope translocation would be 26 kg m(-1) yr(-1). The source area from which this soil loss occurred was defined by an average slo pe length of 5.2 m between paired plots and hillslope summit. The esti mated rate of soil loss from this area was in excess of 5.4 kg m(-1) y r(-1) (54 t ha(-1) yr(-1)). Tillage erosion accounted for at least 70% of the total soil loss from natural and tillage erosion as estimated by resident Cs-137.