TEP: A Tillage Erosion Prediction model to calculate soil translocation rates from tillage

Soil movement by tillage is a function of slope gradient. Tillage direction performed upslope and downslope in opposing directions over alternate year s results in a net downslope movement of soil. The objective of this study was to develop a simulation model to describe soil redistribution along a h illslope transect that ran be used to explain observed erosion and depositi on patterns in cultivated fields that result from tillage action. A diffusi on-based conceptual model was used to represent soil redistribution by till age, whereby the regression coefficient for the relationship between transl ocation and slope gradient was described by a diffusion coefficient, k'. So il redistribution was calculated over a 50-yr period on a measured topograp hic transect in west central Minnesota using published k' values for the mo ldboard plow. Additional simulations included the additive effects of secon dary tillage (tandem disc) and an examination of hillslope segment lengths on soil redistribution rates. Results showed that 14.7% of the area from th e measured transect would experience a loss or gain in sail that exceed 10 t ha(-1) yr(-1) with moldboard plow using a k' value of 2.34 kg m(-1) slope width. The loss or gain in soil that exceed 10 t ha(-1) yr(-1) increased t o 26% of the area with a k' value of 3.30 kg m(-1). The addition of seconda ry tillage (two tandem disc operations) increased the area of excessive soi l redistribution to 59%. The Tillage Erosion Prediction (TEP) model has the capability to identify areas based on landscape configuration of excessive soil loss (erosion) or gain (deposition) due to soil ti translocation by t illage.