Modeling Tillage-Induced Redistribution of Soil Mass and Its Constituents within Different Landscapes

Tillage is a driving force of soil movement in cultivated fields. Soil constituents, together with the mass of soil, are redistributed across landscapes by tillage. The pattern of tillage-induced soil constituent redistribution is determined by the pattern of tillage erosion (tillage-induced soil mass loss or gain) and the dispersivity of translocation. In this study, we used a convoluting procedure and developed a Tillage Translocation Model (TillTM) to simulate the tillage translocation process and to demonstrate tillage-induced soil mass and soil organic carbon (OC) (as an example of soil constituents) redistributions across four hypothetical landscapes subjected to different tillage patterns (directions) and over different lengths of tillage period. We determined that the local tillage-erosion rate is mainly dependent on topography and that the effects of tillage pattern and the length of tillage period are relatively minor. The redistribution of OC content in the till layer is mainly determined by the number, location, and size of soil loss positions in the landscape, as well as the soil loss rates at these positions. Net loss of OC content occurs in the till layer and this loss increases with time. In contrast, an increase of OC content in the sublayer occurs at soil accumulation positions. The model was validated against field data collected at a site near Cyrus, MN. The patterns of OC and inorganic C redistribution can be adequately estimated by TillTM. There are discrepancies, however, between the model-estimated values and the field measurements due to the limitations and uncertainties associated with the model. The results clearly showed that tillage translocation causes the vertical redistribution of soil constituents across the landscape, which implies that tillage translocation is one of the driving forces behind the spatial variability of soil properties and properties that impact biophysical processes.