Wednesday, November 7, 2007 - 10:15 AM
303-4

Modeling Tillage-induced Redistribution of Soil Mass and its Constituents within Different Landscapes.

Sheng Li1, David Lobb1, Michael Lindstrom2, Sharon Papiernik3, and Annemieke Farenhorst4. (1) University of Manitoba, Department of Soil Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada, (2) USDA-ARS, USDA ARS-NC Soil Consv Res Lab, 803 Iowa Ave., Morris, MN 56267, (3) USDA-ARS-NPA-SPNRU, USDA-ARS, 803 Iowa Avenue, Morris, MN 56267, (4) 380 Ellis Bldg., University of Manitoba, University of Manitoba, Dept. of Soil Science, Winnipeg, MB R3T 2N2, CANADA

Tillage is a driving force of soil movement in cultivated fields. Soil constituents, together with the mass of soil, are redistributed over landscapes by tillage. The pattern of tillage-induced soil constituent redistribution is not only determined by the pattern of tillage-induced soil mass redistribution but also by the extent of translocation and by transfers between the till-layer and the subsoil layer. In this study, we used a convoluting procedure and developed a model (TillTM) to simulate the tillage translocation process and 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 and over different temporal scales. The model was validated against field data collected at a site near Cyrus, Minnesota, USA. We determined that local-tillage-erosion rate is mainly dependent on topography and that the effects of tillage pattern and temporal scale on tillage erosion 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 on these positions. Net loss of OC content occurs in the till-layer and this loss increases over time in all four hypothetical landscapes. In contrast, increase of OC content in the sub-layer occurs at soil accumulation positions. The application of the TillTM on the Cyrus site demonstrated that using the model, the pattern of OC and inorganic carbon (IC) redistribution over time can be adequately estimated.