INTEGRATED ASSESSMENT AND ANALYSIS OF PHYSICAL LANDSCAPE PROCESSES THAT IMPACT THE QUALITY AND MANAGEMENT OF AGRICULTURAL WATERSHEDS
Location: Watershed Physical Processes Research Unit
Title: Modeling edge effects of tillage erosion
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 8, 2010
Publication Date: December 28, 2010
Citation: Vieira, D.A., Dabney, S.M. 2010. Modeling edge effects of tillage erosion. Soil & Tillage Research. 111(2):197-207.
Interpretive Summary: Tillage operations move soil downhill, causing erosion of uppermost areas of hillslopes, and soil accumulation near hill bottoms. When tillage is performed in narrow contour strips, the process is intensified because soil is slowed plowed away from the top of each strip, exposing subsoil, while it accumulates at the bottom of each strip. Tillage erosion also redistributes chemicals and nutrients that are important to plant growth, causing increased variability of soil properties, which affects soil productivity and reduces crop yields.
A computer model has been developed to predict erosion caused by tillage. For a given field topography and a record of tillage operations, the model computes where erosion and soil accumulation take place, and how the erosion process evolves through the years. The model has been applied to predict such changes in a test field near Coffeeville, MS, where contour tillage has been performed between grass hedges for many years. The site was chosen because detailed land surveys and tillage records were available, providing the opportunity to verify the performance of the model. The model was used to predict tillage erosion over a 12-year period. Simulation results matched well the patterns of soil erosion and accumulation observed in the field.
Model applications to field sites where high-quality data are available serve to verify that the model correctly simulates the physical processes that occur in nature. More importantly, success in reproducing what has been observed in actual fields validates the use of the model as a predictive tool. Simulations conducted with the new model can be used to identify problem areas within a field, evaluate the performance of alternative practices, and ultimately prescribe remedial measures that will help maintain crop productivity.
Erosion caused by tillage has been recognized as an important factor on soil redistribution and on the development of soil loss and accumulation patterns. The presence of field borders, fences, and vegetated strips creates discontinuities in the soil flux that lead to increased local erosion or accumulation. Repeated tillage operations decrease the terrain slope steepness in the vicinity of these barriers, and accelerate the formation of terrace benches and the creation of lynchets where the soil movement is interrupted.
The two-dimensional Tillage Erosion and Landscape Evolution Model has been applied to an experimental field in Coffeeville, Mississippi, where grass hedges were planted close to field elevation contours to evaluate their effectiveness as an erosion control measure, and to investigate the formation of landscape benching. The model correctly reproduced the location and magnitude of soil loss and accumulation over a 12-year period. Soil redistribution due to tillage is comparable to field observations that showed erosion averaging 20 cm occurred in the downslope side of each vegetative strip and deposition taking place upslope of them. The net result was a reduction from 7% to 5% in the average grade of the tilled areas between the hedges.