Modeling Edge Effects of Tillage Erosion

Authors: Vieira, Dalmo; Dabney, Seth

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2010
Publication Date: 1/1/2011
Citation: Vieira, D.A., Dabney, S.M. 2011. Modeling edge effects of tillage erosion. Soil & Tillage Research. 111(2):197-207.

Interpretive Summary: Tillage operations can move a significant amount of soil, can cause significant erosion of sloping cropland, and can cause the formation of small berms or terraces at downslope field boundaries that may alter runoff water flow paths. Tillage berms may affect the performance of soil conservation practices: their presence can be detrimental, when for example runoff is prevented from entering grass buffers or waterways, or beneficial and desirable, when runoff water is safely diverted to a stable outlet. We developed a computer model to predict erosion caused by tillage and to predict the development of tillage berms. We compared predictions with field observations at two sites in northern Mississippi. Agreement between predictions and observations verified that the model correctly reproduces the locations and magnitude of soil loss and accumulation, and the formation of tillage berms that may significantly affect field scale hydrological and water erosion processes. Simulations conducted with the new model can be used to help design systems of conservation practices and to evaluate their long-term term effects on soil erosion.

Technical Abstract: Tillage erosion has been recognized as an important factor in redistribution of soil over time and in the development of morphological changes within agricultural fields. Field borders, fences, and vegetated strips that interrupt soil fluxes lead to the creation topographic discontinuities or lynchets. When tillage tools that preferentially throw soil to one side are used repeatedly to move soil in one direction, rather than alternating with each pass, they create berms at the receiving side of the tilled domain and a “dead furrow” or channel at the contributing side. However, even tillage implements that are symmetrical in throwing soil equally in both lateral directions on flat surfaces may throw some soil beyond the implement width and so contribute to soil berms formation just beyond the tilled zone that can affect water flow paths. We developed a two-dimensional Tillage Erosion and Landscape Evolution Model that allows complex internal boundaries to be defined within the simulation domain. In this paper we develop and demonstrate techniques and tools to allow prediction of the formation of edge-of-field berms by defining alternative boundary conditions. The derivation and assumptions of the model are presented and then it is applied and compared to survey results from two field studies: one 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 were monitored over a 16-year period; and the other a set of 0.1 ha plots located near Holly Springs, MS where the effect of edge-of-field berm formation on runoff partitioning was evaluated during an 8-year study. Results demonstrate the ability of the model to correctly reproduce the location and magnitude of soil loss and accumulation and demonstrate development of berms that may significantly alter field-scale hydrological, erosion, and sediment transport processes.