Steady-state models for the movement of soil and straw during tillage with a single sweep

A concept of steady-state movement, which mathematically describes the amount of soil and straw moving by a sweep, is proposed. A sweep model for the steady-state movement of soil and straw in front of a sweep was developed and validated by an experiment conducted in an indoor soil bin using three different lengths of oat straw and a 325 mm wide sweep. Existing soil-cutting models were also applied to the development of steady-state models. A three-dimensional model based on an earlier model model was developed for narrow tools; and a two-dimensional model originally proposed for earthmoving machines was developed for wide tools. The results of a validation exercise indicated that these steady-state models would predict the amount of soil and straw moving during tillage with a sweep even though the sweep was a wide tool at the tillage depth of 100 mm. However, the three-dimensional model and the two-dimensional model highly overestimated the amount of straw moving by a sweep. A possible reason was that the three-dimensional model was based on a model that was developed for a narrow blade but not a sweep. The sweep model proposed in this study provided the best results among these three models considering predicting both soil and straw moving zones. The relative error of the sweep model was 22% or less when predicting the amount of soil moving, and less than 12% when predicting the amount of straw moving. Application of existing soil-cutting models to the steady-state movement of soil and straw needs further study.