Modeling Translocation and Dispersion of Soil Constituents by Tillage on Sloping Land

Recent studies clearly indicated that soil tillage is a major factor affecting soil redistribution on arable land. However, existing modeling studies of the redistribution of soil constituents by tillage are largely theoretical in nature due to the lack of sufficient experimental data. This paper describes the results of field experiments carried out with a moldboard plow on different slope gradients showing that an important net downslope translocation and dispersion of soil constituents is associated with soil tillage. Both translocation and dispersion are strongly affected by slope gradient. Available experimental evidence suggests that redistribution of soil constituents can be modeled by convoluting the displacement probability distribution with the spatial distribution of the soil constituent. The convolution model presented here was found to be superior to existing models because it accounts for dispersion, directionality of tillage, and topography. A comparison of soil property data with model simulations indicated that soil tillage is a major factor when assessing the effect of erosion processes on the variability of soil properties.