Tillage erosion and its effect on spatial variations of soil organic carbon in the black soil region of China

The black soil region of Northeast China is characterized by flat to gentle undulating topography; it is ideally suitable for tillage with machines and has become the forefront for the expansion of agricultural mechanization in China. As a result, the potential risk of soil erosion has been inevitably increased with the increases of tractor power, tillage speed, and depth. Tillage erosion, however, has been overlooked as a significant form of soil erosion in this area. Thus, this study aims to 1) provide direct measurements of tillage translocation due to moldboard plowing; and 2) analyze the effect of tillage erosion on the spatial variation of soil organic carbon (SOC). Tillage translocation was determined in a plot experiment using stone chips as tracers. After a single tillage pass, traced soils were translocated 0.095-0.342 m at 32.7-134.1 kg m(-1), with more soil materials translocated in the downslope tillage than in the upslope tillage. The tillage erosivity, expressed in terms of tillage transport coefficient, was 234 kg m(-1) tillage pass(-1). An established Directional Tillage Erosion Model (DirTillEM) was used to predict tillage erosion on the experimental field. High soil loss occurred in the top and lower section of slope, whereas the middle- and bottom section areas reflected soil accumulation. The spatial pattern of SOC exhibited an approximately opposite trend as tillage erosion in the study field, and SOC concentrations were negatively correlated with tillage erosion rates, indicating that tillage erosion likely has contributed to SOC redistribution. The findings suggest that tillage erosion could be a major cause of soil redistribution on sloping farmland in the black soil region of Northeast China; thus, more attention should be given to tillage erosion for its impacts on soil quality and C dynamics in the black soil region.