Assessment of gravelly soil redistribution caused by a two-tooth harrow in mountainous landscapes of the Yunnan-Guizhou Plateau, China

- High rock fragment contents of soils lead to an introduction of the two-tooth harrow.
- The angle of response for gravelly soils was approximately 0.69-0.70 m m−1.
- Tillage transport coefficients of gravelly soils were smaller than the muddy soils.
- Large-size rocks played a significant role in diminishing tillage depth.
- Small contact area between the harrow and soils leads to a small displacement.

The processes of soil redistribution caused by hoeing tillage in hilly areas have been increasingly recognized for nearly two decades. Yet, few studies have examined the effects of hoeing tillage on soil redistribution in rocky mountainous areas. Due to a high rock fragments content of gravelly soils, a special type of hoe called the two-tooth harrow has been widely used in the Yunnan-Guizhou Plateau, China. In order to assess gravelly soil redistribution, a series of tillage experiments were set up and the subsequent data were compared with those acquired previously in hilly areas. The displacement distance of gravelly soils increased with slope gradient linearly in the range of 0.05 to 0.69 m m−1; however, when the slope gradient extended further, an exponential equation could better describe the relationship between them. The repose angle of gravelly soils was approximately 0.69-0.70 m m−1. Large-size rock contents and implement types are two important factors affecting tillage depth. Tillage transport coefficients (k3 and k4) of gravelly soil in rocky mountainous areas were 40 and 78 kg m−1 tillage pass−1, respectively, displaying a slightly large k3 value but a significantly small k4 value compared with those in hilly areas. Due to its energy saving and applicability to gravelly soils, the two-tooth harrow is more attractive to farmers than the normal hoe in rocky mountainous areas. Moreover, the two-tooth harrow is proved to be efficient and effective in reducing tillage erosion than the normal hoe.