An interaction between vertical and lateral movements of soil constituents by tillage in a steep-slope landscape

- The lateral transfer of soil constituents proceeded in the same direction as the soil movement by tillage.
- The vertical transfer patterns differed from one another for the upper, middle, and lower slope positions.
- SOC/TN changes of the surface soil affected the underlying soil due to the vertical transfer.
- The vertical movement of soil constituents interacted with their downslope movement under tillage.

The interaction between vertical and lateral movements of soil constituents by tillage needs to be addressed to better understand the transfer processes of soil constituents on a hillslope. In this experiment, traditional tillage by consecutive hoeing during a few days and the cesium-137 (137Cs) tracing were performed in the Sichuan Basin, China to demonstrate direct effects of intensive tillage on the vertical redistribution of soil constituents and the interaction between vertical and lateral transfers of soil constituents. The changes in 137Cs residual rates showed that intensive downslope movement of soil by tillage occurred along the transect of slopes, and the lateral transfer of those soil constituents proceeded in the same direction as the soil movement by tillage. The vertical transfer patterns differed from one another for the upper, middle, and lower slope positions. At the upper slope positions, intensive tillage notably decreased the concentrations of soil organic carbon (SOC) and total nitrogen (TN) in the whole soil profile. At the middle and lower slope positions, SOC concentrations in the surface soil layer (0-15 cm) markedly declined after intensive tillage, suggesting that the downslope movement of soil by tillage translocated the soil with low concentrations of SOC and TN derived from upslope towards the middle and lower slopes. The decreases in SOC and TN of the surface soil exerted an important impact on the underlying soil near the surface soil due to the vertical transfer of soil constituents by mixture effects of tillage. Significant changes in the depth distribution pattern of soil constituents by intensive tillage occurred close to the upslope and downslope boundaries of the field Our results revealed that the vertical movement of soil constituents interacted with their downslope movement under intensive tillage, which resulted in a chain transfer process of soil constituents: effects of the vertical transfer at all landscape positions on the lateral transfer along the transect of slopes, and conversely, effects of the lateral transfer on the vertical transfer.