Effects of Contour Plowing by Rotary Cultivator on Vertical Redistribution of Soil Organic Carbon

Abstract

Simulated tillage and magnetic tracing techniques were applied to study the effects of contour plowing by rotary cultivator on vertical migration of soil organic carbon (SOC) on a steep hillslope in purple soil, revealing the relationship between SOC vertical and downslope movements. Contour plowing by rotary cultivator played an important role on downslope transfers of the soil, resulting in an obvious transformation of soil profiles with tillage depth at the summit position. The depth distribution of soil magnetic susceptibility showed that tillage brought about the vertical downward migration of the soil magnetic tracer. The intense tillage led to the vertically downward transfer of SOC, but vertical redistribution patterns differed from one another at different slope positions. Due to upward migration of parent rock debris and downslope transport of soil, SOC concentrations in the surface soil layer (0-10 cm) was reduced significantly at the summit position. For the backslope and footslope positions, SOC concentrations at 0-20 cm was reduced remarkably due to mixture effects of tillage and tillage erosion. SOC in the surface layer (0-5 cm) was decreased slightly at the toeslope position, but that at 5-20 cm increased significantly. This study indicated that the vertical movement of soil interacted with the downslope movement, which resulted in significant variation of SOC from the summit to toeslope positions.