Tillage erosion as an underestimated driver of carbon dynamics

Abstract

Arable soils may play an important role in climate mitigation actions as soil management directly affects carbon (C) sequestration and mineralisation. To evaluate the C sequestration potential in hilly terrain it is essential that not only changes in vertical C fluxes (more C input and/or reduced mineralisation), but also lateral soil organic carbon (SOC) redistribution due to erosion processes are considered. Tillage has been identified as an important contributor to soil translocation processes and a modulator of SOC dynamics. Nevertheless, the focus of most studies dealing with SOC redistribution still lies on water erosion. Therefore, the aim of this study is to assess the impact of tillage erosion on C fluxes in the intensively cultivated loess region (200 ha) in the Czech Republic. The coupled water and tillage erosion and C turnover model SPEROS-C was used to analyse the effect of six decades of erosion/deposition upon C fluxes, whereas a specific focus was set on the importance of tillage erosion processes. The results indicate that tillage erosion (TIL) is an important driver of C dynamics in the study area, especially at slope shoulders where a substantial decline in SOC was modelled. Water erosion (WAT) is the most dominant process in the region. However, the model results reveal an increase in erosion-induced C sequestration potential by 37 % after 60 years of simulation when effect of TIL is considered. Moreover, it is interesting that TIL reduced the total sediment delivery from the monitoring site via a change in topsoil SOC patterns. In other words, tillage lowered water erosion-induced sediment transport. Overall, considering the overlooked impact of tillage erosion led to a substantial shift in the role of soil erosion on SOC dynamics. The climate mitigation measures based on adapted agricultural management to increase SOC sequestration are often in-line with soil conservation measures. Our results indicate that such an adaptation might be less effective as the erosion-induced C sink effect declines.