Sediment generated by interrill erosion is commonly assumed to be enriched in
soil organic carbon (SOC) compared to the source soil. However, the reported SOC
enrichment ratios (ERSOC) vary widely. It is also noteworthy that most studies reported that
the ERSOC is greater than unity, while conservation of mass dictates that the ERSOC of
sediment must be balanced over time by a decline of SOC in the source area material.
Although the effects of crusting on SOC erosion have been recognized, a systematic study on
complete crust formation and interrill SOC erosion has not been conducted so far. The aim of
this study was to analyze the effect of prolonged crust formation and its variability on the
ERSOC of sediment. Two silty loams were simultaneously exposed to a rainfall simulation for
6 h. The ERSOC in sediment from both soils increased at first, peaked around the point when
steady-state runoff was achieved and declined afterwards. The results show that crusting
plays a crucial role in the ERSOC development over time and, in particular, that the
conservation of mass applies to the ERSOC of sediment as a consequence of crusting. A
“constant” ERSOC of sediment is therefore possibly biased, leading to an overestimation of
SOC erosion. The results illustrate that the potential off-site effects of selective interrill
erosion require considering the crusting effects on sediment properties in the specific
context of the interaction between soil management, rainfall and erosion.