Trace element concentration data for tracing soil erosion at the plot-scale under different tillage methods

Several tracing methods have been developed and applied to characterize the spatial distribution of runoff sediment within agricultural plots. In this study, we evaluated whether natural concentrations of refractory and rare earth elements (REEs) in soils and runoff sediments can be used for erosion tracing under conventional ploughing and conservation reduced tillage. Several elements (Ba, Cs, Ga, Nb, Rb, Sr, La, and Tb) showed a significant downslope increase in soil concentrations in both plots, whereas Hf and Zr exhibited a downslope decrease. Comparison between soils and runoff sediments allowed the distinction among enriched (Ba, Co, Cs, Ga, Rb, Sr, Th, V, and Eu), moderately enriched or non-enriched (Nb, Ta, U, Y, and REEs), and depleted (Hf and Zr) elements. The magnitude of enrichment and depletion differed significantly between the two plots. Although elemental ratios did not differ significantly between soils and sediments, they exhibited substantially higher variability in the sediments. Ratios of Ba, Cs, and Rb to Hf and Zr generally increased significantly downslope. These results demonstrate that downslope sediment transport can be detected using natural trace element concentrations in a geochemically homogeneous area under different tillage practices. Elemental ratios combining elements with contrasting geochemical behavior are particularly effective, provided they are associated with phases that respond differently to erosion. The Ba/Zr ratio proved especially suitable for tracing erosion in loess soils.