Pattern of cumulative soil erosion and redistribution pinpointed through magnetic signature of Chernozem soils

Abstract

An experimental approach for estimation of cumulative soil erosion by using magnetism of Chernozem soils is presented. An agricultural land of 4.5ha, utilized for crop production, has been mapped at 10×10m grid interval by using magnetic methods. Field measurements of magnetic susceptibility show high sensitivity to the present soil surface conditions (crop residue cover, soil compaction, sealing) in addition to the main response to erosional removal of the uppermost soil horizons. Laboratory measurements of magnetic susceptibility (χ), frequency dependent magnetic susceptibility (χfd) and Isothermal Remanent Magnetization on soil samples allow construction of surface maps of these magnetic characteristics. Their systematic depth variations along non-disturbed reference soil profiles have been established, which lead to the construction of empirical predictive curves of cumulative soil loss according to the model, proposed by Royall (2001). Using the predictive curves of χ and χfd, maps of soil magnetic parameters are transformed into the distributed pattern of predicted soil loss. Comparison of the maps with terrain slope reveals that in the upper slope positions (having slopes of 1–5°) tillage redistribution plays the main role. In contrast, at toe slope sites, characterized by higher slopes (11–15°), water erosion caused significant removal of soil material. Mean annual erosion rates of 8–6.8t/ha/y have been calculated, which corresponds to about 50years of agricultural land use.