Quantitative Assessment of Soil Erosion by Magnetic Tracer Method At Sites within Russia and USA.

Appearance of spherical magnetic particles (SMPs) in soils is mainly connected with atmospheric deposition, resulting from coal burning by locomotives, so period of active SMP emission is the last 130-150 years. The quantitative assessment of the rate of soil erosion was based on a comparison of the concentrations of spherical magnetic particles (SMPs) in soils on different parts of slopes relative to their concentrations on flat summits. Rate of soil erosion in relation to the character of land use on slopes has been obtained for Belgorod and Moscow sites in Russia (the steppe zone and forest zones) and the Springfield and Hanover sites in Illinois, USA. Under natural vegetation (woodland and grassland; alfisols and mollisols) erosion loss either absent or very low (less than 1-2 t/ha per year). The rate of soil erosion on similar cultivated slopes increased significantly – up to 15-25 t/ha per year or more. At all the investigated sites, soil erosion on the south facing slopes was higher than that on the north facing slopes. The difference between the rates of soil erosion on the slopes of southern and northern aspects for relatively steep (5° and 6°) surfaces was from 2.5 to 6 times. For gentle (up to 3°) slopes it decreased to 1.4 times. On the convex and linear slopes, the zones of erosion and deposition of the soil material alternated with one another along the entire slope. The analysis of their localization did not show any definite correlation of these zones with the particular parts of the slopes. On the complex convex–concave slopes, the alternation of the zones of erosion and deposition of the soil material was observed within the upper (convex) parts of these slopes. Within the lower (concave) parts of the slopes, the processes of erosion predominated at all the studied plots.