ИСТИНА

The findings are presented of a detailed study about the long term (75-80 years) effectiveness of soil conservation measures, which was conducted at the Novosil study site located in the Orel region of the Central Russian Plain. At the Novosil Experimental station, two pairs of transects of different morphology were selected on relatively steep arable farmland. One transect in each pair underwent introduction of soil conservation measures in the past, while the other was kept under traditional cultivation. On both transects under soil conservation practices artificial terraces were installed in combination with forest belts located parallel to the topography contour lines and spaced at approximately 100 m from each other. The construction of terraces and tree planting was initiated in 1932. Simultaneously radionuclide technique, soil profile morphology method and empirically based erosion modelling were used for quantitative assessment of long term soil conservation effectiveness within each pair of transects. The results, based on soil profile morphology and 137Cs based methods, concluded that slopes with soil-protective measures are characterized by a reduction of the average annual soil redistribution rates by 25-80%. High coincidence of the spatial patterns of soil redistribution rates provided by these two techniques suggests general reliability of the results. Observed discrepancies in values obtained can be attributed to differences in temporal resolution of methods as well as to possible influence of individual extreme events on results yielded by the 137Cs method. More significant decrease of average soil degradation rates on slopes under soil conservation practices (up to 70-75% for each pair of slopes) was predicted by empirically based modelling. This substantial differences between predicted and directly measured values is attributed to a high degree of soil degradation prior to the introduction of protective measures (reflected by the soil-morphological method).