Results of 10-years runoff plot experiments carried out on two sites of the Lublin Upland were presented. Despite similar soils and climatic conditions, studies showed large differences in annual soil erodibility (K factor of the USLE) between both sites. Experimentally derived values of the factor were dependent on tillage direction and time of maintaining runoff-plots in fallow conditions. On a site cultivated in contour direction, 4-year period was insufficient to achieve K values similar to the predicted values from the USLE. In contrast to this, on a site cultivated up-down slope, similar experimental and predicted K values were obtained after 2 years and remained at the same level during next 4 years. Results enabled to identify limitations of the USLE application for erosion prediction in Poland. Studies proved that soil erodibility could be used for prediction of erosion risk for silt loam developed from loess. However, application of soil erodibility approach to the event–base models is questionable for variation of K factor in the initial years. As far, the factors affecting soil erodibility changes are not recognized and need further research.
Poland remains one of the few countries with nationwide assessment of erosion risk in detailed scales. An existing map of potential water erosion risk was produced in 1980 according to the qualitative method of potential water erosion risk (PWER) indicator, developed by Anna and Czeslaw Jozefaciuk. The potential erosion risk indicator means an erosion thread for the soil without any plant cover and based on only relatively static factors of slope, soil kind (texture) and average annual rainfall, distinguishing five grades of erosion intensity. The indicator provides no information for real and actual state of erosion risk, which depends mostly on the kind of land use. Therefore, an effort has been made to produce a map of actual water erosion risk for Poland, based on the Józefaciuks' methodology for the qualitative indicator of actual water erosion risk (AWER), which includes a land use factor as well as a factor for erosion prevention techniques. The work includes the production of an actual water erosion map based on the digitized map of potential water erosion at a scale of 1:300,000 and CORINE Land Cover 2000 as a source for land use information. The results show relatively high actual erosion risk in highest intensities: 1.7% of Poland under very strong erosion, 1.0% under strong erosion and 4.4% under average erosion. Compared to potential water erosion, where the same grades cover 17.6% of the country's area, the erosion risk at high grades decreased by 10.5%. According to the land use structure derived from CLC2000, around 2,300,000 hectares show the risk of water erosion in high erosion intensity grades and require erosion control measures.