Effects of soil conservation practices on soil losses from slope farmland in northeastern China using runoff plot data

Various conservation practices have been used to control soil erosion in cropland which makes assessing the effects of soil conservation more important. Northeastern China is an important crop-producing regions, with severe soil erosion. In the study, 110 runoff plot-year observations from seven experimental stations distributed over the region were used to assess the effects of local conservation practices on soil erosion, using a simplified USLE. Under the assumption that there were no significant differences in rainfall erosivity and soil erodibility in the study area under the "no practice scenario", we described a simplified linear model based slope steepness and soil loss rate. The Jixing watershed was selected as a case study to test the model. The results indicate that the derived model can be used in the NE region of China for conservation assessment. The P factor values, related to main soil conservation practices, were derived from the observed plot-year data. The average values of P factor were around 0.01 to 0.35, which were low enough to justify their conservation effects of implementation through the assessment Comparing to the conventional slope ridging tillage, the conservation rates of terraces, strip ridging, orchards and agro-forestry in the Jixing Watershed were 0.57, 0.6, 1.07, and 0.62 mm/ha, respectively, obtained by the assessment method in the study case. The paper neglected the seasonal variation which should be grouped to the C factor for the annual data and discussed the limitations of the assessment model for application.