Assessment of USLE cover-management C-factors for 40 crop rotation systems on arable farms in the Kemmelbeek watershed, Belgium

In order to calculate the actual erosion according to the universal soil loss equation (USLE) and to estimate the impact of land use on soil erosion it is important to know the C-factor. Based on the USLE crop-growth stages, the cover-management C-factors were calculated for the main crop rotation systems on arable farms in Belgium with particular reference to those occurring on 40 farms on silt and silt loam soils in the Kemmelbeek watershed, West-Flanders, Belgium. The different rotation systems were composed of the following crops: sugar beet (SB), winter wheat (WW), potato (PO), maize (M), beans (B), winter barley (WB), peas (PE), chicory (CH), leek (L), carrot (CA), celeriac (CE), rye grass (RG) and temporal grassland (TG). The erosivity factor R during the rotation was calculated on the basis of a detailed rainfall time series over a time period of 27 years. The crop data (development of cover, sowing and harvesting date, amount of residue) were collected from literature and personal communications. For most rotation systems the C-factors were between 0.28 and 0.38. High C-factor values were obtained with M/M/M/PO (C=0.47), and with CE/L/PO (C=0.51). Remarkable small C-values (C=0.24–0.27) were found when winter cereals (WW and WB) were put in the rotation scheme. Whether or not the foliage of the sugar beets was removed, had no effect on the C-factor. The effect of green manuring on the C-factor in some rotation schemes was smaller than could be expected. The C-factor was also affected by the position of the crop in the rotation scheme. The calculated C-factors indicated that the application of some rotation systems might cause more erosion by runoff. Therefore, these calculated C-factors can be used as a criterion to select an appropriate rotation system to reduce erosion risk on site. However, validation of these values using experimental field plot data is still required.