Soil losses due to harvesting of chicory roots and sugar beet: an underrated geomorphic process?

Field observations in central Belgium indicate a significant soil degradati on process which has hitherto not been considered in assessments of soil er osion rates: i.e., soil losses due to root crop harvesting (SLRH). The obje ctives of this study were: (1) to assess SLRH for two commonly grown root c rops in Belgium, i.e. chicory roots and sugar beet, (2) to investigate some factors controlling the spatial and temporal variation of SLRH, and (3) to evaluate the contribution of this sail degradation process to overall soil loss in the study area. Soil losses due to harvesting of witloof chicory r oots were assessed by measuring dirt tare from 43 root samples whereas SLRH for inuline chicory roots and sugar beet were calculated from dirt tare da ta provided by factories processing these roots. Mean soil loss was 11.8 to n ha(-1) harvest(-1) for witloof chicory roots, 8.1 ton ha(-1) harvest(-1) for inuline chicory roots and 9.1 ton ha(-1) harvest(-1) for sugar beet. As suming that root crops are grown once in 2 years in the study area, mean an nual SLRH equals 5.0 ton ha(-1) year(-1) (0.33 mm/year). Since these root c rops have been grown over a period of at least 200 years in Belgium, this i mplies a mean sail profile truncation of 66 mm. However, important spatial and temporal variability in SLRH data was observed, depending on soil textu re, soil moisture at harvest time and harvesting technique. Given the impor tance of SLRH, it needs to be incorporated into future assessments of soil degradation processes and sediment budgets. (C) 2001 Elsevier Science B.V. All rights reserved.