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

Abstract

Field observations in central Belgium indicate a significant soil degradation process which has hitherto not been considered in assessments of soil erosion rates: i.e., soil losses due to root crop harvesting (SLRH). The objectives of this study were: (1) to assess SLRH for two commonly grown root crops 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 soil degradation process to overall soil loss in the study area. Soil losses due to harvesting of witloof chicory roots were assessed by measuring dirt tare from 43 root samples whereas SLRH for inuline chicory roots and sugar beet were calculated from dirt tare data provided by factories processing these roots. Mean soil loss was 11.8 ton 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. Assuming that root crops are grown once in 2 years in the study area, mean annual SLRH equals 5.0 ton ha −1 year −1 (0.33 mm/year). Since these root crops have been grown over a period of at least 200 years in Belgium, this implies a mean soil profile truncation of 66 mm. However, important spatial and temporal variability in SLRH data was observed, depending on soil texture, soil moisture at harvest time and harvesting technique. Given the importance of SLRH, it needs to be incorporated into future assessments of soil degradation processes and sediment budgets.