Experience with the assessment of the USLE cover-management factor for arable land compared with long-term measured soil loss in the Swiss Plateau
Volker Prasuhn
Abstract
The cover-management factor (C-factor) of the Universal Soil Loss Equation (USLE) is the most important factor for estimating the effects of farming practices or agricultural policy measures on soil loss rates. This study, conducted in Switzerland from 1987 to 2017, assessed the impact of mitigation measures on arable land by comparing modelled C-factor values and measured soil losses. C-factor values were calculated in detail for 203 fields for five different periods (1987–89, 1997–99, 1997–2006, 2003–09, 2010–14) using a C-factor tool adapted to Swiss conditions. The C-factor values were compared with the measured soil loss rates of the same fields from the three periods 1987–89, 1997/98–2006/07, and 2007/08–2016/17. Given various action programmes, the share of conservation tillage practices increased from 4% in 1997/98 to 85% in 2014/15. The mean annual soil loss was 0.71 t ha–1 yr–1 (1987–89) and decreased by over two-thirds from 0.74 t ha–1 yr–1 (1997/98–2006/07) to 0.20 t ha–1 yr–1 (2007/08–2016/17), while the mean C-factor values were 0.136 in 1987–89 and decreased by almost half from 0.094 (1997–99) to 0.050 (2010–14). This study demonstrates that, with an in-depth calculation of C-factor values over different periods, changes amounting to soil loss resulting from the implementation of mitigation measures can be satisfactorily reproduced for a region.