Soil tillage and scale effects on erosion from fields to catchment in a Mediterranean vineyard area

Soil erosion surveys and modeling approaches often rely on datasets collected from small experimental plots or fields. Therefore, one important issue is to assess to what extent reference data collected on small areas can be affected by soil tillage practices and extrapolated to larger areas. The objectives of this paper are to discuss: (i) the impact of superficial tillage on the erosion rates at field scale and (ii) the impact of the scale on the erosion rates for areas ranging from small fields to 1 km2 catchments. We analyzed a dataset of 18 rainfall events including runoff and erosion data from fields of approximately 1200 m2 and 3200 m2 consisting of vineyards with two contrasting weeding practices – either superficial tillage or no-tillage with chemical weeding – and from the outlet of a 0.91 km2 catchment that was 70% vineyard. Results showed that superficial tillage significantly reduced (4.5 times) soil losses as compared to no-tillage, with a large event-to-event variability. Considering the natural conditions studied by the authors, no-tillage with chemical weeding is not recommended for the study area. Erosion rates observed at catchment scale were significantly lower than those observed at the scale of individual fields. This trend, which has already been observed by many researchers, confirms that catchment soil loss cannot be estimated by the sum of individual field soil losses. In this context, the scaling transition between the field and the 1 km2 catchment can be analyzed in terms of the spatial variability of soil management and connectivity between the sediment-producing and deposition areas.