EFFECTS OF FIELD REORGANISATION ON THE SPATIAL VARIABILITY OF RUNOFF AND EROSION RATES IN VINEYARDS OF NORTHEASTERN SPAIN

This study analyses the spatial variability of runoff and erosion rates in vineyards due to mechanisation works. Runoff samples were collected at three positions in two plots after 33 erosive events in three years (2001, 2003, 2004) with different rainfall patterns. Three replications were considered at each position. Soil properties were evaluated in order to analyse its relationship with runoff and erosion rates. Runoff and erosion rates were, on average, higher in the levelled plot (HD), ranging between 8.4 and 34.3 per cent, than in the non-levelled plot (LD) ranging between 8.2 and 24.1 per cent. Mean sediment concentration in runoff ranged between 6 and 8 g L(-1) in the HD plot and about 4.6 g L(-1) in the LD plot, but with high differences within the plot. In the HD plot, runoff-rainfall rates were significantly higher (at 95 per cent level) in the upper part of the slope and decreased along the slope, while in the LD plot, differences in runoff rates were not significant and similar to those observed in the less disturbed areas of the HID plot. The higher susceptibility to soil sealing in areas where the original topsoil was removed conditioned runoff rates. In the lower part of the HD plot runoff rates were, on average, 20 per cent lower than in the upper part of the slope. In those positions runoff rates Lip to 79 per cent were recorded. Organic matter content and water retention capacity at different potentials are the soil characteristics related to the differences on runoff and erosion rates in the resulting soils. Copyright (C) 2009 John Wiley & Sons, Ltd.