Effects of soil management on runoff and erosion response to rainfall events of sloping vineyards in the Monferrato area (NW Italy)

The climate changes have a considerable impact on runoff and soil erosion in hilly vineyards since rainfall erosivity is strongly related to rainfall intensity and precipitation patterns. Moreover, in sloping conditions, the erosional processes are highly affected by seasonal climatic fluctuations and soil management practices. The use of controlled grass cover in the inter-rows is one of the most used and effective soil conservation practices adopted in temperate climates, nevertheless, the protective effect of grass cover may decrease according to seasonal pattern. This study presents the results of two experiments recording runoff and soil losses in two rain-fed hillslope vineyards, with different row orientation, located in the Monferrato region, NW Italy. The objectives of the study are to compare the effects of different inter-row managements and rainfall characteristics on runoff and soil loss in hillslope vineyards. Rainfall, runoff and erosion were monitored in vineyard plots, managed with conventional tillage (CT) and grass cover (GC). The first experiment (75 events) was carried out in the Vezzolano Experimental Farm in the period 1992-1997 in two portion of a vineyard with rows along the contour lines. The second experiment (about 120 events) is currently running, since 2000, at the Tenuta Cannona Experimental Centre, and includes two plots with rows along the slope. The results related to the first experiment showed the fundamental role of contour-slope row orientation in reducing the water and soil losses. Nevertheless, very high erosion rates (up to 12.3 Mg ha-1) were observed in the tilled plots during a single storm. In the vineyard with rows along the slope the highest erosion rates observed were 21.2 and 3.4 Mg ha-1, in the CT and GC plot, respectively, and were observed during autumnal events. In both cases, the grass cover was especially effective in reducing soil losses during summer storms.