Modeling soil and nutrient runoff yields from an Italian vineyard using SWAT

In the Chianti Classico area (Tuscany, Italy), hillside vineyards are usually kept bare of vegetation and are thus prone to soil erosion and nutrient losses. The aim of this study was to develop Soil and Water Assessment Tool (SWAT) model parameters for predicting runoff sediment, and nitrogen and phosphorus losses from vineyards. Runoff volume and composition were measured during 87 rainfall events from January 2005 to December 2008 in an instrumented up-down slope vineyard at the University of Florence's Montepaldi Farm in Tuscany, Italy. Harrowed and grass cover interrow management techniques were evaluated. While the applicability of SWAT to simulate soil and nutrient losses was tested at a daily scale, the soil hydrology was tested using the Green-Ampt-Mein-Larson equation with a 10 min time step. The results indicated that the calibrated SWAT model overestimated runoff and soil loss by 15% to 20%. However, these deviations were considered satisfactory to good according to three commonly used statistical indices. The simulations of nitrogen and phosphorus losses were also satisfactory to good according to the statistical indices, one of which, the Nash-Sutcliffe coefficient, had values greater than 0.92 for the calibration and validation phases and for each management technique.