Effect of nitrogen fertilization and water deficit on the quality of wines in relation to the biochemical composition of grapes of Vitis vinifera cv. Syrah

Abstract

Nitrogen management and water status of grapevines are determining factors in wine quality. The aim of this study was to determine the effect of different doses of nitrogen applied to the soil and leaves in plants under irrigation in a Syrah vineyard located in the INRA Pech Rouge experimental station in the Languedoc-Rousillon region (France) in 2011. The treatment with nitrogen involved both foliar urea sprayings and an ammonium nitrate application into the soil at two different doses: N1 (irrigated, with 2.5 kgN/ha foliar and 30 kgN/ha in soil) and N2 (irrigated, with 5 kgN/ha foliar and 60 kgN/ha in soil) and the controls N0 (irrigated, without nitrogen) and I0 (without irrigation nor nitrogen). Total acidity, pH, sugar content, berry weight and volume, aroma precursors and amino acid content, were determined in grapes, and fermentation aroma composition and a sensorial evaluation were performed in wine. This study showed that the major content of glycosylated aromatic precursors in grapes (specifically non terpene alcohols and monoterpenes) corresponds specifically to the treatments with nitrogen application in the absence of severe water deficit. In addition, a positive difference in the quality (particularly aroma intensity, olfactory quality and overall quality rating) of the wine produced from these grapes was observed by the tasting panel. These results can be explained to a certain extent by the effect of fermentative aroma presented in wines due to soil and foliar fertilization which raised the positively perceived aromas.