Effect of irrigation and timing and type of nitrogen application on the biochemical composition of Vitis vinifera L. cv. Chardonnay and Syrah grapeberries.

This study reports the effect of different doses of nitrogen applied to soil and/or leaves of Syrah and Chardonnay grapevines in the Languedoc-Roussillon (France) over two years. In 2011, nitrogen treatment involved both foliar urea sprayings and soil application at two different levels, with two controls - irrigated without nitrogen and no irrigation nor nitrogen. In 2012, the same grapevines received either soil or foliar nitrogen using the same controls. Results showed that foliar application increased the amino acid content to a greater extent than soil application, but that a combination of both was the most effective. For the first time, significantly elevated proline levels in response to drought were demonstrated for the grapevine. Increased contents of aromatic compounds and glycosylated precursors closely mirrored the applied nitrogen dose. Wines produced from N-fertilized Syrah grapes in 2011 showed a statistically significant effect of irrigation and fertilization on positive sensorial perception.