This review addresses the role of nitrogen (N) in vine balance and grape composition. It offers an integrative approach to managing grapevine N nutrition. Keeping in mind that N excess is just as detrimental to wine quality as N depletion, the control of grapevine N status, and ultimately must N composition, is critical for high-quality grape production. N fertilisation has been intensively used in the past century, despite plants absorbing only 30 to 40 % of applied N. By adapting plant material, soil management and vine balance to environmental conditions, it would be possible for grape growers to improve plant N use efficiency and minimise N input in the vineyard. Vineyard N management is a complex exercise involving a search for a balance between controlling vigour, optimising grape composition, regulating production costs and limiting pollution. The first part of this review describes grapevine N metabolism from root N uptake to vine development and grape ripening, including the formation of grape aroma compounds. The advantages and limits of methods available for measuring plant N status are addressed. The second part focuses on the parameters that influence grapevine N metabolism, distinguishing the impacts of environmental factors from those of vineyard management practices. Areas for further research are also identified.

Background and Aims:Yeast assimilable nitrogen (YAN) in grape must is an important determinant of wine composition. The effect of foliar nitrogen fertilisation on YAN concentration in must of Vitis vinifera L. cv. Chasselas was studied. Nitrogen assimilation and translocation were investigated by applying 15 N-labelled urea at flowering and at veraison. Methods and Results: Foliar urea was applied on field-grown Chasselas grapevines using labelled (10 atom% 15 N) and unlabelled urea. The vines were excavated at harvest, and plant parts were separated and analysed. Thus, the distribution of dry organic matter and of total organic carbon and total organic nitrogen in the plant at harvest was determined. Bunches were the strongest N sink among all of the organs during both fertilisation periods. The highest YAN in the must, however, was obtained when the urea was applied during veraison. Conclusions: Isotope labelling was used to describe N partitioning throughout the vine in response to foliar nitrogen fertilisation with urea at flowering and at veraison. Differences between organs in carbon and nitrogen isotope discrimination at natural abundance were established. Fertilisation with urea during veraison increased the YAN concentration in Chasselas grape must. Significance of the Study: Results show that it is more effective to correct YAN deficiency in the vineyard with application of foliar urea during veraison than during flowering.

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