Abstract
<p style="text-align: justify;"><strong>Aims</strong>: Agroscope investigated the impact of the leaf-to-fruit ratio on nitrogen (N) partitioning in grapevine following a foliar urea application with the aim of increasing the yeast assimilable nitrogen (YAN) concentration in the must. <strong></strong></p><p style="text-align: justify;"><strong>Methods and results</strong>: Foliar urea was applied to field-grown <em>Vitis vinifera</em> L. cv. Chasselas grapevines as part of a split-plot trial with two variable parameters: canopy height (90 or 150 cm) and fruit load (5 or 10 clusters per vine). Foliar application of 20 kg/ha of <sup>15</sup>N-labelled urea (10 atom% <sup>15</sup>N) was performed at veraison. The isotope labelling method allowed to observe foliar-N partitioning in the plant at harvest. The leaf-to-fruit ratio varied between 0.4 and 1.6 m<sup>2</sup>/kg, and strongly impacted the N partitioning in the grapevines. Total N and foliar-N partitioning was mainly affected by the variation of canopy height. The YAN concentration varied from 143 to 230 mg/L (+60 %) depending on the leaf area. An oversized canopy (+31 %DW) induced a decrease in the total N concentration of all organs (-17 %), and a decrease in YAN quantity in the must in particular (-53 %). A negative correlation between the N concentration and the carbon isotope discrimination (CID) could be pointed out in a condition of no water restriction (e.g., R<sup>2</sup> = 0.65 in the must).<strong></strong></p><p style="text-align: justify;"><strong>Conclusion</strong>: An excessive leaf area can induce YAN deficiency in the must. Thus, a balanced leaf-to-fruit ratio – between 1 and 1.2 m<sup>2</sup>/kg – should be maintained to guarantee grape maturity, YAN accumulation in the must and N recovery in the reserve organs. <strong></strong></p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results of this study encourage further research to understand the role of other physiological parameters that affect N partitioning in the grapevine – YAN accumulation in the must in particular – and add new perspectives for N management practices in the vineyard.<strong></strong></p>
Highlights
ConclusionUne surface foliaire excessive peut entraîner unecarenceenYANdanslemoût.Unrapportfeuille-fruit équilibré – entre 1.0 et 1.2 m2/kg – doit être maintenu de façon à garantir la pleine maturation des raisins, l’accumulation du yeast assimilable nitrogen (YAN) dans le moût et le stockage de N danslesorganesderéserves
Significance and impact of the study:Theresultsofthis study encourage further research to understand the role of otherphysiologicalparametersthataffectNpartitioningin thegrapevine–YANaccumulationinthemustin particular – and add new perspectives for N management practicesinthevineyard
N wasappliedtothecanopy(treatmentsB,C,DandE)ata dilutionrateof3.3 %(w/v).Themethodofisotopic labelling allowed the tracking of urea N in the plant and the description of its partitioning in the grapevine organs depending on the leaf-to-fruit ratio
Summary
Une surface foliaire excessive peut entraîner unecarenceenYANdanslemoût.Unrapportfeuille-fruit équilibré – entre 1.0 et 1.2 m2/kg – doit être maintenu de façon à garantir la pleine maturation des raisins, l’accumulation du YAN dans le moût et le stockage de N danslesorganesderéserves. Signification et impact de l’étude:Cetteétudeencourage le développement de la recherche afin de comprendre le rôled’autresfacteursphysiologiquesdansladistributionde N dans la vigne, et dans l’accumulation du YAN dans le moût en particulier. Nitrogen(N)represents1to4 %ofthedryweightofthe vine and plays a key role in the plant development, as a componentofproteins,DNAandchlorophyll.The optimization of N fertilisation practices in viticulture is required for quality and sustainability of the production whilepreservingtheenvironment(Champagnol,1984).In particular, the concentration of yeast assimilable nitrogen (YAN)inthemustatharvestisarelevantparameterused to determine wine quality because both its concentration and composition affect the alcoholic fermentation and the formation of aroma compounds (Rapp and Versini, 1991 ; Bell and Henschke, 2005).
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