Viticultural practices for enhancing quality

Transcription

1 Viticultural practices for enhancing quality Pr. Cornelis (Kees) van Leeuwen Bordeaux Sciences Agro Univ. Bordeaux www-ecole.enitab.fr/people/kees.vanleeuwen/ 1

2 Outline Resources vs quality output Management of temperature in various spatial scales Choice of grape variety Canopy management Climate change Management of light Training system C0 2 Photosynthesis Carbon allocation H 2 O Effect of vine water status on quality Vine water status assessment H 2 0 management Minerals with particular focus on N Effect of vine N status on quality Vine nitrogen assessment N management 2

3 Introduction Viticulture : produce high quality grapes at economically sustainable yields Quality and wine style Red wine : balanced sugar / acid ratio, skin phenolics, aroma compounds White wine : balanced sugar / acid ratio, aroma compounds Viticultural management Uptake of resources Transforming resources into quality and yield 3

4 Resources light water CO 2 temperature Grape quality potential Management practices Wine quality water minerals Each terroir offers a different set of resources Viticultural management aims to optimize quality and yield given the 4 available resources

5 Temperature 5

6 Temperature is a major driver of vine development and grape ripening Quality is obviously linked to temperature Too low : lack of ripeness Too high : unbalanced wines, lack of aromas However, relationship is complex High variation in temperature range among high quality wine producing regions 6

7 Temperature can be considered at various scales Macro climate scale : differences between wine growing regions (Burgundy vs Bordeaux) Meso climate scale : differences within wine growing regions Topo climate scale : differences linked to topography (Mosel) Micro climate scale : differences linked to canopy management 7

8 Managing temperatures at the macro climate scale Optimum ripening conditions for quality : «In a given region, the best wines are obtained from fine grapevine varieties that just achieve full ripeness under the local climatic conditions, as a quick ripening would burn the flavours that account for the finesse of great wines» Ribéreau-Gayon and Peynaud, 1960 Precocity is highly variable among grapevine varieties 8

9 To achieve high quality and terroir expression : Grapes must attain full ripeness Grapes should not ripen too early in the season, because quick fruit ripening in warm conditions limits aroma synthesis To achieve high terroir expression, precociousness of the grapevine varieties should match local climatic conditions, so as to obtain full ripeness at the end of the season (10 September - 10 October on th Northern Hemisphere of March on the Southern Hemisphere) 9

10 This is the case : In all European appellations, where growers have chosen by trial and error the varieties that best express terroir Harvest is always between September 10 and October 10 from the Mosel in Germany to Alicante in the South of Spain 10

11 To adapt variety to climate : use of Huglin Index Temperature assessment by means of an agroclimatic index, e.g. Winkler or Huglin index Heat requirements of grapevine varieties 11

12 Calculate index for a given winegrowing region, then choose grapevine variety 12

13 Around the world Regions that are structurally limited in their potential for growing high quality 13 wines

14 Varietal wines This balance between climate and precocity of the variety has been established by trial and error in most wine growing regions (Appellations in Europe, New Zealand ) Some exceptions are varietal wines produced from early ripening varieties in warm climates : the case of Chardonnay The Napa experience 14

15 Managing temperatures at the meso climate scale Inside a winegrowing region temperature differences can be considerable These meso climatic differences can be managed by variety choices Precocity: Sauvignon blanc < Semillon < Merlot < Cabernet franc < Cabernet-Sauvignon Benjamin Bois,

16 Managing temperature differences at the topo climate scale Mosel, photo Hans Schultz Topography has a great influence on local temperature ranges In cool climates, site selection is obviously very much based on topography 16

17 Managing temperatures at the micro climate scale Trunk height (Médoc) Fruit exposure through vigour management Leaf removal 17

18 The challenge of climate change Viticultural adaptations are needed to maintain the ripening period between September 10 and October 10 (or March on the Southern hemisphere) 18

19 Adopt later ripening varieties Some regions have existing resources Bordeaux : more Cabernet-Sauvignon and Petit Verdot In Languedoc: more Mourvèdre (Monastrell) Others don t Burgundy: which variety can replace Pinot noir and Chardonnay? 19

20 Site selection Plant Sauvignon blanc in Bordeaux on North facing slopes (topo climatic adaptation) Quality potential may increase in some less reputated areas (meso climatic adaptation) Benjamin Bois,

21 Use later ripening root stocks 420A 41B Select later ripening clones 240 Evolution de la teneur en sucres réducteurs des clones de Cabernet franc (parcelle CF22'05, 2009) Sucres réducteurs (g/l) /08/ /08/ /08/ /09/ /09/ /09/

22 Adapt viticultural practices Most viticultural practices used in temperate climates speed up grape ripening: shoot positioning leaf and fruit exposure leaf removal grape thinning With the perspective of global warming, the use of these viticultural practices should be reevaluated 22

23 Light 23

24 Light : an essential resource Light is the driving energy of photosynthesis Light infuences the amount of skin phenolics Light is impacted by environmental factors : Sunlight hours Clear sky / overcast sky Day length Slope and aspect Shading Light on the leaves and grapes is impacted by training system and canopy management Light and temperature are often (but not always) closely related 24

25 Manipulating light by training system and canopy management Exposure of leaves and grapes to sunlight can be manipulated considerably by training system and canopy management This has major implications on fruit quality 25

26 Leaves are «solar cells» H -H = Foliage Heighth -e = Foliage width -d = Intervine spacing -T = porosity (% gaps) -E = Row spacing m 2 par hectare E 0,6 < H/E < 1,0 26

27 H How to calculate Exposed Leaf Area (Murisier, 1996) e T -H = Foliage Heighth -e = Foliage width -d = Intervine spacing -T = porosity (% gaps) -E = Row spacing m 2 par hectare E ELA (m 2 /ha) = (2H + e)*(1 - %T)*10 000/E 27

28 Rules for a good canopy : «Sunlight into wine» (Smart and Robinson, 1991) High leaf area per hectare Leaf area per pruit weight ratio Avoid interior leaves Avoid bunch shading (except in excessively warm and sunny climates) 28

29 Leaf Area to fruit weight ratio 22,5 Degré probable (brix) 22,0 21,5 21,0 20,5 20,0 19,5 Ideally > 1.5 m 2 /kg 19,0 0,6 0,8 1 1,2 1,4 1,6 1,8 Surface foliaire totale (m2) /kg de raisin Tandonnet

30 Phenolics are linked to fruit and leaf exposure 290 Teneur en anthocyanes (mg/100g de baies) R2 = Eclairement moyen du feuillage (µe/m2/s) Carbonneau

31 High density is an efficient way to increase leaf area / fruit weight ratio Surface foliare / Poids de récolte (m 2 /kg) en fonction de la densité de plantation Surface foliare / Poids de récolte (m 2 /kg) 2,5 2 1,5 1 0, Densité de plantation (ceps /ha) Hunter and Archer, South Africa 31

32 Yield AND quality can be higher at high densities Rendement par hectare en fonction de la densité de plantation 25 Rendement (T/ha) Sugar Densité de plantation (ceps /ha) Teneur en sucre du raisin en fonction de la densité de plantation Yield Teneur en sucre ( Brix) Densité de plantation (ceps /ha) Anthocyanin Anthocyanes (D520) du raisin en fonction de la densité de plantation 4 D Hunter and Archer, South Africa Densité de plantation (ceps /ha)

33 At low densities, devided canopies increase leaf area / hectare GDC trellis Scott Henry trellis Lyre trellis 33

34 CO 2 34

35 CO 2 is : The brick from which sugars are made during photosynthesis Levels are homogeneous worldwide (380 ppm) but increase over time Enters the leaves through stomata Stomatal aperture is controlled by water CO 2 uptake cannot be controlled independently from water 35

36 Photosynthesis vs vine water status Niveau de photosynthèse mesuré sur 3 sols à Saint-Emilion le 31 août 2010 (cépage Cabernet franc) 14 Photosynthèse (µmol m -2 s -1 ) Graves Sable avec nappe Argile Gravel, severe water deficit Soil with water table, no water deficit Clay, mild water deficit 36

37 H 2 O 37

38 The water cycle takes place in the Soil Plant Atmosphere Continuum (SPAC) ATMOSPHERE Balance radiative Chaleur T a Vapeur e a Rnf H T fs r Ha H f r Hf T f e(t f ) r S Tr r Vf r Va e fs ET Figure: Ph. Pieri Rns H s T s r Hs G Sol r Vs e s E s 38

39 Impact of vine water status on vine development and grape quality 39

40 Shoot growth cessation and water deficit are highly correlated Correlation between shoot growth cessation and minimum stem water potential (Merlot, 2000) R 2 = 0,6986-2,0-1,5-1,0-0,5 0,0 Stem water potential (MPa) Shoot growth cessation (day of the year) Trégoat et al., 2002 JISVV 40

41 Berry growth and water deficit are highly correlated Correlation between berry weight and minimum stem water potential (Merlot, 2000) R 2 = 0,7578 2,0 1,8 1,6 1,4 1,2 Berry weight (g) -2,0-1,5-1,0-0,5 0,0 Stem water potential (MPa) 1,0 Trégoat et al., 2002 JISVV 41

42 Berry sugar content and water deficit are highly correlated, but this correlation is not linear Correlation between berry sugar content and minimum stem water potential (Merlot, 2000) R 2 = 0,7132-2,0-1,5-1,0-0,5 0,0 Stem water potential (MPa) Berry sugar content (g) Trégoat et al., 2002 JISVV 42

43 Berry anthocyanin content and water deficit are highly correlated Correlation between berry anthocyanin content and minimum stem water potential (Merlot, 2000) R 2 = 0,7799-2,0-1,5-1,0-0,5 0, Anthocyanin (g/kg) Stem water potential (MPa) Trégoat et al., 2002 JISVV 43

44 The paradox of the effect of water deficit stress in viticulture Despite its limiting effect on vine photosynthesis, water deficit improves quality in red table wine production This can be explained by the beneficial effect on berry size and shoot growth cessation 44

45 When the intensity of water deficit increases, shoot growth is reduced before photosynthesis Increasing water deficit Increasing water deficit FTSW Pellegrino et al., 2006 Europ. J. Agronomy 45

46 Management of vine water status 46

47 Water potential It is possible to measure water potential in vine organs Tool : pressure chamber Easy to measure Good precison, covers a wide range of water deficits Equipment is affordable for a winegrowing estate Water potential measurement has become the technique of reference 47

48 Stem water potential is a useful tool : Potentiel tige (MPa) 0,0-0,2-0,4-0,6-0,8-1,0-1,2-1,4-1,6 Juin Juillet Août Septembre Octobre To assess the evolution of vine water status during a vintage -1,8-2,0 0,0-0,2 Juin Juillet Août Septembre Octobre Sol graveleux -0,4 Sol sableux avec nappe d'eau To assess the evolution of vine water status as a function of soil type Potentiel tige (MPa) -0,6-0,8-1,0-1,2-1,4 Sol argileux -1,6-1,8-2,0 48 Van Leeuwen et al., 2009 JISVV

49 It s also a very good tool to manage irrigation Pre Dawn Leaf Water Potential and Stem Water Potential for two levels of irigation (Grenache, Roumanissas, Languedoc, 2006) ,2 Rainfall and irrigation (mm) ,4-0,6-0,8-1 -1,2-1,4-1,6 Water potential (MPa) Rainfall Irrigation Low Irrigation Stem Ψ Low Irr. Pre Dawn Leaf Ψ Low Irr. Stem Ψ Irr. Pre Dawn Leaf Ψ Irr. 0 June July August September -1,8 Données: Olivier Trégoat et Nicolas Cellié (Languedoc) 49

50 Carbon isotope discrimination: an easy touse reliable indicator of vine water status Ambient CO 2 contains 98.9% of 12 C and 1.1% of 13 C During photosynthesis 13 C, heavier than 12 C, is discriminated This isotope discrimination is reduced when stomata are closed (water deficit) => 13 C/ 12 C ratio in metabolites from photosynthesis indicate vine water status 13 C/ 12 C (called δ 13 C) is expressed in against a standard Range of values for δ 13 C : Van Leeuwen et al. 2001; Gaudillère et al

51 Le δ 13 C is highly correlated with stem water potential and with the level of photosynthesis Corrélation entre le potentiel tige mesuré le 31 août 2010 et le δ 13 C mesuré sur les sucres du moût à maturité Potentiel tige (MPa) -2-1,8-1,6-1,4-1,2-1 -0,8-0,6-0,4 R 2 = 0, δ 13 C (p. 1000) Corrélation entre le niveau de photosynthèse mesuré le 31 août 2010 en -28 début d'après-midi et le δ 13 C mesuré sur les sucres du moût à maturité van Leeuwen and Destrac, Saint-Emilion, 2010, unpublished data Photosynthèse (µmole*m -2 *s -1 ) R 2 = 0, δ 13 C (p. 1000)

52 δ 13 C is a useful tool to validate irrigation strategies Pre Dawn Leaf Water Potential and Stem Water Potential for two levels of irigation (Grenache, Roumanissas, Languedoc, 2006) ,2 Rainfall and irrigation (mm) ,4-0,6-0,8-1 -1,2-1,4-1,6 Water potential (MPa) Rainfall Irrigation Low Irrigation Stem Ψ Low Irr. Pre Dawn Leaf Ψ Low Irr. Stem Ψ Irr. Pre Dawn Leaf Ψ Irr. 0 June July August September -1, Irrigation 80 mm: δ 13 C = Irrigation 30 mm: δ 13 C = Data: Olivier Trégoat and Nicolas Cellié (Languedoc) 52

53 δ 13 C allows spatialisation of vine water status at the estate level δ 13 C Soil type Van Leeuwen and Pernet, unpublished data 53

54 Adapting plant material and training systems to vine water status Root-stock Grapevine variety Training system (leaf area) Yield reduction Irrigation 54

55 Root-stock effect SO4 110R Adelaide Hills, Australia Photo : Hans Schultz 55

56 Grapevine variety effect Merlot Grenache Appellation: Campo de Borja, Aragon, Espagne Average annual rainfall: 350 mm Photograph taken on 10 Septembre 2006 Photo : Miguel Lorente 56

57 Soil selecton In dry climates, do not plant vines on soils with low soil water holding capacity Calcaire Urgonien in Languedoc Example of la Clape (Coteaux du Languedoc) 57

58 Effect of training system Which training system in dry climates? Bush vines have low water needs. Productions costs are low, but so are yields Cordon trained, irrigated vines consume much more water, produce higher yields, but at higher production costs 58

59 Some questions about irrigation Do we need to irrigate a drought resistant crop in the context of rarifying water resources? Is irrigation sustainable? Increases soil salinity In Australia, some poorly irrigated vineyards have become unsuitable for viticulture Does irrigation really increase wine quality? In most irrigation trials, the unirrigated control produces grapes wth higest anthocyanins and total phenols How much does irrigation increase production costs? 59

60 Deficit irrigation Irrigation reduces wine quality when vines have unlimited water supply It is possible to produce high quality wines under irrigation, when water deficit is maintained. Irrigation is only applied to avoid severe water deficits This type of deficit irrigaton limits the use of water (often not more than 30 mm a year) and has a low environmental impact Deficit irrigaton can be managed with stem water potential measurements Irrigation can be controlled with δ 13 C after harvest 60

61 Nitrogen 61

62 Effect of nitrogen on vine vigour Correlation between must total nitrogen at harvest and pruning weight Pruning weight (kg/vine) 0,5 0,4 0,3 0,2 0,1 0 R 2 = p < 0, Must total nitrogen (mg/l) Choné et al.,

63 Effect of nitrogen on quality potential in red wine N-tester values Assimilable must nitrogen (mg N/L) Shoot growth cessation (day of the year) Yield (kg/vine) Berry weight (g) Grape sugar (g/l) Anthocyanin (mg/l) Total Phenolics Index Total acidity (g tartrate/l) Low N (4A) High N (4B) Malic acid (g/l) Trégoat et al.,

64 Effect of nitrogen on quality potential of Sauvignon blanc Fertilisation of 60 kg N / ha in a plot with N deficiency When fertilised, more aromas P-4MMP (ng eq/l) P-4MMPOH (ng eq/l) P-3MH (ng eq/l) Indice de polyphénols totaux Glutathion 0 N (carence) 405 (a) 760 (a) 3358 (a) 0,28 (a) 18 (a) 60 N (fertilisation) 715 (b) 2059 (b) (b) 0,21 (b) 120 (b) Choné et al.,

65 Assesment of vine N status Leaf blade total N content Leaf petiol total N content Grape must N content Leaf blade coloration measured by N- tester device 65

66 Low (cover crop) high heterogeneous Spatial variability of vine N status in a 37 ha estate Assessed by means of must assimilable N content (10 analyses / ha) 66

67 Management of vine nitrogen status To increase vine N status : Fertilisation Organic Long term effect Mineral Quick effect Soil based Leaf based To decrease vin N status : Cover crop Moderate to low N status can be a quality factor in red wine production Cover crop can reduce aroma potential in Sauvignon blanc 67

68 Conclusion Vines take up resources from the natural environment (temperature, light, CO 2, water, nitrogen) For some resources, a limited offer can be a quality factor (temperature, water, nitrogen) To a certain extent, resource uptake can be manipulated by vineyard management Measurement of resources, or of vine status with regard to resources, is critical for accurate management 68