Canopy Management: Identifying the Problems and Practical Solutions

Keynote paper

Canopy management: identifying the problems and practical solutions

Richard E. Smart and Steve M. Smith Scientist, Viticulture and Technician, Viticulture MAFTech Ruakura Agriculture Centre Private Bag, Hamilton, New Zealand

Abstract This paper discusses the implications for yield and qual- The effects of improper canopy management ity of excessively dense canopies. Simple techniques are Shade depresses fruit bud initiation as is shown by recent presented to identify problem canopies including measure- reviews (Kliewer 1982; Shaulis 1982) so that training sys- ments of canopy surface area, visual assessment of cano- tems which reduce within-canopy shade lead to increased pies, point quadrat measurements, leaf area measurement yield. Bunch rot incidence is also increased by dense cano- and measurements at winter pruning. Results are presented pies (Rotem and Palti 1969) and perhaps many of the to show how problem canopies can be overcome, with effects noted of pruning level, rootstock and fertilisation emphasis on shoot devigouration by pruning level and may be indirect effects through canopy microclimate. Shade training system. The economic advantages of some new effects on fruit composition are increasingly being training systems are presented. acknowledged, and a recent review (Smart 1985a) indicates that shade causes inferior fruit composition. For example, Introduction shade causes increased pH and K and malic acid concen- Canopy management consists of deliberate decisions by tration, and reduced sugar, anthocyanin, phenol and fruit the viticulturist to achieve some desirable canopy configu- flavour concentrations. Light quality as well as light quan- ration, be it in terms of surface area, volume, leaf area per tity effects have recently been implicated as affecting grape- shoot, fruit exposure, shoot orientation or even vine phys- vine physiology, especially fruit ripening (Smart 1987b; iological status. Important to consider are the economic Smart 1987c). costs and benefits of "canopy management". Management Improper canopy management can cause increased includes concepts of problem identification and then their production costs also. For example, vines with long, heavy solution. I have observed (Smart 1987a) that many canopy canes can be more expensive to hand prune, and dense components are "under-managed"— for example shoot canopies can cause inefficiencies of spray application. Fur- orientation in Australian and Californian vineyards, where ther, modern canopy design aims to enhance mechanisa- shoot position is determined by the natural forces of gravity tion, especially for summer trimming and winter pruning and wind rather than the viticulturists intervention. along with fruit harvesting. Operations such as leaf pluck- Canopy management is being increasingly recognised as ing in the fruit zone are facilitated by orderly arrangement an important tool for manipulating wine grape yield and of shoots in the canopy. quality (Smart 1985a). This is not to suggest that canopy The appropriate management of dense shaded canopies management is the only factor to be considered in improv- is a major problem facing modern viticulture. In fact the ing wine quality. Planting with a high-health, genetically problem now is of higher incidence than ever before, due superior clone of the appropriate cultivar grafted to an to advances in virus elimination, fertilisation, irrigation, appropriate rootstock and matched to a suitable climate plant protection and weed control. In the past, inadequate is of paramount importance. Soil conditions are cultural methods caused devigouration and canopies were acknowledged also of being of considerable significance, often less dense. These problems are exacerbated in many particularly in interaction with the climate and manage- New World viticultural regions due to choice of excessively ment systems in regulation of water and mineral status. deep or fertile soils for vineyards. Such is commonly the Also important are timeliness of harvest, fruit protection case in New Zealand. and of course appropriate vinification and conservation. This paper will indicate the viticultural and oenological Identifying problem canopies implications of improper canopy management, how Canopy surface area determination problem canopies can be identified, and some practical and Canopy surface area can be determined by sketching the economic techniques of canopy management. The concept canopy end-section to scale and calculating the exposed of vineyard quality assurance will be introduced whereby surface area. Surfaces facing downwards are not included, using simple assessments the viticulturist is able to moni- though this ruling is recognised as somewhat arbitrary tor progress in canopy management. (Smart 1985a). Similarly, there is a small effect of row orientation which is ignored. Fig. 1 lists five sample canopy Proceedings Second international Cool Climate Viticulture and Oenology Symposium, Auckland, New Zealand. January 1988. gib Canopy management identifying problems ono solutions cross-sections and canopy surface area calculations for row scorecard has been modified over several years, and the spacings 1-3.6 m, and for divided and undivided canopies. MKIV version has eight characters each worth 10 points Dimensions for the first four trellises are given by Smart to be assessed, just before harvest. These are: canopy gaps, (1985a). These are: Bordeaux traditional, row spacing 1 m; leaf size, leaf colour, canopy density, fruit exposure, shoot Intermediate row spacing 2 m; Traditional (New Zealand), length, lateral growth, and growing shoot tip presence. row spacing 3m; and "U" or "Lyre" trellis with row spacing Table 1 shows the MKIV scorecard, with each parameter 3 m. The fifth design is the Ruakura Twin Two Tier (RT2T), assessed out of 10 points, for a total of 80. High scoring 3.6 m row spacing. It is a horizontally and vertically canopies have adequate canopy gaps, slightly small leaves, divided trellis under evaluation at Rukuhia Horticultural dull but green healthy leaves, low leaf layer number, high Research Station, New Zealand (Smart 1987a). fruit exposure, intermediate shoot length, limited or zero lateral growth and no growing shoot tips. This scorecard is being used to evaluate experimental and commercial vineyards, and is proving a useful tool to determine management strategies. Row spacing •1m Canopy SA•I9,000 m2/ha Point quadrat assessment x/h•088 This technique uses a long (ca. 1 m) thin (ca. 3 mm) straight, sharpened metal rod inserted through the canopy to record "contact" with canopy components (fruit and leaves— shoots can generally be ignored). For vertical cano- Row spacing • 2m pies, the rod is inserted horizontally in the fruit zone. For I Canopy SA •18,000 m2/ha x/h .1 00 non-vertical canopies, the rod is inserted at an angle (say 45-600) towards the fruit zone. By recording contacts as the rod progresses, and with a sample of say 100 insertions per canopy, the following can be readily calculated: Row spacing ■ 3m Canopy SA • I2,330 m 2/ha Percent gaps—number of insertions with no contact/100. x/hal.56 Leaf layer number (LLN)— total number of leaf contacts for all insertions/100.

Row spacing • 3 m Percent interior fruit—number of contacts with fruit not Canopy SA 223,330 m 2/ha at the canopy exterior divided by total number of fruit x/h• 0.5 contacts. Percent interior leaves— number of contacts with leaves not at the canopy exterior divided by total number of I RT2T" leaf contacts. Row spacing • 3.6m Canopy SA • 21,110 m 2/ha These measurements and calculations can be readily x/h • 100 made, and provided sampling is adequate can accurately describe canopies. Fig. 2 shows the results of assessing five experimental Fig. 1. Vineyard cross sections drawn to scale, and calculated canopy sur- Cabernet Franc canopies at Rukuhia. The higher LLN of face area and ratio x/h (see text). standard vines was associated with lower canopy gaps, and The small canopy surface area of traditional, undivided higher proportions of interior leaves and clusters. The con- canopies is apparent, a primary cause of canopy shading. verse was true for RT2T vines with the low mean LLN of Sunlight interception will be proportional to this value. 0.73. Note that the proportion of interior fruit is about Canopy surface area is increased by decreasing row spac- twice that of interior leaves, due to the fact that leaves are ing, or by canopy division as for the "U" and "RT2T". The able to adjust their position to optimise illumination and ratio of distance between canopies (x) to their height (h) clusters cannot (Smart et al., 1982). is important. Smart (1985b) has suggested that when this Leaf area assessment value is less than 1.0 then shading at the base of canopy walls may be excessive. For this reason, the value of canopy Shoot leaf area can be readily calculated by comparing surface area for the RT2T (21, 110 m 2/ha) is at about the the fresh weight of a known number of discs of known maximum value possible. area (cut with a cork borer) to the fresh weight of leaves. Leaf area can also be measured with electronic meters and Visual assessment of canopies by correlations with length measurements. It is instructive Canopy gaps, canopy density and fruit exposure can be to separate main and lateral leaves, and also to record shoot readily visually estimated. This leads to the concept of a length. Sufficient shoots need be sampled to obtain a "vineyard scorecard" first developed in South Australia in meaningful average. Leaf area per. vine can be calculated 1981 (Smart et al., 1985). With sufficient instruction and by multiplying with the average shoot number per vine. experience, scorers can give similar answers. Estimates of The ratio of leaf area to canopy surface area (LA/SA) can canopy density can be incorporated with other visual esti- be then determined. Ideal values of this figure should be mates of physiological significance to make an assessment 1.2 or lower (Smart 1984); note that for tall thin canopies of the potential winegrape quality from the vineyard. The LLNZ 2 x LA/SA.

110 Proceedings Second International Cool Climate Viticulture ona Oenology Symposium. Auckland. New Z, Canopy management identifying problems and solutions

Table 1. Ruakura vineyard ernrecard (MK IV). This scorecard should be used just before harvest. NB: If majority of shoots are less than 30 cm long, or if these vines are clearly diseased, or chlorotic or necrotic, or excesively stressed, DO NOT SCORE VINEYARD.

A. Assessed standing away from canopy 1. CANOPY GAPS (from side to side of 5. FRUIT EXPOSURE (remember that the canopy, within area contained by canopy has two sides normally: 90% of canopy boundary) score: that fruit which is not exposed • < 40°/s 10 on your side may be exposed to • about 50°/s 8 the other side score: • about 30°/s 6 • about 6007o or more exposed 10 • about 20°/s 4 • about 50% 8 • about 10070 or less 0 • about 40°/s 6 • about 30% 4 2. LEAF SIZE (basal-mid leaves on • about 20% or less 2 shoot, exterior). For this variety are the leaves: 7. LATERAL GROWTH (normally from • slightly small 10 about point where shoots trimmed. • average 8 If laterals have been trimmed, • slightly large 6 look at diameter of stubs) • very large 2 • limited or zero lateral growth 10 • very small 2 • moderate vigour lateral growth 6 • very vigorous growth 2 3. LEAF COLOUR (basal-mid exterior leaves, in fruit zone) 8. GROWING TIPS (of all shoots, the • leaves green, healthy, 10 proportion with actively growing slightly pale, dull tips - make due allowances for • leaves dark green, shiny, 6 recent trimming) healthy about 5elo or less 10 • leaves yellowish green, healthy 6 • about 10% 8 • leaves with mild nutrient 6 • about 20% 6 deficiency symptoms • about 30% 4 • unhealthy leaves, with marked 2 • about 40% 2 necrosis or chlorosis • about 50 07o or more 0

B. Assessed standing at canopy Total point score /80 4. CANOPY DENSITY (from side to side, in fruit zone), mean leaf layer number (LLN) • about 1 or less 10 • about 1.5 8 • about 2 4 • more than 2 2

Similarly the shoot descriptor gamma (X, the ratio of leaf to be more widely spaced, and less vigorous shoots can area/shoot length, units cm) can be derived from the above be more closely spaced, to produce a desirable LLN of 1.5. measurements. This can then lead to calculations of desira- Pruning weights in excess of 1.0 kg/m cordon length have ble shoot spacing, using relations developed by Smart previously been associated with excessively dense canopies (1985a), Smart et al., (1987). For uniform vertical shoots (May 1973) but recent studies have suggested that this figure arising along a line and D cm apart, with leaves inclined should be 0.5 kg/m or less for trimmed Gewurztraminer at a mean angle 8 to the horizon, then and Cabernet Franc canopies (Smart, unpublished data) LLN sin 8/1) (1) to retain optimal canopy microclimate. Whether shoots are For an optimal LLN of 1.5 (Smart 1987a), and for meas- trimmed or not, and whether shoots are vertically displayed ured values of gamma and , the optimal shoot spacing can or not will affect this critical value. be calculated. Data from a study with the cultivar Shiraz in Australia (Smart 1982) have shown a correlation of pruning weight Winter pruning assessments and vine leaf area with 1 kg pruning weight approximately During winter pruning the number of shoots growing equivalent to 10 m 2 leaf area. Recent studies with the cul- the previous season can be counted, and pruning weight tivar Cabernet Franc show a ratio of 5-10 m 2/kg. of 1 year old wood determined. Then by division the mean The pruning weight data can be combined with yield shoot weight can be calculated. These three parameters measurements of the previous vintage to provide a ratio (shoot number, pruning weight, mean shoot weight) can of yield/pruning weight. Bravdo et al., (1984) have recently be used to indirectly assess canopy microclimate. Unpub- shown that values of the ratio of yield to pruning weight lished studies by the author suggest an optimal spacing for in excess of 10 is an indication of "overcropping"— that is moderate vigour and verticially trained Gewurztraminer a vine condition where there is insufficient exposed leaf shoots to be about 15 shoots/m; more vigorous shoots need area to adequately ripen the fruit. A yield/pruning weiolimr

Proceedings Second International Cool Climate Viticulture and Oenology Symposium, Auckland, New Zealand. January 1988. Canopy management: identifying problems and solutions

Overcoming problem canopies Shoot positioning 40 Canopy gaps Where canopies are not shoot positioned, as is com- • j monly the case in Australia and California, canopies can I L x have a large surface area although often also considerable 20 1 V• •14 x within canopy shading. Converting such canopies to ver- .AA x tically upwards shoot positioning may in fact reduce canopy X 0 o or 0 0 surface area and increase shading (Smart 1987a). In New Zealand, we have recorded modest yield and sugar con- 40 Interior leaves o centration gains by increasing canopy surface area with the o 0 Scott-Henry (or Smart-Henry) form of trellis conversion (Smart 1987a). With this system shoots from the bottom 20 0 x o0 cane are trained downwards to fill the gap which normally x x exists when all shoots are trained upwards. Then shoot den- 0 sity is effectively halved, and canopy surface area is almost doubled. 0 100 - Interior fruit Leaf plucking Papers to be presented elsewhere in this symposium by ! 80- 8 u_ Kliewer et al. and Smith et al. highlight the benefits to be 0 had from timely leaf removal in the cluster zone. So long 60- 0 0 as leaf removal is not so extensive as to reduce the leaf/fruit ratio below the critical level then this practice is effective • a TK3T • in increasing fruit exposure in otherwise "too dense" 40- a _ x TK2T a canopies. is"° x TAT x .66 L Shoot devigouration and pruning level 20- II -A RT2T Modern vineyards often have excessively leafy shoots for STD 0 reasons outlined in the Introduction. Lower vigour shoots • x o have smaller main leaves and fewer and smaller lateral o leaves. However, such shoots do not necessarily have lower LLN yield and lower vigour shoots can be more closely spaced to allow for high yielding vineyards yet without shaded microclimates. Other papers presented at this symposium Fig. 2. The relationship between LLN and fruit and leaf exposure assessed detail soil effects and cover crop effects on shoot devigou- by point quadrat. Cabernet Franc, Rukubia, 1987. ration. There is a well acknowledged effect of water defic': ratio of 10 corresponds to a leaf area/fruit weight ratio on shoot growth (Smart and Coombe 1983) and generally of 10 cm2/g fruit fresh weight (for 1 kg pruning weight:v., soil and cover crop effects can be explained primarily by 10 m2 leaf area) considered appropriate to effectively ripen effects on vine water supply. grapes (Shaulis and Smart 1974). We find a yield/pruning A multitude of pruning trials around the world have weight ratio of 8.5 about ideal for Cabernet Franc. shown that light pruning is effective in shoot devigoura- Mean shoot weight is a useful indicator of adequacy or tion. Recently these concepts have been further extended excess of vegetative growth. High values of mean shoot by the development of "mechanical" then "minimal" prun- weight can indicate excessively long (say more than 12-15 ing especially in Australia. Recent studies (Clingeleffer and nodes), excessively thick stems (say more than 10 mm Possingham 1987) have shown that minimal pruning leads diameter) or excessively leafy shoots with large main leaves to production of larger canopy surface area, especially early and excessive lateral growth. Mean shoot weight is a bet- in the growing season, from a larger number of smaller ter indicator than pruning weight since lightly pruned vines shoots. For example normal pruned Sultana vines had 77 can have high pruning weights though made up of large shoots per vine compared to 276 for minimal pruned, with numbers of individually smaller shoots (Clingeleffer and respective mean shoot weights of 31 and 3 g. Possingham 1987; Soderlund et al., 1987). Fig. 3 presents results of a pruning trial with the cul:i- We find for Cabernet Franc for example that a mean var Shiraz in the hot climate of Griffith, N.S.W. conducted shoot weight of 20-30 g corresponds to a desirable shoot during the 1969-70 growing season. Vines were 6 years old, vigour level and a well balanced vine, but that vines severely spaced 3.8 x 2.5 m and previously spur'pruned to 50 two- pruned and on the restrictive standard trellis have mean node bearers. Four treatments were imposed: pruning to shoot weight of 70 g. 50 nodes (buds), 150 nodes, 300 nodes or unpruned (about 1200 nodes retained). Yield increased with pruning level Vine development and fruit composition up to 300 nodes retained per vine, and sugar concentra- Excessively dense canopies can lead to susceptibility to tion declined slightly at high node numbers. The yield bunch rot and delayed maturity, i.e. lower sugar, higher increase is due to more bunches although bunch weight pH, malate and K. Associated with ripening delays is a decreased with more bunches per vine. Flower number per delay in development of woody tissue (periderm) on the bunch was independent of pruning level, but set was grapevine shoots after veraison. reduced by light pruning: reduced berry weight.aad berry

112 Proceedings Second International Cool Climate Viticulture and Oenology Symposium, Auckland, New Zealand •

Canopy management: identifying problems ana solutions

shade, but canopy curtains should be far enough apart to - 4 • 40 ensure no mutual shading of each other (Smart 1985b). • Canopy division typically promotes increases in yield and quality (Shaulis et al., 1966; Smart 1985a; Carbonneau et 20 al., 1978; Carbonneau 1985). Some of the "new" training systems can be completely mechanised for summer and winter pruning and harvesting i.e. GDC (Baldini 1982); some, like the U system (Carbonneau et al., 1978) and the o .0 4001 100 e rr••■.•• C o g E •4T, •-• TUT (Smart 1985b) require some machine modification CO co C before widespread use, and some, like the Tatura trellis (Van 0 //—.1 den Ende 1984) will be difficult to totally mechanise. 400 Improvements to training system are a principal means of potentially overcoming canopy shade problems for many 200 - [1.0 "•`' I vineyards. Our recent research however indicates that sim- C. 0 0 ple canopy division (say with 2 m canopy/m row length) CC1I • I 0 may not be sufficient to • overcome shading. The "new 20- 2000 generation" of trellis systems such as the RT2T, extensively "647 divided with 4 m canopy/m row, and using wide vine spac- • •-•-• o E o 10 - 1000 ° ings and large bud numbers per vine may be required on o 7/- - o very fertile soils to achieve a desirable microclimate. -J 0 It has been apparent for Cabernet Franc at Rukuhia that training systems with large exposed leaf areas (i.e. Tatura, 0 o; 1 RT2T) use water more quickly than standard vines and thus 100 5—EEo • C .1; water stress may be more readily induced, a considerable I , { 0 advantage when vineyards are grown in areas of high rain- 200 400 1200 fall and low evaporation. Carbonneau (1987) has recently Nodes per vine demonstrated the significance of leaf:root ratio of differ- Fig. 3. Yield, growth and fruit composition responses of Shiraz grape- ent training systems in Bordeaux. vines to pruning level. Griffith, N.S.W., 1969-70 Table 2 summarises the results of the 1986-87 growing number both contributed to reduced bunch weight. Light season for the Cabernet Franc trellis trial at Rukuhia. pruning caused effective shoot devigouration, with shorter Effects of training system and node number on yield, fruit shoots, fewer main and lateral leaves and reduced mean composition, shoot devigouration and canopy microclimate leaf area. are presented. Row by vine spacing is 3.6 x 2 m. "Small" This trial is indicative of vine response to a wide range and large" vines trained to RT2T differed in cordon length of node numbers in a hot climate, and demonstrates that and node number. Note that cordons were not fully estab- large node numbers per plant can lead to effective shoot lished for Tatura and RT2T large vines, so potential yields devigouration without yield loss. Similar principles apply in future will be greater. in cool climates, though fruit sugar levels are more likely Pruning weight per vine was relatively constant between to be depressed at high yields. A notable feature of this treatments (3.5 to 4.8 kg/vine) but mean shoot weight was trial, and others like it, is that canopy surface area is not much reduced by vines with large bud numbers, from 69 increased proportionally to node numbers retained. That g/shoot for standard vines to 23 g/shoot for Tatura. Due is, node number per vine is varied while vine spacing, or to restrictive cordon length, the yield of standard vines (11 more importantly canopy length (or area) per vine is cons- t/ha) was considerably inferior to RT2T (29 t/ha) and tant or nearly so. Hence large node and shoot numbers Tatura (40 t/ha). Measurements of yield to pruning weight, per vine are associated with increased canopy shading. The and shoot leaf area and its components indicated the extent Cabernet Franc experiment at Rukuhia is examining the of shoot devigouration obtained by RT2T and Tatura sys- notion of using large node number per vine to devigourate tems, and also by bud number per vine. The canopy shoots, but in turn making canopy length proportionally microclimate of the standard was inferior to other systems larger so that shoots are not crowded. In particular, the with higher LLN, fewer gaps and higher proportions of treatment RT2T involve vines with different cordon lengths interior leaves and fruit. While the Tatura trellis had wide and hence node numbers, but all at the same vine and node shoot spacing, shoots from adjacent cordons were inter- spacing. Effects of these treatments on shoot devigoura- mingled, and fruit tended to be located away from the tion are subsequently presented. upper canopy surface in the shade. This was implicated for example in the higher elo rot of fruit on the Tatura trellis 'training system at harvest. Since the description of the Geneva Double Curtain There was little effect of training system on fruit com- (GDC) trellis in 1966 by Shaulis and coworkers in the position at harvest, the most notable being increased pH eastern United States there has been an upsurge of interest for standard trained vines. in using training systems for canopy management. Smart Wine quality was assessed by experienced judges in (1987a) outlines principles for training system design to August 1987 for 1986 and 1987 wines produced using stan- improve yield and quality and to facilitate mechanisation. dard microvinification techniques. For both years, vines Canopy division can be effective in reducing within canopy trained on the Tatura trellis produced the most preferred

Proceedings Second International Cool Climate Viticulture and Oenology Symposium, Auckland. New Zealand. January 1988. )V° Canopy management . identifying problems and solutions Table 2. Effect of training system and vine bud number on yield, growth, canopy microclimate, fruit composition and wine quality of Cabernet Franc 198647 growing season.

Training system RT2T Standard "Small" "Large" Tatura LSD vines vines

Nodes per vine 47 83 154 238 8 Potential cordon 2 6 12 24 NA length/vine (m) Shoots per vine 54 96 156 207 11 Growth Pruning weight/vine (kg) 3.7 3.5 3.8 4.8 0.5 Mean shoot wt (g) 69 37 25 23 4 Yield/pruning ratio 2.0 4.9 7.4 6.0 NA Mean main leaf area (cm 2) 164 125 104 11 Lateral leaf area/shoot (cm 2) 1272 860 620 412 Total leaf area/shoot (cm 2) 3615 2443 2086 45 1 Leaf area/fruit wt (cm 2/g) 20.9 18.7 12.7 4.1 Microclimate Percent gaps 3.3 20.3 31.3 17.0 10.4 LLN 2.17 0.81 0.64 1.28 0.22 210 interior leaves 25 5 2 7 (41)' o interior fruit 71 13 4 21 (79)' 16 Shoots/m cordon 27 16 13 9 Yield Yield per vine (kg) 7.6 17.2 27.8 28.8 2.7 Yield (t/ha) 10.6 28.8b 28.8b 40.0 3.9 24 rot 2.5 1.3 0.8 4.7 2.9 Fruit composition (harvest) Sugar ( 013rix) 19.3 18.9 19.2 18.7 0.8 Titratable acidity (g/1) 8.6 8.4 8.1 8.5 0.7 pH 3.14 3.09 3.09 3.08 0.04 Mean berry wt (g) 1.58 1.60 1.70 1.41 0,14 Wine quality (score ex 20) 1986 vintage 13.1 14.0c 15.2 1.8 1987 vintage 13.7 12.8c 15.1 2.5 ° Values in brackets are estimates obtained when fruit and clusters at the bottom canopy surface are not counted as "exterior" °Since "large" and "small" vines are adjacent in one plot this yield is the equivalent of mean plot yield, with two small vines to each "forge'" vine `Fruit from large and small vines combined. wines, and in 1986 the standard trellis the least preferred. planting represented 64%. Planting on narrow rows would These results appear in contradiction with canopy tnicrocli, effectively double the per ha cost (to about NZS21,570/ha). mate measurements presented-especially for the 1986-87 Equivalent costs for the U trellis were NZ$11,435/ha, the growing season, since a high proportion of fruit on the GDC was NZ$10,638/ha and the TK2T was NZ$11,143/ha. Tatura trellis was shaded. We believe the reason for the Costs of the RT2T trellis with 3.6 m x 2 m spacing was apparent superiority of the Tatura trellis in these 2 years $10,625/ha. These figures demonstrate that close row spac- is the fact that water stress was evident for these vines in ing is more expensive than divided canopies in terms of both years, reducing active shoot growth and berry weight. vineyard establishment. The economic advantage of This water loss was a result of the largest exposed leaf area improved training system design over the standard was of all treatments. clearly demonstrated by Crawford, being due primarily to Vineyard economics increased yield. For example, Cabernet Franc vines trained Improved training systems require typically an increased to the standard trellis had an accumulated cash flow after capital expenditure at planting, due to requirements for 10 years of NZ$58,700/ha while for the RT2T the figure more wire, posts and/or crossarms. For close row spacing was NZ$114,500/ha. designs, there is an increased plant cost, especially signifi- Conclusion cant when using grafted plants. Canopy shade is a common problem in New World vine- In general, the efficient viticulturist cannot afford not yards which can cause reductions in vineyard yield and to make this initial capital investment as vineyard returns winegrape quality. Practical techniques are presented as to are significantly increased. This is due primarily to how problem canopies may be identified and subsequently increased yield and hence return, though perhaps also for how they may be remedied. I propose that more attention bonus payments for increased quality and in some instances be paid to "quality assurance" in the vineyard - using the increased adoption of machines. described techniques to identify problems then appropri- In a recent comprehensive study of the economics of ate management strategies to overcome them. Of the training systems Crawford (1987) has shown that cost of management strategies discussed, the use of large vine spac- establishing a vineyard in New Zealand trained to the stan- ing with concomitant large node numbers and extensive dard trellis (3m x 1.5m) is NZ$3.55/m row or canopy surface area offers opportunity to devigourate NZ$10,786/ha of which the costs of grafted plants and shoots and to induce water stress, important in _areas of

114 Proceedings Second International Cool Climate Viticulture and Oenology Symposium. Auckland. New Zealand Canopy management: identifying problems and solutions high rainfall, high soil water storage and low evaporation. Smart, R.E.. Shaulis. N.J. and Lemon, E.R. The effect of Concord vine- The current fad of using close row spacing is likely to yard microclimate on yield I. The effects of pruning, training and shoot positioning on radiation microclimate. Am. J. Enol. Vitic. 33: 99-108 (1982). achieve only limited devigouration (see for example Remoue and Lemaitre 1985), but substantially increased costs of Smart, R.E. Vine manipulation to improve wine grape quality. In: Webb, vineyard establishment. A.D., Ed. Grape and wine centennial symposium proceedings; 18-21 June 1980; Davis, CA: University of California, Davis, CA: 362-75 (1982).

Acknowledgements Smart. R.E. and Coombe, B.G. Water relations of grapevines. In: The authors would like to acknowledge the assistance of Kozlowski, T., Ed. Water deficits and plant growth. Academic Press, Lon- Gary Woodbury and staff at Rukuhia Research Station, don: 137-96 (1983). and Isabelle Gravett and Phil Allison for biometrical anal- Smart, R.E. Canopy microclimates and effects on wine quality. In: Lee. ysis. Geoff Kelly chaired the tasting panels. Tom van Dam T.H. and Somers, T.C., Eds. Advances in viticulture and oenology for and Brent Fisher made the experimental wines. economic gain. Proceedings of the fifth Australian wine industry technical conference; 29 November-I December 1983; Perth, WA: The Australian Literature cited Wine Research Institute, Urrbrae, SA: 113-32 (1984). Baldini, E. Italian experience of double curtain training systems with special reference to mechanisation. In: Webb, A.D., Ed. Grape and wine centen- Smart, R.E. Principles of grapevine canopy microclimate manipulation nial symposium proceedings; 18-21 June 1980; Davis, CA: University of with implications for yield and quality: a review. Am. J. Enol. Vitic. 36: 230-39 (1985a). California. Davis, CA: 195-200 (1982). Smart, R.E. Some aspects of climate, canopy microclimate, vine physiol- Bravdo, B., Hepner, Y., Loinger, C., Cohen, S. and Tabacman. H. Effect ogy and wine quality. In: Heatherbell, D.A., Lombard, P.B., Bodyfelt, of crop level on growth, yield and wine quality of a high yielding Carig- F.\'. and Price, S.F., Eds. Proceedings of the international symposium nane vineyard. Am. J. Enol. Vitic. 35: 247-52 (1984). on cool climate viticulture and enology; 25-28 June 1984; Eugene OR: Oregon State University Technical Publication 7628, Corvallis, OR. 1-19 Carbonneau. A., Casteran, P. and Le Clair, P.L. Essai de determination (1985b). en biologic de la plant entire, de relations essentielles entre le bioclimat naturel, Ia physiologic de la vigne et la composition du raisin. Ann. Smart, R.E., Robinson, J.B., Due, G.R. and Brien. C.J. Canopy microcli- Amelior. Plant 28: 195-221 (1978). mate modification for the cultivar Shiraz I. Definition of canopy microclimate. Vitis 24: 17-31 (1985). Carbonneau, A. Stress moderes sur feuillage induits par le systeme de conduite et regulation photosynthetique de la vigne. In: Bouard, J. and Smart, R.E. Canopy management to improve yield, fruit compositiion Pouget, R., Eds. Physiologic de la Vigne. Proceedings third symposium and vineyard mechanisation: a review. In: Lee, T.H., Ed. Proceedings of international sur la physiologic de la vigne; 24-27 June 1986; Bordeaux. the sixth Australian wine industry technical conference, 14-17 July 1986; France; Office International de la Vigne et du Vin, Pans, France: 378-85 Adelaide, SA: The Australian Wine Reseach Institute, Adelaide, SA: 205-11 (1987). (1987a).

Clingeleffer, P.R. and Possingham, J.V. The role of minimal pruning of Smart, R.E. The light quality environment of vineyards. In: Bouard. J. cordon trained vines (MPCT) in canopy management and its adoption and Pouget, R., Eds. Physiologic de la Vigne. Proceedings third sympo- in Australian viticulture. Aust. Grapegrower and Winemaker 280: 7-1i sium international sur la physiologic de la vigne; 24-27 June 1986; Bor- (1987). deaux, France; Office International de la Vigne et du Vin, Paris, France: 378-85 (1987b). Crawford, D.W. Economics of winegrape production on different trellis systems: a budgetary model approach. NI. Hort. Sci. thesis, Massey Univer- Smart, R.E. Influence of light on composition and quality of grapes. Acta sity (1987). Honiculturae 206: 37-47 (1987).

Khmer, M.W. Vineyard canopy management—a review. In: Webb, A.D., Smart, R.E., Dry, P.R. and Loftier, L. Critical relations of shoot spac- Ed. Grape and wine centennial symposium proceedings; 18-21 June 1980; ings in vineyards. In: Bouard, J. and Pouget, R., Eds. Physiologic de la Davis, CA: University of California, Davis, CA: 342-52 (1982). Vigne. Proceedings third symposium international sur la physiologic de la vigne; 24-27 June 1986; Bordeaux, France; Office International de Ia May, P. Trellising in relation to vine performance. In: Proceedings Second Vigne et du Vin, Paris, France: 378-85 (1987). Wine Industry Technical Conference; 7-9 August 1973; Tanunda. South Australia. Australian Wine Research Institute, Glen Osmond, South Aus- Soderlund, R., Orr, K., Gallagher, K., Porlet, D., and Harding, E. tralia (1973). Responses of Cabernet Sauvignon grapevines to lighter pruning. Aust. Grapegrower and Winemaker 280: 40-5 (1987). Remoue, M. and Lemaitre, C. Comparison de different densities de plan- tation et methodes de culture du sol (non culture et enherbement perma- Van den Ende, B. The Tatura trellis—a system of growing grapevines for nent). Conn. Vigne Vin 19: 197-206 (1985). early and high production. Am. J. Enol. Vitic. 35: 82-7 (1984).

Rotem, J. and Palti, J. Irrigation and plant diseases. Ann. Rev. Phytopath. 7: 267-88 (1969).

Shaulis, N.J., Amberg, H. and Crowe, D. Response of Concord grapes to light, exposure to Geneva double curtain training. Proc. Am. Soc. Hon. Sci. 89: 268-80 (1966).

Shaulis, N. and Smart, R. Grapevine canopies: management, microclimate and yield responses. In: Proceedings XIXth Int. Hort. Congress; 11.18 September 1974; Warsaw: vol. III: 254-65 (1974).

Shaulis, N.J. Responses of grapevines and grapes to spacing of and within canopies. In: Webb, A.D., Ed. Grape and wine centennial symposium proceedings; 18-21 June 1980; Davis, CA: University of California, Davis, CA: 353-61 (1982).

Proceeaings Secona international Cool Climate Viticulture ana Oenology Symposium. Auckland. New Zealand. January 1988. 72 JULY/AUGUST 2002 121

ous that the leaves are hot and stomates are closed, so the Yield limits for remaining leaves are not working efficiently. It is indeed naïve to assume that maximum stress gives maximum quality. Is it the lower yield or the mild stress which promotes vineyards - quality? Or maybe a combination of both? I think we must be very careful to separate these effects. It is my opinion that the mandated inefficiency? stress that causes lower yield is more likely to lead to higher quality than is the lower yield itself Did you hear the story about the grapegrower who walked into Let me clarify with an example: Imagine a vigorous a winery at crush and demanded that the enologist extract only Cabernet vineyard grown on. deep soil and carrying an eight- 100 gallons of wine from each ton of his grapes? To extract any ton per acre crop. Will quality be improved by thinning to four more, he said, would be to; compromise the wine quality tons per acre? I doubt it. More likely the vines will be put even I don't hear that story tali* but I have heard the follow- more out of balance, and the fruit probably even more shaded. ing one many times: AA. etiologist (or winery field rep) In this instance, I think the grower should be more con- walked into the vineyard kid asked that yield be lowered to cerned about affecting a modicum of stress at the right time, three tons per acre, when a gbt-ton per acre crop was hanging. rather than merely dropping fruit. In other words, the excess The higher yield, he said, would compromise wine quality. of shoot tips growing at veraison are more likely to damage quality than are a purported excess of grapes. Grape surplus — need for higher quality? or less fruit? Small berries, are they important? There are stories of large grape surpluses for the 2002 I also think the contribution of small berries to wine quality is harvest in California. This is particularly acute in the Central over emphasized. Certainly, a small berry has a larger surface- Valley for Cabernet Sauvignon, but each region will likely area-to-volume ratio, and so more skin to juice. But across the have problems. During my stay. at Cal Poly State University range of commercial berry sizes these changes are relatively small. (San Luis Obispo), I heard stories of problems (potential Researchers in Australia have made wine from large and surpluses) with Cabernet Sauvignon on the Central Coast. small berries within loads and found no difference in compo- The same was true for Australia,fpr the 2002 harvest, but an over- sition and quality. I think that it is the factors making berries all low volume vintage reduced the pressure towards the end. small that lead to quality, and not the small berries themselves. Not unexpectedly, at times of potential surplus, the pres- Small berries are a sign of stress. sure is on growers to. limit yields. I am eversure if the yield Water stress — especially before veraison — will cause limits are meantan to possibly improv quality or merely to smaller berries. Crop thinning at this time will cause larger, reduce the wineries' to tak fruit for which they not smaller berries. The easiest way to have small berries is may have no wine. market, " boo, by minimal pruning, but I believe that few enologists will In this column I want to review tkie situation, regarding endorse this practice! vineyard yield and wine quality. Some experimental results Vineyard yield and wine lity I have investigated the relationship between yield and The notion that low yield3g vineyards make better wine is quality in several experiments, in both hot and cold climates. quite widespread through4the world. I think it is European One of my first trials was with Syrah at Angle Vale in South in origin, and probably Fiench. The idep dates back to Roman Australia, a hot region like California's Central Valley. I com- times: "a struggling vine makes the best wine." Yield limits are pared a high yielding Geneva Double Curtain (GDC) to an defined under AOC appellation systems in France. open canopy with a "sprawl canopy" that was shaded. Many have questioned, however, whether quality can be The results were clear, and dramatic. The higher yielding imposed by legislation. The important issue to examine is GDC at 11 tons per acre produced wine with better color and whether low yields guarantee high quality. Does removal of phenols than did the sprawl at nine tons per acre. The respec- some fruit guarantee the remainder will have improved quality? tive sensory scores in a replicated tasting using wine industry In the remarks that follow, I will principally concern myself judges was 15.4 ex 20 and 11.9 ex 20. with red wines, though I believe that the same principles 4 have found similar trends in cool climates. As an example, generally apply to white'wines. . . a trial with 'Cabernet Franc in New Zealand showed that a It is my observation that many of the world's great red high. yielding, open canopy carrying 12 tons per acre made wines are grown with some stress. This is typically a water better wine than a shaded vertical shoot positioned (VSP) stress — enough to stop shoot growth before veraison and to trellis with six tons per acre. There was lower pH, more color, limit lateral leaf growth. I believe that, if the stress is mild, anthocyanins, and phenols for the higher yielding vines, and then there is only a small effect on yield. the sensory scores were 5.1 ex 7 for high yield and 3.5 ex 7 for However, a considerable amount of stress can greatly reduce low yield. yield, with 'a corresponding reduction in quality. I have seen I have seen other results with similar outcomes. For exam- severely4noisture-stressed vines struggling to ripen fruit. Some ple, many fruit thinning trials show little or no benefit on leaves have fallen off, and the remainder are yellow. It is obvi- fruit composition. 323 Balanced vines are important I believe that balanced vines make balanced wine. A balanced vine will have appropriate leaf area to ripen grapes, but not so much as to cause shading. Vme balance is achieved by using the correct trellis system and pruning level for the site, and maybe some other practices, such as irrigation management arid cover cropping, to produce a modicum of water stress.

Are there exceptions? In my experience there are some varieties that indeed seem yield-sensitive in relation to quality. The best example is Pinot Noir. I am unaware of any premium quality Pinot Noir being made from a moderate to high-yielding vineyard. It seems that this variety requires a larger than normal leaf-to- fruit ratio to produce quality wine. Pinot Noir seems as fussy about its yield as it is about where it is grown. There are a few other examples, typically with large berry and large clustered varieties like Zinfandel, Merlot, and Tempranillo. These varieties can set crops larger than they have leaf areas to ripen, so composition is improved by crop thinning.

The future I doubt that many winemakers will take seriously what I say above. Perceptions about yield and wine quality are deeply ingrained, and often repeated by wine writers. So growers can look forward to being requested to limit their efficiency (and income) by dropping crop while the market is tight. I do believe, however, that in 10 years things may be different. There will be more use of winery-based measures of grape composition and quality, as, for example, in grape color. New instruments using near infrared spectral analysis show great prOmise for real-time quality assessment during grape receiving at the winery. I also suspect that there will be more field trials looking at the relationship of yield to quality, especially looking at crop thinning. For the moment, I can offer winemakers a tip. Within any one region of similar climate, and for any given variety, the first vineyards to ripen often make the best wine. Harvest date can be a better indicator of quality than can yield. I think that more attention should be paid to irrigation practice and canopy management and vine balance, and less to yield. That will be to everyone's ultimate benefit. ■

Dr Richard Smart, "the flying vine-doctor," is an international viticultural consultant based in Australia. He ii also the Visiting Professor of Viticulture at Cal Poly; San Luis Obispo, CA. He can be contacted by e-mail at: [email protected] . Read about Dr. Smart's business including his consulting schedule, educational wine tours, and seminars at his home page http://www.smartvit.com.au