economics of vineyard design: vine and row spacing, …...wye lyre gdc table ii — grapevine...
TRANSCRIPT
These are dynamic times in the winegrape industry. Asdemand for high-qualitygrapes rapidly increases,many wineries and growers
are looking to expand production.Vineyard development is expensive,and available land for production ofhigh-quality grapes is limited.Successful expansion under these cir-cumstances requires careful planningand cost assessment.
In addition to soil preparation, scionvariety, and rootstock, vineyard designconsiderations are among the mostimportant decisions growers mustmake when optimizing current sites ordeveloping new vineyard sites.
Trellising and spacing between vinesand vine-rows influence fruit qualityand marketability. In addition, theydetermine vineyard development andoperational costs, the promptness ofreturn on investment, and the averagerate of return during the vineyard’slifetime.
Using production data from viticul-tural literature and a fictitious modelvineyard, we can evaluate expectedrate of return relative to initial vineyarddevelopment costs. Use the modelvineyard — which has a traditionalCalifornia winegrape-growing design— as a baseline for comparing otherpossible vineyard designs to determinewhich one will work best at your site.25
Vineyard modelThe model vineyard occupies 20
square acres (933.4 ft. per side) and is
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ECONOMICS OF VINEYARD DESIGN: Vine and row spacing, trellising
Stan Grant, Progressive Viticulture BY Figure 1 — Trellis systems by canopy and foliage-support type.
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planted with bench grafts in a vine androw spacing of 8-feet by 12-feet. Initialcost per acre for developing this modelvineyard is likely to be somewhathigher than the cost for developinglarger vineyards and somewhat lowerthan for smaller vineyards due to vari-ations in the ratio of number of rows torow length and number of end postsper acre.
Vines are bilateral cordon-trained ona T-trellis composed of 7-foot stakeswith 18-inch crossarms attached at thetop alternating with 5-foot stakes with-out crossarms. All stakes are T-stakesmade of 125- or 95-weight rail steel for7-foot and 5-foot lengths, respectively.Crossarms are 14-gauge steel. Endposts are 9-foot, recycled well stemswith a spade. Cordons are attached to asingle 12-gauge wire, and a 14-gaugewire on each end of the crossarm sup-ports the foliage. All wires are high-ten-sile, galvanized steel.
The model vineyard is drip irrigated.The drip hose includes in-line, pres-
sure-compensated, 0.5-GPH emittersthree feet apart. It is attached to a 14-gauge wire by “pigtail”-type clips atthree-foot intervals between the emit-ters. In this model, vineyard develop-ment costs other than trellis, irrigationsystem, vines, and planting are consid-ered constant.
Vineyard development costs used inthis economic analysis are those DuarteNursery incurred in 1997 and 1998while developing its vineyards in theLinden Hills area of San JoaquinCounty. The material costs (grapevines,trellis, and drip irrigation) are represen-tative of most of California. Labor costsused in the study are representative ofthe interior valleys and are lower thanin many coastal areas.
TrellisingIn the recent past, only a few trellis
types have been used to support wine-grape vines in California. Among thesimplest of these is the one-wire verti-cal trellis (Figure I). It consists of a sin-
gle wire fastened to the top of a stakeonto which cordons or canes aretrained and attached.
A T-trellis is more elaborate, and it isthe trellis of our model vineyard.Normally the T-trellis consists of somealternating pattern of short and tallstakes (e.g. one short, one tall) with acordon or cane wire fastened to thetops of the short stakes and to the sidesof the tall stakes (Figure I). At the top ofthe tall stakes a crossarm is attached,and wires are fastened to the ends ofthe crossarms to provide passive shootpositioning and foliage support.
While traditional trellis designs areoften still appropriate for many vine-yard applications, experimentation andexperience have shown that, undersome conditions, other types of trellis-ing can improve fruit yield and quality.
In cooler winegrape growing areas,the vertical shoot-positioned (VSP) trel-lis is used to invigorate shoots andassure buds and fruit are adequatelyexposed to sunlight. This trellis consists
1-wire vertical
T-trellis
VSP
Sylvos
2-wire divided
Wye
Lyre
GDC
Table I — Components of grapevine trellises included in a vineyard development economic analysis
Single
Single
Single
Single
Divided
Divided
Divided
Divided
None
Crossarm
Upward
Downward
None
Crossarm
Upward
Downward
0
0
50
0
0
0
50
0
Percent of stakesa
Shoot positioning
Canopy typeTrellis
0
50
0
0
0
50
0
0
100
50
0
50
100
50
50
100
5ft 6ft 7ft 8ft
Percent of crossarms
0
0
50
50
0
0
0
0
0
50
0
0
0
0
0
0
0
0
0
0
0
100
0
100
0
0
0
0
100
0
0
0
18in 24in 36in 42in
0
0
0
0
0
50
0
0
Lyreb
0
0
0
0
0
0
50
0
Fruit / cordon
12 gaugec
Stationaryfoilage
14 gauged
Moveablefoilage
14 gaugee
Number of wires per row
1
1
1
1
2
2
2
2
0
2
0
0
0
2
0
0
0
0
4
2
0
0
8
2
a Five ft. and 6 ft. stakes are 95 weight rail steel. Seven ft. and eight ft. are 125 weight rail steel and have spades.b Lyre crossarm formed from 125 T-stake material.c Wire clips required to attach wire to stake for single canopy trellises.d All trellis systems have one stationary wire clipped about 18 in. above the soil for attaching the drip hose.e Requires JR clips for shoot positioning wires on VSP and Lyre trellises.
of very short stakes and very tall stakesarranged in some alternating patternwith cordon or cane wires attached tothe tops of the short stakes and to thesides of the tall stakes as with the T-trel-lis (Figure I). Wire clips (usually two J-R type) or very short crossarms are fas-tened to the tall stakes at intervalsabove the cordon wire, and pairs ofwires are attached at each end of theclips or crossarms during the growingseason to position shoots into a verticalplane in line with the stakes.
Where sunlight is not too intenseduring the growing season but shootsgrow vigorously, vines are sometimesdevigorated by downward shoot posi-tioning. The Sylvoz or Hudson RiverUmbrella (HRU) trellis was designedfor this purpose. It is very similar to theone-wire vertical trellis with only a fewminor differences (Figure I).
First, the stakes are taller, so cordonsor canes are higher above the ground.This allows vertical space for the shootsbelow the cordon. Also every second orthird stake is taller still, so a pair ofwires may be temporarily attachednear its top and above the cordon dur-ing the early part of the growing sea-son. After the shoots are long enough,these wires are brought down on eitherside of the trellis, and the weight of thewires is used to hold the shoots down-ward. Sometimes the wires are attachedto a short crossarm.
Cordons or canes are the bearing sur-face of vineyards. That is, they are thelocation for both the apparatus for cap-turing sunlight and converting it intochemical energy (i.e. the leaves) and forthe products of the vines work (i.e. thefruit). The trellises described above allhave cordons in a single line within thevine row with the foliage forming a sin-gle canopy.
Many vineyard sites have the poten-tial to grow more leaves and producemore fruit than a single line of cordonswill allow. This potential can be real-ized by dividing or splitting the canopyto form two parallel bearing surfaceswithin the vine row. This is most easilyaccomplished by use of a crossarm with
wires on each end to support cordons.Either two or four cordons are trainedand attached on the wires. Typically,the vines within the rows of vineyardswith divided canopies are plantedmore closely together than vines withinthe rows of vineyards with singlecanopies to avoid overcropping of indi-vidual vines.
As with single canopies, the foliageof divided canopies may have no sup-port or may be positioned passively,vertically, or downward. The corre-sponding trellises for these types offoliage support or positioning are thetwo-wire divided, Wye, Lyre, andGeneva Double Curtain (GDC), respec-tively (Figure I).
Trellis costsParticular requirements of the site,
grape variety, mechanization, budget,winery and grower perceptions, andother factors affect trellis materials,design, and construction. However, inthe following economic analysis, thetrellises are designed to have as manyfeatures in common as possible, fullyrealizing that, for a few trellises, otherdesigns may be more common and lessexpensive. As each is discussed, we willalso examine some alternate design fea-
tures that can reduce the cost of moreelaborate trellises.
The T-trellis described in this modelvineyard is the base reference, and allother trellises in this economic modelhave been designed to be as similar to itas possible (Table I). Like the model T-trellis, all these trellises with foliagesupport (VSP, Wye, Lyre) have a foliagesupport apparatus on every otherstake. Metal T-stakes, which cost about9% more than wood (95 rail steel com-pared to 2 in. x 2 in. pressure-treatedDouglas fir), are used for all trellises.All cordon wires are 12-gauge steel,and all foliage-support wires are 14-gauge. J-R clips are used to hold foliagewires of the two trellises with verticalfoliage support (VSP and Lyre).
Eliminating the foliage support of theT-trellis to make a one-wire verticaltrellis reduces initial cost negligibly(Table II). Cost of the VSP and Sylvozare only about 10% more than the costof the T-trellis. The slightly higher costsof these trellises are due to additionalwires, clips, and tensioners and theirinstallation and to more expensivestakes. Since costs are similar for all ofthe single-canopy trellises, other fac-tors, such as extent of fruit exposureand adaptability to mechanization, are
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1-wire vertical
T-trellis
VSP
Sylvos
2-wire divided
Wye
Lyre
GDC
Table II — Grapevine trellis costs/acre. Trellis costs relative to T trellis costs, and relative trellis materials and labor costs.
2,084.
2,113.
2,268.
2,352.
4,528.
4,353.
7,603.
4,808.
99
100
107
111
214
206
360
228
Percent T-trellisCost/acre $Trellis
106
100
110
122
276
250
500
287
88
100
103
96
125
141
155
141
Total Materials Labor
Percent of total cost
64
59
61
65
76
72
82
75
36
41
39
35
24
28
18
25
Materials Labor
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more important and should determinewhich single-canopy trellis youchoose.
Cost for the two-wire divided, Wye,and GDC trellising are 206% to 228%more than for the T-trellis (Table II).Typically, the Wye system has foliagesupport on every third stake, whichwill reduce its cost relative to the T-trellis by an additional 10%.
Cost of the Lyre trellis in this analy-sis is 360% greater than the cost of theT-trellis, principally because of thehigh cost of the Lyre crossarms. Inpractice, the Lyre trellis is usually con-structed less expensively. Oftencrossarms are spaced further apart inthe row, for example, at every third orfourth vine. These arrangementsreduce Lyre trellis cost by 18% or 28%,respectively. The increased distanceresults in less fruit-wire support withinthe vine row and greater tension on theend posts. More elaborate end-postassemblies are usually required toaccommodate the added wire tension,which consumes about 2% or 3% of thesavings from further crossarm spacing.
Another cost-saving measure for theLyre trellis is the substitution of rebar(3⁄8-inch diameter) or some other metal
rod, wooden stick, or twine and anchorcombination for the stakes that do nothave crossarms. The rebar substitutionfurther reduces the trellis cost by 23%.These substitutions, which are alsosometimes used with the VSP trellis,decrease development costs substan-
tially, but Lyre trellis costs still remain30% to 70% more than Wye or GDCtrellis costs. Such modification alsolimits mechanical harvest methods tobow-rod harvesting, because the trelliswill not be sufficiently rigid for trunk-shaker harvesting.
While crossarms are the largestmaterial cost for the Lyre trellis, stakesare the largest material cost for othertrellises (Figure II). Excluding the Lyretrellis, stake costs range between 57%and 86% of the total trellis materialcosts. Crossarms, however, generallycomprise a large portion of the mate-rial costs of divided canopy trellises(60% for the Lyre and about 30% forthe others). End posts, wire, clips, andtensioners form a small portion of sin-gle-canopy trellis material costs and aneven smaller portion of divided-canopy trellis material costs.
End-post installation is the mostexpensive labor cost, accounting for45% to 78% of the total labor cost(Figure 3). The relative labor cost toinstall stakes is similar for all the trel-lises, but it is slightly more for divided-canopy compared to single-canopy trel-lises (about 15% and 21%, respectively).
Figure 3 — Relative labor costs for installing grapevine trellises
Figure 2 — Relative costs of grapevine trellis materials.
Crossarm installation accounts for12% to 19% of the cost of divided-canopy trellis installation, but it is onlya small part of T-trellis installation(about 5%). The cost to install wires,clips, and tensioners varies proportion-ately with their number and is least fortrellises with no foliage support (i.e.one-wire vertical and two-wiredivided) and most for trellises withupward shoot positioning (such as VSPand Lyre).
Returns on trellis investmentAlthough type of foliage support has
been shown to affect fruit yield,5 it isconsidered mainly a fruit quality factor,and therefore, assigning a monetaryvalue to it is difficult. Selection offoliage-support type usually dependson regional climate, perceived fruit-quality benefits, or grower or winerypreference rather than production eco-nomics.
Fruit perceived to be, or demonstratedto be, of superior quality due to foliagesupport is most easily marketed towineries and, consequently, has a defi-nite economic advantage for the grower.
A final economic considerationregarding foliage-support type involves
operational costs. Some elaborate trellis-ing may limit mechanization of somevineyard operations. For examplemechanical prepruning, which mayreduce pruning costs by 35% to 80%,4, 7, 14,
21 is currently not possible with mostLyre trellises because of horizontal sup-ports across the top of the crossarm.
Fruit quality can be enhanced bycanopy division, particularly if itdecreases shoot density and leaf layersin the fruit zone,20 but it is consideredprimarily a production factor. Underconditions of sufficient sunlight atmos-pheric heat, soil depth, soil moisture,and soil fertility, a divided-canopy trel-lis may yield up to 85% more fruit thana single canopy.5, 11, 15, 16, 17, 19 In addition,under these conditions a divided-canopy vineyard will produce largerquantities of fruit earlier in the vine-yard’s life than it would as a singlecanopy.
However, some operational costsinvolved with crop and foliage fordivided-canopy trellises will increasesubstantially, perhaps nearly doubling.The most prominent examples includehand operations such as pruning, shootthinning, and crop thinning. (Again,mechanical prepruning can help toreduce the cost of hand pruning.)
Still, in the majority of cases, theincremental returns from increasedfruit production from canopy divisionwill be much larger than the incremen-tal cost increases in vineyard develop-ment and operations. For example, aWye-trellis vineyard in a high-capacity
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Figure 4 — Effect of vine spacing on relative grape yield per vine.
Figure 5 — Effect of vine spacing on relative grape yield per acre.
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site will cost about 106% more per acreto develop (for trellis and training) andabout 10% more per acre to operate (forpruning, shoot thinning, and crop thin-ning) compared to the same vineyardwith a T-trellis, but it will generateabout 85% more revenue per acre.
Consider a T-trellis vineyard thatwould have yielded an average of sixtons per acre of $1,000 per ton grapes.Developing that vineyard with a Wyeinstead of our model T-trellis wouldresult in an increase in developmentand operational costs during the first 15years of about $4,390 per acre, but rev-enues over that period could increaseby about $63,750 per acre.
Vine SpacingUnless in-row vine spacings are
either extremely narrow or wide, theyusually have a much larger effect onyield per vine than they do on yield peracre (Figures 3 and 4). Therefore, theeconomics of established vineyards areusually not greatly affected by in-rowvine spacing.
There are, however, two exceptions.The contribution of each vine to theoverall vineyard yield increases with
more space between vines. As a result,missing vines have a greater impact onyield per acre and vineyard revenues invineyards with wider spacings thanwith narrower spacings. Missing vinesare of minor consequence for the vastmajority of vineyards. Wider-spacedvineyards have an additional disad-vantage, however. They normally comeinto production more slowly than nar-rower-spaced vineyards and, therefore,have a later return on investment22.
There are viticultural considerationsregarding vine spacing beyond yieldand rate of return. First, for any givenvariety, site, and set of managementpractices, excessive foliage and canopydensity are problems when the vinespacing is too narrow, and insufficientfoliage and overcropping are problemswhen the vine spacing is too wide.
Both of these extreme conditions aredetrimental to fruit yield and qualityand usually produce other undesirableside effects. They also result inincreased operational costs for extracanopy management (e.g. hedging andleaf removal) or extra water, fertilizer,and crop management (e.g. cluster thin-ning) for excessively narrow and wide
Figure 6 — Effect of vine spacing on variable vineyard development costs.
Figure 7— Effect of row spacing on relative grape yield.
vine spacing, respectively. Therefore,they should be avoided.
In California, the most common vinespacings for single-canopy trellisesrange from six feet to eight feet (recallthat eight feet is the vine spacing of ourmodel vineyard), although both nar-rower and wider spacings can easily befound. Frequently these same commonvine spacings are used in divided-canopy vineyards, but not always withsatisfactory results.
Some grapegrowers with divided-canopy vineyards spaced at six feet toeight feet find that their fruit ripenslater and is of lower quality than theirneighbors’ single-canopy vineyardswith similar vine spacing. These are theresults of overcropping, which can beavoided by using narrower vine spac-ings (four feet or five feet).
In the model vineyard, developmentcosts per acre decrease by $2,325 (from$5,234 to $2,909) as in-row vine spacingincreases from four feet to 10 feet(Figure 6). With more space betweenvines, the relative costs of vines, plant-ing, and trellising decrease, while thecost for drip irrigation remains con-stant. The rate of return during a vine-yard’s early years will have to exceedthe increased development cost of nar-rower spacing to make it the best eco-nomic alternative. This would only bepossible if early yields or crop value, orboth, were sufficiently high.
Row SpacingReducing the distance between rows
of vines from 12 feet to 10 feet to 8 feetincreases the number of rows persquare acre from 17 to 21 to 26, respec-tively. This relationship between rowsper acre and row spacing is nearly lin-ear with the number of rows per acreincreasing by about two for every footthe space between rows decreases.How narrow the spacing betweenrows can be is limited only by thewidth of available vineyard machin-ery.
There is a positive relationshipbetween the number of rows per acreand relative yield per acre (Figure 7).
Thus, row spacing is an importantvineyard production factor. There isno evidence that row spacing is a fruitquality factor. Given that rows per acreand vines per acre increase propor-tionately with narrowness of rowspacing, it follows that operationalcosts increase proportionately withnarrower spacing between rows.
Development costs for the modelvineyard also increase with decreasingspace between vine rows. Costsincrease by $1,700 per acre (from$3,350 per acre to $5,050 per acre)when decreasing space between vinerows from 12 feet to eight feet (Figure8). However, for all spacings betweenvine rows, the relative costs for vinesand planting (36%), trellis (40%), anddrip irrigation (24%) remained con-stant.
Relative yield and developmentcosts for different spacing betweenvine rows are roughly proportionate.That is, for the initial expenditure invineyard development with narrowerrow spacing, there is a return in grossrevenues that continues over the life-time of the vineyard and pays for itselfseveral times.
Relating vineyard design factorsVineyards are horticultural systems
with multiple design elements thatinfluence vine growth, fruit produc-tion, and fruit quality. These elementsalso influence development costs, oper-ational costs, and rate of return. Someof them are independent and others areinterrelated.
Because row spacing normally has anegligible influence on other vineyarddesign elements, it is an independentfactor. In-row vine spacing influencesthe extent of fruit- and foliage-bearingarea, while trellising affects the positionof the fruit and foliage bearing area inspace. It is the fruit- and foliage-bearingarea connection that relates vine spac-ing and trellising.
Costs of vine spacing and trellisingcan be evaluated together, using theinformation presented here. Start byselecting a trellis. In Table II find thecost of the trellis. Calculate the trelliscost relative to the T-trellis by dividingby 2,113. Find the development cost forthe vine spacing in Figure 6 and multi-ply it by the relative trellis cost quotientto obtain the cost estimate for vineyarddevelopment, less land preparation. ■
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Figure 8 — Effect of row spacing on variable vineyard development costs.
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References1. Anthony, B. R., and A. T. Richardson.
“Influence of vine spacing on growth, yield,fruit composition, and wine quality of Barberain the San Joaquin Valley.” In: Vine SpacingSymposium Proceedings. E. Weber (Ed.). pp. 87-91. Am. Soc. Enol & Vitic. (1999).
2. Archer, E., and H. C. Strauss. “The effectof vine spacing on vegetative growth andreproductive performance of Vitis vinifera L.(cv Pinot Noir).” S. Afr. J. Enol. Vitic. (1991).
3. Bioletti, F. T., and A. J. Winkler. “Densityand arrangement of vines.” Hilgardia. 8: 179-195 (1934).
4. Chesterfield, I. “Canopy management —New pruning and training systems forgrapevines.” Unpublished report. Dept. Agric.,Victoria.
5. Christensen, L. P. “Winegrape trellises forthe San Joaquin Valley.” Unpublished report.Univ. Calif. Coop. Ext.
6. Hedberg, P. R., and J. Raison. “The effectof vine spacing and trellising on yield and fruitquality of Shiraz grapevines.” Am. J. Enol. &Vitic. 33: 20-30 (1982).
7. Hollick, R. R. “Mechanical pruning ofvines in Australia.” In: Univ. Calif. Davis Grapeand Wine Centennial Symp. Proc. pp. 264-265.Univ. Calif. (1980).
8. Intrieri, C. “Experiences on the effect ofvine spacing and trellis-training system oncanopy micro-climate, vine performance, andgrape quality.” Acta Hortic. 206: 69-87 (1987).
9. Jensen, F., H. Andris, B. Beebe, and L.Bettiga. “The effects of row spacing, variety,and trellis on yields of three wine varieties.”
Unpublished report. Univ. Calif. Coop. Ext.10. Kliewer, W. M., J. Benz, and R. Johnson.
“Spacing, pruning, and trellising effects onyield.” Wines & Vines. Feb 1990, 32-33.
11. Kliewer, W. M. and R. E. Smart. “Canopymanipulation for optimizing vine microcli-mate, crop yield, and composition of grapes.”In: Manipulations of Fruiting. C. J. Wright (Ed).pp. 275-290. Butterworths, London (1989).
12. Klonsky, K., L Tourte, and C. Ingels.“Sample costs to produce organic wine grapesin the North Coast.” Univ. Calif. Coop. Ext.(1992).
13. Klonsky, K., B. Beede, P. Christensen, M.Costello, N. Dokoozlian, G. Leavitt, D. Luvisi,M. Norton, B. Peacock, and P. Livingston.“Sample costs to establish a vineyard and pro-duce wine grapes.” Univ. Calif. Coop. Ext.(1997).
14. Mitchell, T. G. “Vineyard mechanizationand its impact on production costs in theTaylor Wine Company vineyards.” In:Proceedings of the Second N. J. Shaulis GrapeSymposium: Pruning Mechanization and CropControl. pp. 66-68. Cornell Univ. (1993).
15. Morris, J. R., and D. L. Cawthon. “Effectof soil depth and in-row vine spacing on yieldand juice quality in a mature Concord vine-yard.” J. Am. Soc. Hort. Sci. 106: 318-320 (1981).
16. Reynolds, A. G., and D. A. Wardle.“Impact of training system and vine spacingon vine performance and berry composition onSeyval blanc.” Am. J. Enol. & Vitic. 45: 444-451(1994).
17. Reynolds, A. G., D. A. Wardle, and A. P.Naylor. “Impact of training system and vine
spacing on vine performance and berry com-position of Chancellor.” Am J. Enol. & Vitic. 46,88-97 (1995).
18. Reynolds, A. G., D. A. Wardle, and A. P.Naylor. “Impact of training system, vine spac-ing, and basal leaf removal on Riesling vineperformance, berry composition, canopymicroclimate, and vineyard labor require-ments.” Am. J. Enol. & Vitic. 47: 63-76 (1996).
19. Shaulis, N, H. Amberg, and D. Crowe.“Response of Concord grapes to light exposureand Geneva Double Curtain training.” Proc.Amer. Soc. Hort. Sci. 89: 268-80 (1966).
20. Smart, R., and M. Robinson. Sunlight intowine: A Handbook for Winegrape CanopyManagement. 88 pp. Winetitles, Adelaide(1991).
21. Verdegaal, P. S. “Mechanical and mini-mal pruning in winegrape production.” Reportmade to the San Joaquin Valley ViticultureTechnical Group, Jan. 13, 1993.
22. Westwood, M. N. Temperate-zone pomol-ogy: physiology and culture. 523 pp. TimberPress, Portland (1993).
23. Winkler, A. J. “The effect of vine spacingat Oakville on yields, fruit composition, andwine quality.” Am. J. Enol. & Vitic. 10: 39-43(1959).
24. Winkler, A. J. “Effect of vine spacing inan unirrigated vineyard on vine physiology,production, and wine quality.” Am. J. Enol. &Vitic. 20: 7-15 (1969).
25. Winkler, A. J., J. A. Cook, W. M. Kliewer,and L. A. Lider. General Viticulture. 710 pp.University of California, Berkeley (1974).
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