Terroir Influence on Water Status and Nitrogen Status of non-Irrigated
Cabernet Sauvignon (Vitis vinifera). Vegetative Development, Must and
Wine Composition (Example of a Medoc Top Estate Vineyard, Saint Julien
Area, Bordeaux, 1997)
X. Chone1-2, C. Van Leeuwen1'2, P. Chery2 and P. Ribereau-Gayon1
1) Faculte d'Oenologie de Bordeaux, Universite Bordeaux 2 Victor Segalen, 351 Crs de la Liberation, 33405 Talence Cedex, France
2) ENITA de Bordeaux, 1 Crs du General de Gaulle, 33175 Gradignan Cedex, France
Submitted for publication: March 2000
Accepted for publication: January 2001
Key words: Terroir, Nitrogen, water status, Vitis vinifera, Cabernet Sauvignon, vigour, anthocyanin, phenolic content, must nitrogen
content, leaf water potential
Terroir effect on vine vigour, must composition and wine quality was investigated for Cabernet Sauvignon during
a rainy vintage in a top estate of the Medoc area (Bordeaux, France). Soil was the only variable in this survey. Vine
water status was determined by means of leaf water potential. Mild water deficits were observed only on a gravelly
soil with a shallow root zone. Vine nitrogen status was determined by total must nitrogen content. Nitrogen status
varied from deficient to unlimited. Nitrogen deficiency reduced vine vigour to a greater extent than did mild water
deficits. The smallest berries, as well as the highest phenolic content for both must and wine, were observed under
nitrogen deficiency. Both early mild water deficits and a nitrogen deficiency throughout the growth period were
demonstrated to have beneficial effects on the phenolic content of berries and on wine quality. Two combinations
of vine water status and vine nitrogen status led to the most highly appreciated wines: a low nitrogen status without
water deficits and a medium nitrogen status accompanied by mild water deficits.
For any given vineyard terroir can be described as the combination of pedoclimatic conditions, vine components such as cultivar, clone and rootstock as well as viticultural techniques (pruning system, canopy management, etc.). Given this, terroir must be
seen as a complex system with multiple variables: it is impossible to study all the variables in one experiment. Within a single
estate (10 to 100 ha) in Bordeaux, there is generally no climatic
variation but several types of soil. It is well known that the effect
of the soil on vine behaviour is mediated through varying watercontent levels and their effects on vine water status (Seguin,
1970; Seguin, 1986; Van Leeuwen & Seguin, 1994). Water
deficits occur when transpiration exceeds the ability of the root
system to supply water to the transpiring leaves. Mild water
deficits are known to have positive effects on reducing berry size
(Smart, 1974) and on berry skin anthocyanin and tannin content
in red grape varieties (Matthews & Anderson, 1988; Van
Leeuwen & Seguin, 1994; Koundouras et al, 1999). Schultz and
Matthews (1993) observed that in potted vines water deficits
caused embolism in the xylem shoot apex, which stopped shoot
growth. This has been confirmed in field studies (Matthews et al,
1987; Van Leeuwen & Seguin, 1994; Naor & Wample, 1996).
Given this consideration, it can be said that under mild water
deficits vegetative growth is no longer in competition with reproductive development as a sink of photosynthesis resources. Hence
fruits are primary sinks. This can partly explain the richer must
and wine constitution obtained from vines having undergone mild
water deficits.
Without the addition of nitrogen fertiliser, vine nitrogen status
depends upon soil organic matter content, its mineralisation rate
and the C/N ratio. It has been shown for Merlot (Delas et al,
1991) and for Thompson seedless and White Riesling (Kliewer
and Cook, 1971; Spayd et al, 1994) that nitrogen fertilisation
increases vigour.
In the Bordeaux oceanic climate rainfall can vary to a considerable extent from one season to another. In a dry season, such as
1990, high enological berry potential and therefore wine quality
are strongly linked to mild water deficits (Van Leeuwen and
Seguin, 1994). In a rainy season, this is less likely to occur even
though a soil effect on wine quality is generally admitted to exist
despite the rainy conditions. As a better understanding of the terroir effect can help growers in their vineyard management and
grape selection, the effect of soil variation on vine vigour, berry
constitution and wine quality was investigated in this survey during a rainy vintage. Vine water status and vine nitrogen status
were measured by means of physiological indicators. In the case
studied soil was the only variable differentiating blocks planted
with the same cultivar and rootstock and with the same vine spacing and subject to the same canopy management. Conradie
(1986) demonstrated that vine nitrogen uptake from bud break
through fruit maturity is progressively less utilised for vegetative
growth and increasingly more utilised by the fruit. This was confirmed by Soyer et al (1995), who showed that vine berry nitrogen content closely reflected mineral nitrogen availability in the
soil. Thus, berry total nitrogen content can be used as a physiological indicator of vine nitrogen status. However, the levels of
total nitrogen berry content as an indicator of vine nitrogen status
is poorly documented.
MATERIALS AND METHODS
Experimental location and plant material
The study was conducted in Leoville Las Cases vineyard. SaintJulien, Haut-Medoc, Bordeaux area, France. Soil mapping of this
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
Terroir Influence on Waier and Nitrogen Status of Cabernet Sauvignon
vineyard revealed an unexpected soil variation: nine pedological
types spread over only 100 ha. Four blocks planted with Vitis
vinifera cv. Cabernet Sauvignon grafted on Vitis riparia L. root-
stock were studied. Vine age was between 24 and 31 years. The
four blocks were identified as 1G, 3 A, 4H and 5P. Each block was
set up on a different soil type. To avoid soil variation inside a
block, only 100 vines were studied per site, all located around the
soil pit studied. The soil type, texture, percentage of organic matter in fine soil, occurrence of water table and root zone depth are
presented in Table 1.
The four blocks were less than 500 m apart. The altitude of the
four blocks varied from 10 to 20 m and row orientation was identical. Hence it was accepted that no climatic variation occurred
among the four blocks. This was confirmed by the vine phenology in 1997, which was similar for all the terroirs studied (bloom:
May 25; veraison: July 21). The vines were spaced 1 x 1.1 m
apart and double Guyot pruned; trunk height was 0,4 m from the
soil surface. During vegetative development, vine canopy was
mechanically cut at 1.1 m height for every block.
Water potentials
Pre-dawn leaf water potential (dawn^) and leaf water potential
(leaTf) were measured with a pressure chamber (Scholander et
al, 1965) equipped with a digital manometer (SAM Precis 2000,
33175 Gradignan, France). DawnY was measured at the end of
the night on uncovered mature leaves. LeaPf was measured on
mature leaves exposed to sunlight, whether they were transpiring
or not (Turner, 1981).
Nitrogen status
As in the preceding years, no nitrogen fertiliser was added in
1997. Hence vine nitrogen uptake resulted mainly from mineralisation of organic matter. Vine nitrogen uptake was estimated
weekly, from veraison through harvest, by the berry total nitrogen
content (Bell et al, 1979).
Vine vigour
Dry leaf mass was measured on eight vines per terroir just before
harvest. Leaf area per vine was deduced from the correlation
obtained. Average total bunch mass per vine was measured on 30
vines per block on the day of harvest. Average pruning mass per
vine was determined on 25 vines per block.
Must characteristics from veraison through harvest
From veraison through harvest one thousand berries were sampled weekly at random from 100 vines on each site. These berries
were immediately counted and weighed to determine average
fresh berry mass. Berries were pressed and the juice was gently
centrifuged to remove suspended solids. Sugar content was measured by refractometry. Titratable acidity was measured manually with Bromothymol blue. The titration was done with 0.1 N
NaOH to an end point of pH 7.0. Malic acid was determined
using an enzymatic kit from Boehringer Mannheim.
On 200 berries anthocyanins were determined by the method of
Ribereau-Gayon & Stonestreet (1965). The measurement of
absorbency was conducted at a wavelength of 520 nm (optical
distance: 1 cm). Tannins were measured by the 1PT: "indice des
polyphenols totaux" (Ribereau-Gayon, 1970). The wavelength
used was 280 nm (optical distance: 1 cm).
Micro vinifi cation
Microvinification was conducted identically for all lots. For every
terroir 50 kg of fruit were harvested on the same day (September
27). The fruit from each block was crushed and stems were
removed. For every lot 40 kg were put into a SOL stainless steel
tank. In order to have similar wine alcohol content for tasting, 1G,
3A and 5P must were chaptalised to obtain the same sugar content as found in 4H. Alcoholic fermentation and malolactic fermentation were enhanced with a selected yeast strain and a selected bacteria strain, respectively. All the wine-making parameters
(fermentation arrd maceration temperature, pumping over frequency, draining away, etc.) were similar.
Wine tasting
Wines were tasted blindly by a panel of 15 professional tasters.
They were noted by positive preference order from 1 to 4. The
scores of all judges for a wine were summed. Least significant
difference (LSD) was determined by a modified Chi2.
Statistics
Water potential and vigour indicators data were analysed with the
ANOVA procedure and the Newman Keuls test to determine least
significant difference (Statbox Pro Software).
RESULTS
Water status
Soil water content was at a field capacity on all the soils studied
in the spring (April), which is usual in the French oceanic area. In
the Medoc 1997 was a rainy vintage: the rainfall in May, June and
August was far above the average calculated over a 39-year span.
Conversely, rainfall was a bit less than average in July and
September (Table 2). From bloom through veraison total rainfall
TABLE 1
Soil and rooting characteristics of the studied plots.
Type of soil
Gravel content
Water table
Texture of fine soil in limits
of root zone depth
Organic matter (% in fine
soil) in the top 60 cm
Root zone depth (meter)
1G
3A
4H
5P
Neoluvisol on
gravely soil
75%
Redoxisol with heavy
clay subsoil
50%
Podzosols
no
Planosol sedimorphe with
heavy clay subsoil
15%
no
yes
15%
no
Sandy clay
Heavy clay
Sandy clay
Sandy
1.5
1.2
1.5
0.5
0.7
2
2
1
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
lerroir influence on Water and Nitrogen Status oj l^atternel bauvignon
20
TABLE 2
Monthly rainfall in Saint Julien in 1997, compared with the longterm average.
Rainfall
1997 (mm)
Average rainfall
1961-1990 (mm)
May
June
July
August
September
158.4
146.6
36
80
32.2
77.3
56.2
46.5
54.2
74.1
was 18 mm and from veraison to harvest 113 mm. From July
through September 1997 5P dawnT data varied from -0.10 to 0.17 MPa, whereas over the same period IG dawn¥ data varied
from -0.12 to -0.30 MPa (Fig. 1). At three different stages (July,
August and September), dawn*F data were significantly lower for
IG than for the other blocks.
On August 23 midday leaf water potential showed no differences among the 4 soils (Fig. 2). Yet IG leaf water potential was
significantly more negative than that of the other locations at the
end of the afternoon, being the beginning of the recovery period
of vine water status. This confirmed the lower pre-dawn leaf
water potential measured on IG during the same period. Climatic
conditions were identical for the four blocks studied. Thus water
status differences observed in 1997 reflected mostly soil ability to
supply water to the vine. Hardie & Considine (1976) and Van
Leeuwen et al (1994), showed that dawnY of -0.30 MPa reflected a mild water deficit, which induced slackening of shoot
growth. Given this, IG can be considered as the only block where
vines underwent mild water deficits in 1997.
As IG received as much rainfall as 5P, where no water deficit
occurred, IG water deficits reflected low water-storage capacity,
due to a high proportion of gravel in the shallow root zone (Table
1). Conversely, on 5P the root zone was twofold deeper than on
IG, whereas the gravel content in the root zone was fivefold
lower. These conditions were reflected in the high dawnT data
collected from July to September on 5P. On 4H, despite the shal-
low root zone, no water deficits were detected. This was due to a
permanent water table linked to the subsoil clay depression.
Conversely, on 3A the subsoil clay is convex. Thus no water table
can be formed ant the root zone is deeper (Table 1).
Nitrogen status
From veraison through harvest, berry total nitrogen content for
4H was threefold lower than for 5P and twofold lower than for IG
(Fig. 3). Berry total nitrogen content of 3A was between that of
4H and of IG. Throughout this period the difference between
berry total nitrogen content appeared to remain constant from one
block to another.
Lower total nitrogen content for 4H reflected the low organic
matter content in this soil (Table 1). Conversely, 5P soil organic
matter percentage was fourfold higher than for 4H, with total
berry nitrogen being threefold higher than for 4H. Thus, under the
conditions of this survey, berry total nitrogen content appeared to
reflect soil organic matter content closely.
Vine vigour
A strong correlation between leaf area (measured with a planimeter) and dry leaf mass was established. Total leaf area per vine
(Table 3) was not significantly different for IG, 3A and 4H, indicating that total leaf area per vine was not affected by water status for these 3 blocks. Hence, IG mild water deficits were only
due to low soil-water content available in the root zone depth.
Moreover, significantly larger total leaf area per vine did not
enhance water deficits on 5P. This confirmed the higher soilwater content in the root zone depth of 5P.
The significantly lower total leaf area per vine for 4H, in comparison to 5P was not due to water status, which was similar for
both terroirs. The lower vine nitrogen status on 4H appeared to
explain its weaker vigour. Furthermore, the total pruning mass
per vine and the total cluster mass per vine were also significantly lower on 4H than on 5P.
As with total leaf area per vine, 4H and IG showed no significant difference for total pruning mass per vine, nor for total leaf
area per vine. Two vigour indicators, total bunch mass per vine
-0,2--
(0
Q)
-0,25
-0,35
JULY
AUGUST
SEPTEMBER
FIGURE 1
Dawn leaf water potential evolution from July through September 1997, Data are means of 8 measurements on 8 adjacent vines.
Error bars indicate SE.
S. Afr. J. EnoL Vitic., Vol. 22, No. 1, 2001
Termir Influence an Water and Nitrogen Status of Cabeme! Saavignon
II
0,0
d)
« -1,0
-o~ 1G leaf water potential
-•- 3A leaf water potential
-D-4H leaf water potential
-*c— 5P leaf water potential
-1,6
02:24
03:36
04:48
06:00
07:12
08:24
09:36
10:48
12:00
13:12
14:24
15:36
16:48
18:00
19:12
FIGURE 2
Diurnal leaf water potential on August 23, 1997. Data are means of 8 measurements on 8 adjacent vines. Error bars indicate SE.
360 - •
330-•
300-270 -j"
f
240-
210-180-150-120 90-SEPTEMBER
FIGURES
Berry total nitrogen content from veraison through harvest (1997).
TABLE 3
Vigour indicators: Total leaf area, total pruning mass and total
bunch mass per vine.
1G
3A
4H
5P
Total leaf area per
vine (m2)
1.01 a'1)
0.96 a
0.8 a
1.46 a
Total pruning mass
per vine (kg)
Total bunch mass
0.24 a b
0.31 b
0,19 a
0.43 c
per vine (kg)
0.935 a b
1.09b
0.765 a
1.103b
(') Values within rows followed by the same letter do not differ significantly.
and total shoot mass per vine, showed that 3A was significantly
more vigorous than 4H, but no more than 1G. Thus the difference
in nitrogen supply between 3A and 4H, which had the same water
status, seemed to have had more influence on vigour than did vari
ations in water status between 1G and 4H or between 1G and 3A
Total leaf area per vine and total pruning mass per vine for 51
were significantly higher than for the 3 other terroirs, while 51
total cluster mass was significantly higher than 4H only. As tht
trellising and pruning system were the same on the four sites, thii
showed that low nitrogen status on 4H reduced total bunch mas:
per vine to a greater extent than did the mild water deficits on 1G
This further emphasised that low vine nitrogen status had ;
greater influence on vigour than did mild water deficits befort
veraison.
Fresh berry mass
From veraison through harvest 5P fresh berry mass was constant
ly 30% higher than that of 4H, whereas it was only 10% to 15 9i
higher than that of 1G and 3A (Fig. 4). Fresh berry mass and tota
cluster mass per vine showed a strong linear correlation (R2=0.92
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
Terroir Influence on Water and Nitrogen Slalus of Cabeme! Sauvignon
12
160
150
3A
140
-1G
-4H
-5P
70 - •
60
AUGUST
SEPTEMBER
FIGURE 4
Fresh berry mass evolution from veraison through harvest (1997).
230 y-
220 - •
210-200 - •
190 -180 -•
170 -160 150 -•
140-•
130 -•
120-•
110-100 - 90-
AUGUST
SEPTEMBER
FIGURES
Must-reducing sugar content evolution from veraison through harvest (1997).
440,0
•3Q>
JULY
AUGUST
SEPTEMBER
FIGURE 6
Must titrable acidity evolution from veraison through harvest (1997).
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
Terroir Influence on Water and Nitrogen Status of Cabernet Sauvignon
13
SEPTEMBER
FIGURE?
Must malic acid (meq/L) content evolution from two weeks post-veraison
through harvest (1997).
1400
1300— 1200 -
1 "'
3A
1G
C
700 - -
600-•
500
400
AUGUST
SEPTEMBER
FIGURES
Must anthocyanin content evolution from two weeks after veraison through
harvest (1997).
n=4), which demonstrated that flower abortion did not explain the
yield difference between the sites.
Low fresh berry mass on 4H confirmed the low vigour previously observed. Lower fresh berry mass on 1G and 3 A, compared
to 5P, can be attributed to mild water deficits and lower nitrogen
status respectively, even though these are not reflected by significant differences in total cluster mass per vine.
Berry composition through ripening
Must from 4H and 1G exhibited the highest sugar content and the
lowest acidity, whereas the reverse was true on 5P (Figs. 5, 6 and
7). Must sugar content was less for 1G than for 4H. Even though
titratable acidity on 1G and 4H was similar, malic acid content
was nevertheless lower on 1G. As already shown by Van Leeuwen
and Seguin (1994), vine water deficits enhance low must malic
acid content. For the four sites a strong linear correlation
(R2=0.97; n=4) between average dawn*JK data (from July through
September) and berry malic acid content at the harvest was
observed.
Anthocyanins, tannins and wine appreciation
Anthocyanin content for 4H was almost twofold higher than for 3A
and 5P, whereas the difference between 4H and 1G was less pronounced (Fig. 8). IPT differences followed the same hierarchy,
with 4H and 1G exhibiting the highest tannin content (Table 4).
The professional panel of tasters distinguished 4H and 1G as the
best wines (Table 4). The most appreciated wines were also the
highest in phenolic content. Wine phenolic content correlated
closely with phenolic content (Table 4). Must phenolic content for
3A, 4H and 5P suggested that low nitrogen status without water
deficits was linked to high enological potential for a red grape vari-
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
TABLE 4
Must phenolic content at the harvest, wine phenolic content and
wine-tasting appreciation.
3A
4H
5P
823
1180
748
33
29.8
36.5
611
54
463
730
50
70
401
43
50.5a(2)
39 b
58 a
21 c
1G
Must anthocyanin content
at harvest (mg/L)
Must tannin content at
harvest (IPT) (1)
Wine anthoeyanin
content (mg/L)
Wine tannin content (IPT)
Wine-tasting sum rate
(i) IPT = "indice des polyphenols totaux".
<2> Values within rows followed by the same letter do not differ significantly.
ety such as Cabernet Sauvignon. This confirmed the result of
Keller and Hrazdina (1998) on continuously irrigated, potted
Cabernet Sauvignon. They observed that excessive nitrogen fertilisation decreased win phenolic content. In a rootstock trial Delas et
al. (1991) observed an increase of phenolic grape content for some
of the rootstocks where nitrogen fertilisation was not applied.
Hence, both early mild water deficits and lower nitrogen status
throughout the growth period had beneficial effects on total berry
phenolic contents and wine quality. This appeared to be linked to
the limiting effect on the vine vigour of both of these factors.
DISCUSSION
With the same water status for both sites, lower nitrogen status on
4H than on 5P induced a decrease in vigour. The total leaf area
per vine, the total pruning shoot mass per vine and the total cluster mass per vine were respectively 55%, 44% and 30% lower on
4H than on 5P. Considering these vigour indicators, 4H underwent a clear nitrogen deficiency in 1997. The total cluster mass
per vine represented a calculated yield of 6.5 tons per ha for 4H,
suggesting that nitrogen deficiency level was moderate, as it
allowed an acceptable yield for a high-quality wine-producing
vineyard.
Bell et al (1979) reported on continuously irrigated Thompson
seedless that for a total nitrogen content of must at harvest ranging from 287 to 754 mg/L no significant difference occurred in
crop mass per vine. Kliewer and Cook (1971) showed on potted
vines that leaf area and trunk circumference increased linearly
with increasing concentrations of nutrient solutions ranging from
0 to 4 mM of NOs, whereas they remained constant with concentrations ranging from 4 to 8 mM of NOs. This suggests that the
Bell et al (1979) range of must total nitrogen content indicated no
lack of nitrogen, because it was superior to the threshold value
where nitrogen begins to have an effect on vigour. In 1997 5P
must total nitrogen content (290 to 370 mg/L from veraison
through harvest) fell within this range. Given this, 5P must total
nitrogen data reflected no limiting vine nitrogen status. Moreover,
3A must total nitrogen content (185 to 230 mg/L) corresponded
to an intermediate level of vine nitrogen status, between those of
5P and of 4H. This was emphasised by the fact that 3A vigour,
estimated by the total pruning mass per vine and the total cluster
mass per vine, was significantly lower than that of 5P and significantly higher than that of 4H, with no water status difference.
Conradie (1980, 1986) demonstrated that most of the vine nitrogen uptake occurs from bud burst through veraison. During this
period nitrogen is increasingly allocated to fruit. From veraison
through harvest Conradie (1991) observed a translocation on
Chenin blanc of nitrogen from shoot, leaves and permanent structure to bunches. These observations were confirmed by constant or
slightly increasing must total nitrogen content on the 4 sites in 1997,
from veraison through harvest, despite different rates of berry diameter increase (Figs. 3 and 4). Low nitrogen status for 4h can thus be
considered as reflecting limited vine nitrogen uptake since bud
break. This could explain why the low nitrogen status of 4H reduced
vigour more than did 1G mild water deficits for 1G. 4H low nitrogen status was constant through the vegetative and the reproductive
periods (Fig. 3), whereas 1G mild water deficits appeared at the end
of fruit set and were not permanent until harvest (Fig. 1).
Further investigations will be necessary to define more accurately the range of total nitrogen content in must leading to the
best must and wine quality. Different total nitrogen contents data
on 1G and 4H indicated that a nitrogen status varying from low
to medium favoured the production of highly appreciated wine in
this Bordeaux top estate. Yet 1G and 3A grape total nitrogen content data suggested that a medium nitrogen status was adequate to
obtain a high-quality wine, if associated with mild vine water
deficits. Conversely, under the conditions of this survey, without
vine water deficits only nitrogen deficiency on 4H (90 to 150
mg/L of total must nitrogen) had an obvious positive effect on
must and wine phenolic content. This positive effect on wine
quality suggested that nitrogen deficiency should be maintained
in the vineyard and that nitrogen deficiency in must should be
corrected in the tank before and/or during the fermentation
process. This practice is already followed with success in several
Bordeaux vineyard areas.
CONCLUSIONS
This terroir survey, carried out during a rainy season in the
Bordeaux area, revealed a soil effect on vine nitrogen status measured by must total nitrogen content. Despite the rainy vintage, we
observed on a gravelly soil (1G) mild water deficits linked to low
soil water content in the shallow root zone. Low nitrogen status
was found on soil having a particularly low organic matter content
(4H). We observed that low nitrogen status reduced vine vigour
more than did mild water deficits. Yet when vines were subject to
one of these limiting factors, the wines produced in this Bordeaux
top estate were of significantly higher quality. Low vine nitrogen
status induced high berry tannin and anthocyanin content, accompanied by low berry mass. It also reduced yield, but this may be
acceptable in a very high-quality grape-producing vineyard.
Considering the benefits of low vine nitrogen status on the phenolic content of must and wine, it remains to define how this low
nitrogen status can be managed more accurately in order to conserve the equilibrium between the highest possible wine quality
and a decreased but economically acceptable yield.
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Soyer, J.P., Molot, C., Bertrand, A., Gazeau, O., Lovelle, B.R. & Delas, J., 1996.
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Bordeaux. Tec Doc ed., Paris. 81-84.
Matthews, M.A., Anderson, M.M. & Schultz, H.R., 1987. Phenologic and growth
responses to early and late season water deficit in Cabernet franc. Vitis 26,
147-160.
Spayd, S.E., Wample, R., Evans, R.G., Stevens, R.G., Seymour, B.J. &Nagel,
C.W., 1994. Nitrogen fertilisation of white Riesling grapes in Washington. Must
and wine composition. Am. J. Enol. Vitic. 45, 31-41.
Matthews, M.A. & Anderson, M.M., 1988. Fruit ripening in Vitis vinifera L.:
Responses to seasonal water deficits. Am. J. Enol. Vitic, 39, 313-320.
Turner, N.C., 1981. Techniques and experimental approaches for the measurement
of plant water status. Plant Soil 58, 339-336.
Naor, A. & Wample, R.L., 1996. Diurnal internode growth rate in field-grown
'Concord' (Vitis labrusca) grapevines. J. Hortic. Sci. 71, 167-171,
Ribereau-Gayon, P., 1970. Le dosage des composes phenoliques totaux dans les
vins rouges. Chim. Anal. 52, 627-631.
Van Leeuwen, C. & Seguin, G., 1994. Incidences de I'alimentation en eau de la
vigne, appreciee par 1'etat hydrique du feuillage, sur le developpement de 1'appareil vegetatif et la maturation du raisin (Vitis vinifera L. cv. Cabernet franc,
Saint Emilion, 1990). J. Inter. Vigne Vin. 28,'81-100.
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
Relationship Between Microclimatic Data, Aroma Component
Concentrations and Wine Quality Parameters in the Prediction
of Sauvignon blanc Wine Quality
J. Marais1, F. Calitz2 and P. D. Haasbroek3
1) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa
2) ARC Biometry Unit, Private Bag X5013, 7599 Stellenbosch, South Africa
3) ARC Agromet, Private Bag X5013, 7599 Stellenbosch, South Africa
Submitted for publication: September 2000
Accepted for publication: April 2001
Key words: Microclimate, temperature, radiation, Sauvignon blanc quality, prediction model
Sauvignon blanc grape chemical and wine sensory data, as well as meteorological data (temperature and visible light
radiation), collected in three climatically different wine regions in South Africa over three seasons and from two
different canopy treatments were statistically analysed. A model for the prediction and/or definition of Sauvignon
blanc wine quality was developed. The model utilises above- and within-canopy radiation and can explain 68.8% of
the variation in the cultivar-typical vegetative/asparagus/green pepper intensity of Sauvignon blanc wine. Other
significant correlations, e.g. between temperature and monoterpene concentrations, were also obtained. Further
research is necessary to test and refine this model for application under different environmental conditions.
Over many years research has been aimed at developing a simple
model or recipe that could define and predict wine quality.
Examples are sugar/acid ratio (°B/TTA) (Du Plessis & Van
Rooyen, 1982), the glycosyl-glucose (G-G) assay (Francis et al,
1998) and the red wine colour index (Holgate, 2000). Such a
model should also be useful as a method to compensate the grape
producer according to grape quality. The aim further is that the
model should incorporate parameters that are easily measurable
under field conditions, instead of parameters such as aroma
impact volatiles, the quantification of which is dependent on
complicated and expensive gas chromatographic and mass spectrometric analyses. Due to the complexity of factors affecting
grape and wine composition and quality, attempts to date have
achieved varying degrees of success and a foolproof, simple
model still has to be developed. Nevertheless-, earlier attempts
were valuable and all contribute something to the eventual solution of this problem.
The purpose of this study was to correlate microclimatic data
(temperature and radiation) with aroma component concentrations and wine quality parameters of Sauvignon blanc and to
develop a model for predicting wine quality.
MATERIALS AND METHODS
Grapes, regions and seasons
Vitis vinifera L. cv. Sauvignon blanc grapes, grown in three climatically different regions, namely Robertson (Region IV, 1945 2222 degree days), Stellenbosch (Region IE, 1668 -1944 degree
days ) and Elgin (Region II, 1389 - 1667 degree days) (Le Roux,
1974), were used. A single canopy manipulation treatment, which
altered microclimate in a natural way to obtain a higher degree of
shading, was applied in each region (Archer & Strauss, 1989;
Marais, Hunter & Haasbroek, 1999). Control vines were not
manipulated. Three replications, consisting of 15 vines per replica, were used. The general viticultural practices followed were
described by Marais et al. (1999). Grapes were obtained over
three seasons, namely 1997, 1998 and 1999. Results of the 1997
and 1998 seasons were published by Marais et al. (1999) and trials during the 1999 season were a repetition of the first two seasons.
Grape samples (whole bunches, 2kg per sample) were collected weekly at random from each treatment and replicate over three
weeks between approximately 16°B (close to veraison) and 21°B
(ripeness). Grapes were harvested at ripeness (fourth ripening
stage) for wine production, following standard Nietvoorbij practices for small-scale white wine production (Marais et al., 1999).
Meso- and microclimatic measurements
MCS data loggers, which continually measured temperature and
visible light radiation (300-1200nm) over the whole ripening
period on an hourly basis, were installed within selected vine
canopies in the vicinity of the clusters, as well as above the
canopies. Each radiation sensor consisted of 10 individual sensors, fitted in parallel onto a metre-long rod, thus giving a more
Significant correlations between microclimatic parameters and
wine sensory characteristics were reported earlier (Noble, ElliotFisk & Alien, 1995). Models using light radiation in the prediction of photosynthesis under field conditions, were also developed (Blackburn & Proctor, 1983; Goudriaan, 1986; Spitters,
1986; Haasbroek, Myburgh & Hunter, 1997). Photosynthesis is
dependent on light radiation and temperature and is indirectly an
important factor in grape composition development.
The approach in this study was to investigate the possible use
of microclimatic parameters as a quality predictor, which can be
easily measured over the whole grape-ripening period. The rate of
enzymatic and chemical reactions in grapes, in terms of development and/or degradation of components, is dependent mainly on
temperature and light radiation. Therefore these two climatic
parameters were used as variables. Canopy density, which is a
function of different climatic and viticultural factors, largely
determines the effects of temperature and light radiation.
S. Afr. J. Enol. Vitic., Vol. 22, No. 1,2001
22
A Model for Predicting Sauvignon blanc Wine Quality
reliable average reading within the canopy (Marais et a/., 1996;
1999). These measurements were done in each experimental unit.
Aroma component analyses
Grape samples from each treatment, region, season and replicate
were analysed for free and bound monoterpenes and bound Ci3norisoprenoids by gas chromatography, and for 2-methoxy-3isobutylpyrazine (ibMP) by gas chromatography / mass spectrometry (Marais et al., 1996; 1999).
Sensory analysis
Wines of each treatment, region, season and replicate were sensorially evaluated for fruitiness and vegetative/asparagus/green pepper
intensities by a panel of six experienced judges. A line method was
used, i.e. evaluating the intensity of each characteristic by making a
mark on an unstructured, straight 100 mm line (Marais et al., 1999).
Statistical procedures
Seventy-two independent data sets consisted of three seasons,
three localities, two canopy treatments and four ripening stages.
Only 70 data sets were used, due to two missing plots. A 15-vine
plot was considered as an experimental unit. For each experimental unit the microclimatic measurements, such as the mean
maximum, mean minimum and average temperatures during a
ripening week, were calculated and served as independent variables. The average light radiations above and within the canopies
were also recorded as independent variables. The grape and wine
measurements (averages of three replicates), such as aroma
volatiles (monoterpenes, norisoprenoids and ibMP) and sensory
data (fruitiness intensity and vegetative/asparagus/green pepper
intensity) were recorded as dependent variables.
Pearson's correlation coefficients were calculated between the
above-mentioned independent and dependent variables and scat-
23
ter plots were examined for trends. After examining the scatter
plots, it was clear that the radiation variable showed a non-linear
trend. Therefore three additional terms were added (i.e. the
squares of the above- and within-canopy light radiation and the
interaction between them) before the data were subjected to the
stepwise regression procedures. For each dependent variable a
stepwise regression was performed with a specified significance
level of at least 5% for inclusion in the models, using SAS
(Version 6.12 ) statistical software (SAS, 1990).
For the above-mentioned analyses, the data were handled in two
ways. Firstly, all the data were statistically processed. Secondly,
the data obtained at ripeness (fourth ripening stage) only were
statistically processed, since wines were produced from grapes at
this stage.
RESULTS AND DISCUSSION
The final models produced by the stepwise regression procedures
are given in Table 1 and Figures 1 to 3 for the complete data set,
and in Table 2 and Figures 4 to 6 for the data of harvest week four
only. These coefficients correspond to significant correlations
between dependent and independent variables (data not shown).
The figures presented were selected with the main purpose of this
study in mind, i.e. to predict wine quality from easily-measurable
microclimatic parameters. Although ibMP was significantly
described by the interaction of above- and within-canopy radiation, only 43.4% of the variation could be explained by the model
(Table 1, Fig. 1). For fruitiness intensity 33.3% of the variation
was explained by maximum temperature and the above-canopy
radiation (Table 1, Fig. 2). The vegetative/asparagus/green pepper
intensity (complete data set) showed the best coefficient of determination, i.e. R2 = 68.8% (Table 1, Fig. 3). The above-canopy
radiation showed a greater effect than the within-canopy radia-
TABLE1
Coefficients of independent variables selected for model and standard errors. Models fitted to all the data (N=70).
Intercept
Variable
T min.
T max.
T aver.
A
W
AxW
Mono!
65.4387
±8.0075
Noris
37.8475
±5.9782
-0.5634
±0.2537
ibMP
91.8313
±17.5359
-2.8195
-14.8243
0.5092
±0.7455
±3.9360
±0.1616
21.9055
±10.4858
-1.0191
±0.4318
37.2%
43.4%
sl<0.01
2.1351
-15.6791
±2.6458
=
Total free monoterpenes {relative concentration)
=
=
=
=
Tota! bound monoterpenes and Cn-norisoprenoids (relative concentration)
2-Methoxy-3-isobutylpyrazine concentration (ng/L)
Fruitiness intensity (%)
Vegetative/asparagus/green pepper intensity (%)
=
=
=
Visible light radiation above the canopy (MJ)
Visible light radiation within the canopy (MJ)
Minimum temperature (°C)
Maximum temperature (°C)
Average temperature (°C)
Not selected
=
=
6.8%
sl=0.03
33.3%
sl<0.01
±0.3767
Noris
ibMP
Vagp
A
W
T min.
T max.
T aver.
_
R2
sl<0.01
Monot
Fi
W2
-2.3810
±0.3752
265.119
±29.648
Vagp
A2
-8.3895
2.9499
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2001
0.3043
±0.0590
0.5505
±0.2492
68.8%
sl<0.01
A Model for Predicting Sauvignon blanc Wine Quality
24
TABLE 2
Coefficients of independent variables selected for model and standard errors. Models fitted to the data from harvest week four only (N= 18).
Intercept
Variable
Monot
Noris
ibMP
T min,
T max,
T aver.
A
W
AxW
66.5851
-1.7250
—
—
—
—
±8.3672
±0.2792
—
R2
70.5%
sl<0.01
—
—
—
—
—
_
_
_
_
146.6720
—
—
—
-11.9510
—
—
0.2516
±0.1180
—
40.8%
sl=0.02
±55.4550
±3.1776
6.7709
±16.2588
—
—
—
1.5152
±0.6995
—
—
Vagp
313.451
±82.2622
—
—
—
-22.3616
±7.6806
—
_
—
—
0.4499
±0.1750
Monot
Noris
=
Total free monoterpenes (relative concentration)
=
Total bound monoterpenes and Cj3-norisoprenoids (relative concentration)
ibMP
=
=
=
=
=
2-Methoxy-3-isobutylpyrazine concentration (ng/L)
Fruitiness intensity (%)
Vegetative/asparagus/green pepper intensity (%)
Visible light radiation above the canopy (MJ)
Visible light radiation within the canopy (MJ)
=
Minimum temperature (°C)
=
=
=
Maximum temperature (°C)
Average temperature {°Q
Not selected
Vagp
A
W
T min.
Tmax.
T aver.
—
—
Wz
—
Fi
Fi
A2
22.7%
sl=0.046
—
65.0%
skO.Ol
Y = 91.83 - 2.819A - 14.824W + 0.5Q92AxW
R = 43.4%
Y = 21.9055 • 1.019T max. + 8.1351A
si < 0.01
R 2 = 33.3% si < 0.01
*• ^
ft
rM
'«Won(Mj,
"
^
-*"
FIGURE 1
Effect of above-canopy (A) and within-canopy (W) radiation
(between veraison and ripeness) on 2-methoxy-3-isobutylpyrazine concentration in Sauvignon blanc grapes.
FIGURE 2
Effect of above-canopy (A) radiation and average maximum
temperature (T max.) (between veraison and ripeness) on
the fruitiness intensity of Sauvignon blanc wine.
tion. The higher the average above-canopy radiation, the lower
the vegetative/asparagus/green pepper intensity of the wine (Fig.
3). This is in agreement with data presented by Marais et al.
(1999). Although natural shading plays an extremely important
role in Sauvignon blanc quality development (Marais et al.,
1999), models developed separately for the shaded and control
treatment data were more or less the same as for the full data set
and are therefore not reported.
Models arising from the data of ripening week four (harvest
time) only are presented in Table 2. As much as 70.5% of the vari-
ation in monoterpene levels was explained by the average maximum temperature for the week in which the grape samples were
taken. Monoterpenes may contribute to the flower-like nuances of
Sauvignon blanc wine, but are probably less important than the
cultivar-typical methoxypyrazines. The negative coefficient indicated that the higher the maximum temperature, the lower the
monoterpene concentrations in the grapes, which is in agreement
with results reported by Marais et al. (1999), There was not
enough evidence, i.e. no variables were selected, to fit a model on
the norisoprenoids in the grapes. 2-Methoxy-3-isobutylpyrazine,
S. Afr. J. Enol. Vitic., Vol. 22, No. 1, 2061
25
A Model for Predicting Sauvignon blanc Wine Quality
35
Y = 146.672 - 11.9510A + 0.2516A
Y = 265,119 - 15.6791A 4- 0.3043A
- 8.3B95W + 0.5505W
= 68.6% si < 0.01
g
30
Is
25
R
= 40.8% si = 0.02
Q.D)
IT 20
«s
««
A£
15
10
5—
12
14
16
18
20
22
24
26
26
30
Above-canopy radiation (MJ)
FIGURES
Effect of above-canopy (A) and within-canopy (W) radiation
(between veraison and ripeness) on the vegetative/asparagus/
green pepper intensity of Sauvignon blanc wine.
FIGURE 4
Effect of above-canopy (A) radiation at harvest (week 4) on
2-methoxy-3-isobutylpyrazine concentration in Sauvignon
blanc grapes.
70
100
Y = 313.451 - 22.3616A + 0.4499A
60
R
80
= 65.0% si < 0.01
50
*
60
40
S."
30
.*•
iS5
40
20
Y = 6.7709 + 1.5152A
10
R = 22.7% si = 0.046
12
14
16
18
20
22
24
26
28
30
12
14
Above-canopy radiation (MJ)
FIGURES
Effect of above-canopy (A) radiation at harvest (week 4)
on fruitiness intensity of Sauvignon blanc wine.
fruitiness intensity and vegetative/asparagus/green pepper intensity showed a significant response to the above-canopy radiation
only (Figs. 4, 5 and 6, respectively). Again the vegetative/asparagus/green pepper intensity variation was best explained by a quadratic response of above-canopy radiation with 65.0%, and a minimum turning point of 24.9% for the above-canopy radiation. In
spite of the fact that only 18 data points were applied for ripening
week four, results obtained for vegetative/asparagus/green pepper
intensity (65.0%, Table 2) were close to those of the full data set
(68.8%, Table 1).
16
18
20
22
24
26
28
30
Above-canopy radiation (MJ)
FIGURE 6
Effect of above-canopy (A) radiation at harvest (week 4) on
vegetative/asparagus/green pepper intensity of Sauvignon
blanc wine.
CONCLUSIONS
There is a significant relationship between gas chromatographically-analysed grape aroma components, sensorially-evaluated
wine quality parameters and microclimatic data. Models are presented, one of which can predict Sauvignon blanc wine quality
(cultivar-typical vegetative/asparagus/green pepper intensity ^
from above- and within-canopy radiation data, collected ovei
grape ripening, with a fairly high degree of accuracy. It is therefore possible to predict wine quality from easily-measurabh
microclimatic data. The results of this investigation wert
S. Afr. J. Enol. Vitic., Vol. 22, No. 1,2001
A Model for Predicting Sauvignon blanc Wine Quality
26
obtained under specific South African conditions and it is not
claimed that they are valid under all conditions. Nevertheless,
they can be considered as a contribution towards wine quality
prediction. Future research is necessary to test and refine this
model for application under different environmental conditions.
Holgate, A., 2000. Berry colour index assay - application and interprelation of the
assay as an objective measure of red wine grape quality in a commercial vineyard.
Proc. 5th Int. Symp. Cool Climate Vitic. & Enol., 16-20 January 2000,
Melbourne, Australia. In press.
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