Agriculture Reference
In-Depth Information
Comparison of Yield, Grape Composition, and Wine Quality
in Dryland and Irrigated Vineyards
Table 9.1
Dryland: Barossa Valley (Warm)
Irrigated: Berri and Loxton in the Riverland
and Eden Valley (Cool)
(Hot)
Yields (t/ha)
2.5-7.5
15-25
Grape composition (Shiraz)
Lower pH, lower K, lower Cl,
Higher pH, higher K, higher Cl,
higher titratable acidity
lower titratable acidity
(as tartaric acid)
(as tartaric acid)
Wine properties (Shiraz)
Lower pH, higher titratable acidity
Higher pH, lower titratable acidity
(as tartaric acid)
(as tartaric acid)
50-400% more color than in Shiraz
Less color than in Barossa and Eden
grapes grown under irrigation
Valley wines
Wine properties (Riesling)
No consistent significant differences in pH or titratable acidity between regions, but better
aroma and taste scores for the wines produced from dryland vines
Source:
Data from Rankine et al. (1971)
trial from 1977 to 1998 grew the varieties Muller-Thurgau and Silvaner in large,
1-m-deep containers filled with soil from seven different parent materials. To elim-
inate the climatic variable from
terroir
, the containers were placed in a typical vine-
yard in the Franken region of Germany, with the aim of isolating the soil effect
on wine character. The wines from the trial were compared with wines made from
the same varieties in the original locations whence the soils were collected. Al-
though there were differences in grape yield, the effect of soil type on the senso-
rial traits of the wines was very limited.
One problem with this type of experiment is that the root environment in a
confined cubic meter of soil would have been very different from that of roots
free to explore a larger soil volume in the field. Further, the hydrologic regime of
each soil would have been changed by its removal from the field and repacking
in a container. This point is emphasized by the results of Campostrini et al. (1996)
in the Vino Nobile de Montepulciano territory of Italy. Working on soils derived
from calcareous parent materials, with variable drainage and erosion, they found
little relationship between fruit quality and wine personality (or “typicity”) and
the
AWC
and air capacity of the soils. Obviously, there is more to determining
the hydrologic influences of soil on vines than can be expressed in laboratory mea-
surements of
AWC
and air capacity.
To date, the technical approach to defining
terroir
has not been particularly
successful. However, the application of new techniques in remote and proximal
sensing, which allow the rapid collection of data on soil, cultural methods, and
yield at very high observation densities (section 8.2.1), offers the opportunity to
better define quantitative relationships between the soil and wine quality. Mean-
while, the lack of success in quantifying the key factors of a
terroir
is an advan-
