Agriculture Reference
In-Depth Information
Grape and Wine Quality Factors Associated with Three Common Soil Types
in St. Emilion-Pomerol
Table 9.2
Deep Sandy Topsoil
Shallow Sandy
Over Sandy Clay
Topsoil Over Very
Deep Gravelly Soil,
Subsoil, with a
Heavy Clay Subsoil,
Grape or Wine
Very Well Drained
Water Table
Gley Features
Property
Soil Type 1
Soil Type 2
Soil Type 3
Total acidity (mmol charge/L)
58
62
64
pH
3.87
3.74
3.80
Alcohol concentration (%)
12.3
12.4
12.8
Anthocyanins (mg/L)
510
350
510
Total phenols (D280) a
41
35
49
Total tannins (g/L)
2.0
1.7
2.4
a Measured by absorbance of light of 280-nm wavelength
Source: Data from van Leeuwen et al. (1998)
soils is an asset. In Central Médoc, where most of the First and Second Growths
are produced, the soils are deeper and contain more silt and clay. The best wines
are produced from the tops and upper slopes of the gravelly mounds (up to 30 m
high in Pauillac), whereas the second and lower order growths are produced from
the lower slopes and hollows where the soil does not drain as well. Not only does
the depth to the permanent water table vary with the topography (and season),
but perched water tables can develop over lenses of impermeable clay at different
depths in the profile, as shown in figure 9.4.
Water movement shown in the cross section of a gravel mound in the Médoc (redrawn
from Wilson 1998).
Figure 9.4
Rainfall
Surface
runoff
Perched water table
(tr a nsient)
Old erosion
surface of
Tertiary strata
Clay lens
Sp ring
Mud flats
Fractured
limestone
Gironde
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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