Agriculture Reference
In-Depth Information
8
Site Selection and Soil Preparation
Soil Is Important in Site Selection
8.1
At the Pine Ridge winery in Napa Valley, California, a sign lists six essential steps
in wine production. The first step reads
Determine the site—prepare the land, terrace the slopes for erosion control,
provide drainage and manage soil biodiversity.
Determining the site means gathering comprehensive data on the local cli-
mate, topography, and geology, as well as the main soil types and their distribu-
tion. Traditionally, site determination was done using the knowledge and experi-
ence of individuals. Now it is possible to combine an expert's knowledge with
digital data on climate, parent material, topography, and soils in a GIS format to
assess the biophysical suitability of land for wine grapes. Viticultural and soil ex-
perts together identify the key properties and assign weightings to these proper-
ties. An example of an Analytical Hierarchy Process is shown in figure 8.1. In this
approach, both objective and subjective data were pooled and evaluated to decide
the suitability of land for viticulture in West Gippsland, Victoria. In this region
with a relatively uniform, mild climate, soil was given a 70% weighting, and the
important soil properties were identified as depth, drainage, sodicity, texture, and
pH. But in other areas, with another group of experts, a different set of key prop-
erties and weightings may well be identified. For example, a similar approach used
in Virginia, in the United States, gave only a 25% weighting to soil and 30% to
elevation (which affected temperature, a critical factor governing growth rate and
ripening) (Boyer and Wolf 2000).
This kind of approach can be refined to indicate site suitability for a partic-
ular variety within a region of given macroclimate. For example, Barbeau et al.
(1998) assessed the suitability of sites in the Loire Valley, France, for the cultivar
Cabernet Franc, using an index of “precocity.” Such an index is related to the
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