Agriculture Reference
In-Depth Information
rate, combined with flow control valves, water can be differentially applied to
parts of a vineyard according to the available water and drainage properties of
the soils. A map of vineyard soil variation showing soil textures and depths allows
RAW, DAW, and PAW values to be estimated, as shown in table 4.4 in chapter 4.
None of these applications of PV will convince a winegrower of the need to
act unless they result in a better product and making more profit, with minimal
environmental impact. Hence, the main interest shown by winegrowers in PV is
in mapping yields, vine vigor, and indices of fruit ripeness, and using this infor-
mation to plan diferential harvesting in time or space. To this end, the topic
Precision Viticulture (Proffitt et al., 2006) gives examples of where zones of differ-
ent vine vigor within blocks were identified before harvest and the fruit in these
zones was separately harvested and vinified. More recently, Bramley et al. (2011)
give examples of the potential benefits to growers from the sale of their fruit
to wineries, through selective harvesting based on remote sensing of vine vigor
before harvest. The realization of these benefits will depend on several factors
such as access to technical expertise to interpret vine vigor maps, a commitment
to collecting such data for several seasons, the ability to harvest parts of blocks
separately, and the willingness of wineries to pay an adequate price for higher
quality fruit (Krstic, 2012).
An increasing number of small producers are adopting what might be called
a de facto approach to PV. For example, Lloyd Brothers' vineyard of 12.5 ha of
Shiraz vines in McLaren Vale region, South Australia, was planted in four blocks
from 1998 to 2000 and originally treated as one commercial block with no regard
to soil and other environmental variations across the blocks. Now, however, the
top priority is to make small batch wines from selected rows within a single block.
As Jodie Armstrong (2007) said, “The wines reflect the terroir of the slope with
fruit from the top rows exhibiting a rich, ripe, dark berry character. The section
in the middle of the slope provides more juicy fruit flavors, with rows from the
bottom of the block providing a perfumed blending agent. We typically view the
vineyard in three sections: super-premium, premium and table wine.”
Managing Soil Water
Outside most of the Appellation d'Origine Contrôllée regions of France, vine-
yards have the option of managing the water supply to vines to achieve particular
yield and quality objectives. As described in chapter 4, such water management
can be achieved through RDI, partial root zone drying (PRD), or sustained deficit
irrigation.
Research in Australia, California, and Spain has shown that a soil water deficit
( SWD ) can have a positive effect on fruit quality, especially of red grapes, but the
size of the deficit (determining the degree of stress induced) and its timing must be
appropriate. Expressed in terms of available water, the SWD should not exceed the
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