Agriculture Reference
In-Depth Information
In summary, Carbonneau (2009) maintains that tradition has tended to
determine vine spacing, with close planting the norm in Old World vineyards,
except in very dry areas, and wider spacings used in the larger-scale, more vigor-
ous vineyards of the New World. French Appellation d'Origine Contrôlée regula-
tions, and those of comparable organizations in other Old World countries, limit
the quantity of wine produced per ha. Whereas such restrictions on fruit or wine
yields were not previously imposed in New World countries (e.g., Australia), in
recent years many wineries have imposed limits on the tonnes of fruit per ha.
At the same time, planting densities have increased, which has generally resulted
in more efficient exploitation of the soil by the vines. According to a winegrow-
er's objectives, vine vigor and yield are now more effectively controlled by choice
of rootstock, low input of nutrients and water, use of cover crops, and canopy
management (particularly pruning), the last of which is the subject of the topic
Sunlight into Wine
by Smart and Robinson, first published in 1991, with the last
reprinting in 2013.
Irrigation and Drainage Design
In France, irrigation cannot normally be used if the wine produced is to be mar-
keted under an Appellation d'Origine Contrôlée label. In other countries, wine-
growers who want to produce
terroir
-type wines at the premium end of the market
will tend to use irrigation sparingly or not at all. However, in many regions of
Spain, Australia, South Africa, Chile, and California, where the summers are hot
and dry, irrigation has become an essential part of vineyard management. Surface
or subsurface drip irrigation is preferred to overhead spray or furrow irrigation
because it permits greater control over the water applied and minimizes water loss
through evaporation (see “Irrigation Methods,” chapter 4).
Vine water use can be made more efficient if the application of water takes
account of soil properties such as depth, drainability, and water-holding capac-
ity (see table 2.2). Although organic matter can increase a soil's water-holding
capacity, its effect is confined to the topsoil and is more significant in sandy soils
than clay soils. For example, Kay et al. (1997) used pedotransfer functions to
show that an increase in soil organic carbon (say, from 0.7% to 1.7%) would
increase plant-available water only by 2 to 4 mm per 10 cm depth of soil. The
influence of various factors on plant-available water is discussed more fully in
chapter 4.
If a soil survey reveals zones where one or more of the critical soil properties are
substantially different, the irrigation design should be adjusted through the spac-
ingofdrippersandtheirdeliveryrate(seebox2.3).Pressureself-compensating
drippers allow water output per dripper to be as uniform as possible along a pipe-
line and also over undulating ground. Keeping the pipe system as full as possible
