Agriculture Reference
In-Depth Information
classification for viticulture should be created, and, if applicable to a larger area,
the classes correlated with a national classification (e.g., Soil Taxonomy in the
United States).
A soil survey can provide detailed information on soil variation, usually expressed
in the form of a map. Before this is begun, data from remote sensing, geology,
and vegetation maps should be examined to identify possible soil types and their
distribution. Inferences drawn from aerial photographs or satellite images should
be ground-truthed. Digitized data can be entered into a GIS. These data can be
augmented with that acquired by proximal sensing at a high density of observa-
tions (e.g., a salinity survey by EM methods).
The soil is best examined in pits dug to depths of 1.8-2 m, preferably on a 50-
50-m grid (approximately 6 pits per ha). Information on soil variation between
pits is obtained by conducting a free survey , using an auger. The location of all
observation points should be determined by a GPS, so that data can be entered
into a GIS. The density of sampling on the ground determines the scale at which
the soil is mapped.
Soil horizons should be identified and the following key properties measured: soil
depth, stone content, texture and texture change with depth, color (including any
mottling or gleying), aggregate consistence and whether aggregates are stable in
water, content and depth of any CaCO 3 , and salinity (measured by EC ).
Detailed knowledge of soil variation can be used to plan the location of specific
cultivars, the irrigation layout, and the implementation of precision viticulture.
A Soil Factor Map (e.g., with soil pH distribution) can be linked to a Soil Im-
provement Map (with recommendations on liming) and also to a Cost of Repair
Map in a GIS.
Biological factors to be considered are the past cropping history and presence of
pests, especially phylloxera and nematodes, and soil-borne diseases. These will in-
fluence the choice between own-rooted vines and rootstocks.
If irrigation is needed, the quantity and quality of water supplies should be as-
sessed. Quantity estimates should be based on peak midsummer demand. The EC
of irrigation water should generally be 1 dS/m, except where salt-tolerant root-
stocks such as Ramsey, 140Ru, or 99R are used. Where natural supplies of water
are scarce, recycled water (“grey water”) may be considered.
Land slope and aspect are important site factors because they influence soil prop-
erties, the amount of solar radiation received, the choice of row orientation, and
temperatures. Proximity to large water bodies moderates the diurnal temperature
range and seasonal temperature extremes.
Preplant soil preparation generally involves deep ripping, to break up layers that
may impede roots or drainage, and fertilizing. Fumigation may be carried out if
the nematode population is high. This is done during late summer and autumn,
and a cover crop is sown to protect the soil during winter until the vines are
planted.
Preliminary survey data on geology, mesoclimate, and soil are used to evaluate site
potential , and hence the likely vigor of the vines. Depending on this potential,
vine spacing (both between rows and in rows) is then chosen to satisfy the dual
objectives of highest quality fruit from each vine and optimum yield per ha of this
fruit. Vine vigor is also influenced by factors such as trellis type, canopy manage-
ment, cover crops, fertilizer, and water supply.
Search WWH ::




Custom Search